Battery Powered Radio Control Tips

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Why Run Trains On Battery Power?

The main reason to go to the trouble and expense of running trains on battery power is to avoid cleaning or even wiring the track. The issues of track cleaning really can be a big deal. Adding radio control to a battery power system adds the capability of command control, a highly desirable feature.

In some environments, any kind of track power is flatly impractical due to a number of conditions. In other environments, track power works quite well and is certainly less expensive than implementing battery power. If track power works and the added flexibility of command control is desired, then consider adding Digital Command Control (DCC) to an existing track powered system. Both battery R/C and DCC allow command control at something like the same total expense depending on the number of locomotives converted. DCC tends to be more costly up front and less costly incrementally. If a large number of locos are converted, DCC becomes less expensive than battery power. If you go that far, the money probably doesn't mean that much to you anyway. If track power works in your current setup, DCC will work too for all but the smallest locos and it will add all the advantages of command control in a flexible and expandable fashion. Walk around radio control with DCC is also highly effective if not a little costly up front. Due to the limited number of power pickups on small locos, they will require fairly clean track to run and might best be converted to battery power anyway. A battery powered loco will run fine along with DCC locos. MU operation with battery and DCC in the same consist would have the same problems as MU control of two independently controlled battery powered locos.

There are few economies of scale for fully self contained battery power. If you are just starting out, using battery power allows you to use less expensive track and to avoid track wiring altogether. Using a trail car to hold the batteries and radio gear tends to mitigate the cost and complexity of battery power but with the inconvenience of hauling the trail car around all the time.

A comparison of the features and liabilities of track power, battery power, DCC and live steam can be found in my Power Tips page.

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Train Control Methods

The majority of the methods that are in use to control model trains fall into two general categories. These are called cab control and command control.

Cab Control is the most common system and conceptually the most simple even though there are incredibly complex implementations out there. Your typical starter set with a power pack and a circle of track is cab control in its least complicated form.

Cab control simply means that one or more power packs of some kind are used to control one or more sections of track. All the engines on a particular section of track are controlled together by the power pack, or cab, that is currently connected to that section. Often an elaborate switching system is wired to sequentially route power to sections of track such that an individual train remains controlled by a single power pack as it traverses many sections of track.

Cab control has the advantage of simplicity and low cost. No fancy electronics are necessary to make it work. No modifications to locomotives are required. Troubleshooting is relatively easy.

Cab control has two serious disadvantages. One is that different trains on a single section of track respond to the same commands. This severely limits operational flexibility. The second is that the methods that are used to switch control between track sections usually require a lot of manual intervention in the form of flipping switches. This can get to be a real drag and can seriously detract from the enjoyment of running trains.

Command Control gets around these two problems through circuitry that allows engine control commands to be sent directly to an engine (or group of engines in an MU consist) independently of all other engines. There are many implementations of command control, many involve direct radio control of a track powered, live steam, or battery powered locomotives. Others transmit commands to a locomotive via the track itself in one of several different formats. Command control allows each locomotive to be run all over a layout without worrying about flipping cab switches. Individual trains can run at different speeds or even different directions anywhere on the layout without regard to other trains (cornfield meets notwithstanding).

One common feature of command control is that each engine carries some form of command receiver that controls the motor (or throttle in the case of live steam) of a locomotive in response to commands directed to that particular locomotive. This adds a level of electronics complexity not usually found in cab control.

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Why Use Command Control?

Even though command control and its components are usually fairly complex, it offers operational advantages that are hard or impossible to achieve with cab control. Also, for those of us that are technically inclined, it has great toy value. Even though the systems are electronically complex, the various manufacturers have done a credible job of making their systems installable and usable by even those individuals who consider themselves "technically challenged."

Command control allows multiple trains to run anywhere on a layout without regard to the speed, direction or position of other trains, collisions excepted. The operator can concentrate on running his train without worrying about the method that it takes to do it.

Command control combined with battery power allows a degree of freedom not possible with any kind of track powered trains. It allows the trains to operate on less expensive track that never needs cleaning. In some areas of the country, track contamination is such a serious problem that track powered trains are nearly impractical.

Battery power carries a couple of liabilities, and they may be considered serious by some. First, a fairly large battery is required. It can be carried inside some engines, but others require that the battery be carried in a trail car. Batteries have a limited energy storage capability and must be recharged. Typical battery run times vary and can range from less than an hour to several hours. Batteries don't last forever and need to be replaced occasionally. Multiple unit control is a problem as it is difficult to control multiple engines together to make them share the load properly. Some may consider this to be a realistic operating challenge to be met because that is the way it was done with real steam engines.

Overall, battery power with some form of command control can be considered a very successful system. It has proven itself well and operators that have converted to battery power seem ill inclined to convert back.

Track powered command control also has advantages and its own liabilities. With track power available, locomotives can run continuously with long, heavy trains and with all manner of power hungry accessories running and never run down. With some track power command control systems, multiple unit control is implemented easily and effectively. In this case it works much the same as prototype MU diesel control. The engineer has all the locomotives under the control of his throttle. Speed control and power sharing between the locomotives is handled automatically.

Track power still requires that the track be in good condition and at least reasonably clean or it just won't work. In some areas of the country, track cleaning seems to be a minor problem and track powered systems work quite well.

With either battery powered command control or track powered command control, operability of trains is materially improved. I feel that this improved performance is worth the cost and hassle of implementing command control of some kind. Which kind would work best for you will depend mostly on which of the downside issues bother you most.

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Comparison of Battery R/C and DCC

Command control is implemented well with both DCC and battery R/C systems. Each has strengths and weaknesses and both are better than regular track powered cab control.

I have elected to implement a mixed system as battery R/C and DCC can coexist nicely. Neither system does all things well and each does some things better than the other. In those areas of the world where track power does not work very well, you are either stuck cleaning your track often or going full over to battery R/C.

DCC Vs Battery R/C
Characteristic DCC Battery R/C
Track Wiring and Continuity Pro

Needs only one track connection

Not needed at all


Needs some wiring

Needs good rail joints


Track Cleaning Pro

Larger or MU locos tolerate dirty track well

Immune to any kind of grit, oil, oxide, or bug guts

Immune to rail joint continuity


Smaller locos do not get steady enough power on dirty track

Still have to clean up leaves, sticks and twigs

Still have to clean up leaves, sticks and twigs

Runtime Pro

no limits

Usually long enough for operating sessions with smaller locos



Larger locos and heavy trains can limit runtime to less than an hour

Not suited to continuous operation

Accessory Power Pro

Can power accessories at constant intensity whether the train is moving or not

Accessory operation does not impact run time

Can power accessories at constant intensity


Booster has current limits, must be sized adequately

Accessories drain the batteries shortening runtime

Speed Control Pro

Excellent with 28 or 128 step decoders

Mismatched locos can be matched with speed tables

Usually Excellent (depends on RX design)


14 step decoders have too few speed steps

Can be difficult to speed match locos operating in MU consists

MU Operation Pro

Easy to set up

MU locos do not get out of speed sync




locos controlled by the same TX can get out of sync

Operators of double headed non MU locos have to pay attention to keep them from bucking/dragging

Cornfield Meets (collisions) Pro




Operators have to pay attention


Reversing Loops, Wyes and Turntables Pro

Auto reversing boosters handle reversing structures automatically

The track is not powered so no precautions or special considerations are needed at all


Needs special boosters or autoreversing modules and extra power feeds to accommodate reversing structures


Cost Pro

Lower incremental cost per loco

Lower initial cost

Low incremental cost if a trail car with both batteries and RX installed is used


High initial cost for cab, command station, radio gear (if used), booster and power supply

Profession installation is atypical, DIY is more common

Higher incremental cost for dedicated installations

RX typically more expensive than a DCC decoder

Professional installations can be very expensive

Installation Difficulty Pro

Easier, decoders are typically smaller than radio receivers

No need to find room for batteries

No need for a charger jack or power switch

Relatively easy if a trail car is used


Loco modifications are required

Motor leads must be separated from all other wiring

Accessories should be run from the decoder or a switch provided to disconnect them during decoder programming

Loco modifications are required

Power pickups should be disconnected

Dedicated installations can be a challenge to find room for batteries, RX, power switch and charge jack

Battery Useful Life Pro

No problem, no batteries

Batteries can last 500 to 1000 charge cycles



Batteries are expensive

Sometimes they fail much sooner than they should

Abuse of batteries can result in almost immediate failure or degradation

Transportability to Other Layouts Pro

NMRA compliant decoders can run on regular track power

Can run without difficulty on other DCC equipped layouts

No problem, locos will run anywhere


Analog conversion may not be totally smooth (depends on decoder design)

Accessories may or may not work properly when running on regular track power

Can't run at all on a unpowered layout


Walk Around Control Pro

Some DCC systems use radio throttles to allow walkaround control

Radio range on some systems can be increased to arbitrary distances with multiple receiver diversity reception

Has walk around control by nature


Radio gear is expensive

Additional receivers to allow wider coverage are either expensive or not available (depends on the type of the radio gear and command station)

May have limited range due to on board antenna restrictions

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On Board Radio Control Gear

There are several different proprietary radio command control systems available. Each of these systems has addressed a particular set of user needs and each seems to work as they have all been successful in the market and their users tend to proclaim their features. All of these systems provide control ranges of 50 to 100 feet or so in the best case. Depending on installation restrictions, the range can be less.

Each of these systems is self contained and completely captive to a particular manufacturer. Each system is totally incompatible with all of the other systems except for different systems can run on the same track at the same time. Each of these systems is also currently incompatible with DCC control except that some of them will accept the DCC track signal as a source of power in place of a battery. A properly configured battery powered loco will run on any track even if DCC or another kind of track power is being used at the same time.

There are infrared control systems available as well, but IR tends not to work so well out of doors due to interference from a relatively larger IR source in the sky.

More information on each system can be found at the manufacturer's web sites. These sites can be accessed with the links at the beginning of each paragraph.

The Train Engineer by AristoCraft operates at 27 MHz or 75 MHz and allows on board battery power, constant track power, or regular track powered operation. It has a 10 amp capacity for regular track power and 2.5 amp capacity for on board power. The system includes accessory receivers and adapters that can be used to operate onboard or stationary accessories. Onboard receivers will accept DCC for power so that the TE and DCC can coexist to some extent. The system is designed to allow a small number of transmitters to address a large number of receivers. Each transmitter can easily address 2 or 10 (depending on the transmitter version) different receivers. 20 or 100 different receivers (again depending on the version) can be addressed with somewhat more difficulty.

Locolinc by Keithco operates at 75 MHz. This system allows on board battery, constant track power, or battery backup constant track power operation. Accessory control is available for both on board and stationary accessories. Locolinc is probably the most elaborate and expandable proprietary command control system. The Locolinc system is also configured to allow a small number of transmitters to control up to 64 different receivers.

RCS offers a 27 MHz radio command control system that can operate from batteries, constant track power or a trackside receiver can be used for conventional track power. The RCS transmitter is easily the smallest of the bunch and fits easily into a shirt pocket. The RCS system allows accessory controls. The system is designed for dedicated operation, one transmitter is usually paired with one receiver. 96 pairs are allowed.

Reed's Hobbies Instant R/C is another 75 MHz system that uses inexpensive AM type radios for control. This system is usually configured for battery power only. It allows limited control of onboard accessories and usually requires one transmitter per receiver. This system may not be available anymore.

CVP AirWire is a recent 900 MHz system. AirWire uses the DCC command packet format, but it is transmitted from a handheld throttle directly to an AirWire compatible decoder on the loco. The CVP Airwire decoder is a 10 amp job that runs from 12 to 28 volts DC and will drive a 10 amp load. It will also drive an accessory DCC sound decoder via a special DCC output. This system isn't cheap, but it apparently works. One transmitter can control many thousands of locos, but only one at a time. QSI also makes an AirWire compatible receiver that can be connected to their DCC sound decoders to do pretty much the same thing as the CVP decoder except that the QSI decoder has sound but only 3 amps of motor control capability. One significant advantage of the 900 MHz systems is that the antenna needs to be only 3" long.

The key thing to remember about these systems is that they are proprietary. The components for these systems are available only from their manufacturer (with the exception of Reed's transmitters) so that if the manufacturer goes out of business, chooses to stop manufacturing the system or chooses to stop expanding the system, you won't be able to expand further without buying bits and pieces on the used market.

With radio control, it is NOT necessary to decide on one brand and stick with it. There can be some economy of scale by using only one brand, but it typically isn't a big factor. If you find that you are not completely pleased with one type, you can do your next conversion with another type. The first one will still run and be useful in the presence of another kind of system.

Of the five systems listed above, I have extensively used only one of them, the Aristo Train Engineer. Since I don't have experience with the others, I don't feel that it is fair to judge any of them. If you elect to go the radio control route, you'll have to investigate the possibilities and select among them. They all work.

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Rechargeable Battery Selection

There are many different rechargeable battery technologies, but only a few of the are suitable for use in large scale locomotives. For example, the most common rechargeable battery is the wet lead acid type used in car and motorcycle batteries. While this kind is rugged and relatively cheap, these batteries are typically too large and don't tolerate being turned upside down. The smaller, less powerful "gel cell" is used instead because it can be operated in any orientation.

The four most suitable battery technologies (listed in order of increasing energy density) are:

Each of these types has distinct advantages and disadvantages. None is ideally suited to all applications. The important characteristics of a rechargeable battery are listed below and a table comparing those characteristics is shown below the list.

A cell is an individual chemical unit and cannot be subdivided. Cells are manufactured in many shapes and sizes. A battery is a collection of cells wired in series, parallel or series-parallel. Series connection is by far the most common. Multiple cells are very often provided in a single housing. A 12 volt car battery is composed of 6 individual cells wired in series. The cell voltage is determined by the chemistry of that particular kind of cell.

Energy Density describes how much energy a battery can store by either volume or weight. Most of the battery technologies are fairly heavy. This does not matter a great deal in train service. The more important characteristic is by volume because we are usually more restricted by the space available to install batteries than by what they weigh. When installed in a locomotive, weight is good because it aids traction.

Shape Factor describes the physical form factor in which a battery is available. Batteries available as individual cells can usually be arranged to fit in constrained spaces. Large rectangular batteries don't fit in nearly as many places.

Cell Voltage determines how many cells will be needed to create a battery of sufficient voltage to do its job. This net voltage will vary depending on the characteristics of the loco being converted and on operating preferences, but will usually range between 12 and 18 volts. To determine what voltage a particular loco will need, run in on regular track power at the maximum speed that you want to obtain. Measure the track voltage and add 2 of 3 volts to account for losses in the motor controller. Pick the number of cells required based on the voltage per cell of the technology that you select. In the case of gel cell batteries, you will usually be picking either 12 or 18 volts. For preconfigured NiCad packs, you get either 7.2, 9.6, 14.4 or 19.2 volts. For individual NiCad or NiMH cells, you can select any voltage in 1.2 volt increments. Also note that most of the radio receivers have a minimum input voltage. For example, the Train Engineer RX wants at least 14 volts but it will work with complaint down to 12 volts.

Cell Capacity is usually rated in Amp-hours or milliAmp-hours. This is the actual electrical capacity of a battery or cell. A 1 Amp-hour battery can supply 1 amp for 1 hour or 0.1 Amp for 10 hours. A milliAmp-hour is 1/1000th of an Amp-hour. Cells that are wired in series to achieve a higher voltage have the same Amp-hour rating as an individual cell. Cells wired in parallel have the same voltage as an individual cell but the capacity of the resultant battery is multiplied by the number of cells. An individual cell can achieve high capacity through large size or by being manufactured using a high energy density technology or both.

Internal Resistance determines the peak current that a battery can supply. Very low internal resistance is important for high peak current applications like starting a car, running a power tool or R/C race car. At the moderate and more steady currents that trains draw, this characteristic is less important.

Discharge Characteristic describes how the cell voltage degrades as a function of depth of discharge.

Special Discharging Precautions relates to any special care that must be taken in discharging a battery. Improper discharging can significantly reduce a battery's useful life.

Special Charging Precautions relates to any special care that must be taken to properly recharge a battery to full capacity without damaging the battery. Improper charging can significantly reduce a battery's useful life.

Shelf Life describes a battery's ability to sit, in a charged or discharged state, out of service. Some batteries tolerate storage well, some do not.

Cost is an important factor. Not surprisingly, the batteries that are overall better suited to model railroad use tend to be more expensive.

Rechargeable Battery Comparison
Characteristic Gel Cell NiCad NiMH Lithium Ion
Energy Density by Weight




Very High

Cells are lighter than other types for the same volume

Energy Density by Volume




Very High

High cell voltage results in very high density by volume

Shape Factor

Usually rectangular

Usually 3 or 6 cells per enclosure

Can be purchased in cylindrical format

Can be purchased in flat format

Virtually always in cylindrical format

Multiple cell packs are collections of cylindrical cells

Cells can be purchased tabbed for easier pack assembly

Virtually always in cylindrical format

Multiple cell packs are collections of cylindrical cells

Cells can be purchased tabbed for easier pack assembly

Almost always sold as single cylindrical cells

Cell Voltage

2 volts (average)

1.2 volts

1.2 volts

3.6 volts

Cell Capacity

typically 2 to 4 Ah

can be much larger in cases too big to really use in large scale trains

0.2 to 0.3 Ah in AAA size

0.5 to 0.9 Ah in AA size

1 to 2 Ah in C size

4 Ah in D size (some D cells are really C cells in a D sized case)

0.5 to 0.7 Ah in AAA size

1 to 1.7 Ah in AA size

2.2 Ah in C size, but hard to find

up to 0.8 Ah in AA size, but at higher voltage than the other types so more energy is actually stored by volume and weight

Internal Resistance


Very Low



Discharge Characteristic

Gradual, the cell voltage starts at 2.3 volts and rapidly decays to about 2 volts per cell then decays slowly throughout the rest of the discharge

Starts at 1.25 volts and remains above 1.2 volts for the first 50% of the discharge

As the voltage reaches 1 volt per cell, it begins to collapse rapidly

Starts at 1.4 volts but rapidly decays to about 1.2 volts and remains about 1.2 volts for the first 50-80% of the discharge

As the voltage reaches 1 volt per cell, it begins to collapse rapidly


Special Discharging Precautions

Doesn't like to be flattened

Do not discharge to less than 1.6 volts per cell

Do not allow the cells to sit discharged or they will sulfate and fail

Prefers to be discharged heavily to 1 volt or less per cell

Can be stored charged or discharged

Can be discharged by any amount down to 1 volt per cell

Can be stored charged or discharged


Special Charging Precautions

Indefinite constant current charging acceptable at 10% capacity

Can be fast charged but overcharging may result in overheating and eventual venting

Indefinite constant current charging acceptable at 10% capacity

Can be fast charged in 1 hour with a "smart" charger

Charger must detect both delta V and temperature

Indefinite constant current charging acceptable at 10% capacity

Can be fast charged in 2-3 hours with a "smart" charger

Charger must detect both delta V and temperature

Cannot be trickle charged

Requires special charger that operates in both constant current and constant voltage modes and regulates charge voltage to 1% or better

Shelf Life

Good, can retain a large percentage of a charge for months


Crystallization of the battery due to improper usage can seriously reduce the shelf life

The most common failure mode is the inability to hold a charge once taken, a nearly failed battery may hold a charge for only hours

Fair, cells typically loose 1% of their capacity per day of storage


Less than 10% capacity loss per month


Lowest per Ah capacity

Enough to run a train might cost $20

More Expensive

AA cells run from $0.75 to $2 depending on capacity and source

More Expensive

AA cells run from $2 to $4 depending on capacity and source


$10 per cell or more

hard to find in bare cell configurations

tabbed AA cellThis is a tabbed NiMH AA cell that is suitable for use in a large scale loco. A pack of 10 to 15 of these cells would be needed. Because the cells are separate, they can be packed in any available place and wired together. The cylindrical cells can be easily packed into cylindrical arrangements to fit within a boiler or saddle tank. They can also be stacked like cord wood to fit into rectangular areas. Similar cells are available in the AAA size for really tight installations. Tabbed NiCad cells are available at about half the cost, but usually at half the capacity too.

6 volt gel cellThis is a typical 6 volt gel cell battery with a 3 Ah capacity. It is very large and rectangular and will only fit in a loco with a very large body (such as an F unit) or in a trail car. Three of these batteries would typically be needed to run a train. This gel-cell battery is 5 1/4" long by 1 5/16" wide by 2 5/16" high and weighs 1-1/2 lbs.

nicad packsNiCad batteries are well suited to applications that require high peak currents, like R/C cars and power tools. The battery in front is a standard R/C car "sub-C" 7.2 1500 mAh pack. The red one is a 9.6 volt pack made from 8 AA NiCad cells. It's capacity in not rated, but it is probably 800 mAh or so. The one in the back is a 9.6 volt Makita power tool pack. The capacity of this pack is not rated either, but I expect that it exceeds 1500 mAh. Packs of these kinds have been used successfully in large scale train use, although two of each would usually be needed. They usually come with chargers that are designed to fast charge them. The Makita packs will recharge in just one hour. The others usually take 3 hours or more.

If you can't find a good source of batteries locally, you can find them for internet or mail order at:

More propaganda on NiMH batteries can be found on the Thomas Distributing WebSite. An overall view of advanced batteries can be found on the Maxim web site.

Based on cost, capability, availability ease of use and ease of installation it looks like that the NiMH technology is probably the best one currently available for dedicated installations. For use in trail cars, the less expensive gel cell technology is probably the best choice. NiCads are often used but I am staying away from them just because of multiple bad experiences with them. I've got a drawer full of dead NiCad computer, camcorder and power tool batteries. Lithium Ion batteries are just too new and are still very expensive.

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Battery Discharge Tests

I ran some tests on a few sample batteries just to see what they would do. The test method was pretty simple. A resistive load was connected to the battery and the voltage and current were metered at intervals during the discharge. After the data was recorded, the area under the discharge current curve was integrated to determine the capacity. Since the load was resistive, the discharge current can be directly calculated from the voltage as a function of time. The value of the discharge current was selected to produce a discharge in about 2 hours, typical of the rate that might be found in train service. The battery was declared discharged when it reached 1 volt for a NiMH or NiCad cell or 5 volts for a 6 volt gel cell battery.

gel cell dataThree Crest gel cells were charged on a Crest gel cell charger and tested. All three appeared to be about the same. The capacity was determined to be 2.7 Ah. As can be seen from the curve, the output voltage decays steadily as the battery discharges. This will result in a slight slowing of a train as the battery discharges. At the end of the discharge cycle, the voltage drops a little more quickly. When a train begins to slow considerably, it should be taken out of service so that the batteries can either be recharged or replaced.

nimh testsNiMH batteries discharge differently than gel cells. After an initial rapid drop in voltage, the discharge voltage stays nearly constant for 50% or more of the discharge cycle and then begins to decay slowly. At the end of the discharge, the voltage collapses rapidly. It will be obvious when the batteries need recharging. These 1300 mAh cells typically demonstrated 1150 mAh of capacity immediately after a fast charge. After being fast charged and then trickle charged for two days, the cell capacity increased to 1400 mAh.

nicad testI sample tested one 1100 mAh NiCad. It has a similar discharge curve to the NiMH cells, but it didn't experience the rapid drop in voltage at the beginning of the discharge. I also didn't get a data point near the 1 volt point. The capacity of this cell was 950 mAh but this battery was not new and had seen some heavy service in a digital camera. This cell was the last survivor of 10 of these cells, all the others had crapped out.

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Rechargeable Battery Issues

The strongest argument in favor of going to a battery/RC system is the presence of the battery. It is also the strongest argument against going to a battery/RC system. Batteries have a serious darkside. They are:

Being heavy is not always a bad thing. The expense is significant, but not a deal breaker. Batteries come in a variety of sizes and people have found room for them in almost any loco. The last two points are the worst ones.

My personal experience with rechargeable batteries of many kinds has been less than stellar. I've replaced rechargeable batteries, sometimes at great expense, in:

I keep a plastic tub in a cabinet just to collect the dead batteries because it is now illegal to throw then in the trash. They have to be treated as toxic waste. Just be aware that whatever battery that you install in a loco will eventually have to come out and be discarded.

The failure mechanisms of rechargeable varies depending on the chemistry, construction and usage, but they will all fail eventually.

Lead Acid. Both the wet and gel cell lead-acid batteries tend to fail in pretty much the same way. After many discharge and recharge cycles, the plate gets converted from lead sulfate back to lead in a more and more disorganized fashion. Lead is converted to lead sulfate during the discharge process and converted back to metallic lead in the recharge process. If the sulfate manages to get dislodged from the electrodes before the battery is recharged, it will pile up in the bottom of the battery and is pretty much lost. The lead sulfate is partially conductive so that if enough collects where it doesn't belong, it will create a leakage path and allow the battery to self discharge or even short out. A battery in the discharged state is the most prone to shedding the lead sulfate so that a battery should not be left discharged for long and should not be vibrated or shocked while discharged.

As the geometry of the plates degrades over time, the battery can hold less and less charge until it finally holds so little charge and leaks enough so that the residual charge is self discharged rapidly enough so that the battery becomes useless.

Overcharging a lead acid cell will cause excess emission of hydrogen and oxygen created from the electrolytic destruction of the water in the cell. This mixture is explosive and, in a sealed cell, can cause cell to burst just from the pressure.

NiCad. There are two major failure mechanisms of NiCad batteries, crystallization and cell reversal. NiCad batteries are also claimed to suffer from "memory" effects, but this effect is difficult to reproduce without continual charging and then discharging to a constant state. Crystallization is also called dendritic shorting. The impact is that crystals grow within a cell and puncture the separator between electrodes and short out the cell. This is generally fatal to the cell. Once dendrites form, then can be dissolved by special charging characteristics, but they tend to reform quickly. A crystallized cell is a dead cell. Cell reversal is caused by a cell degrading and discharging to zero before the rest of the cells in a pack discharge. This causes the voltage across the cell to actually reverse due to current being forced through the internal resistance of the discharged cell. This causes excess oxygen formation in the cell, increased pressure, venting and total failure of the cell.

Overcharging a NiCad cell will cause excessive temperatures in the cell and can result in cell venting and failure among other bad effects.

NiMH. The NiMH cell doesn't appear to suffer from any documented "memory" effect but it still finds ways to die. The NiMH chemistry has the highest self discharge rate of any of the common battery types and this characteristic seems to increase as the battery gets older. They can retain good capacity if used immediately after charging but near their end of life, they can also self discharge in a few days. NiMH cells also suffer from cell reversal in multi-cell packs and don't like to be kept on charge continually even at trickle charge rates of 0.05C or less.

Overcharging an NiMH cell produces similar bad effects as with a NiCad cell.

Lithium batteries. There are several physical structures for Lithium chemistry cells, but all have similar general characteristics. Non rechargeable Lithium cells have a much lower self discharge rate than the other chemistries so that they are highly suitable for low power electronics that have to run for a long time. Rechargeable versions have a lower self discharge rate than the other big three as well, but the self discharge rate of rechargeable Lithium cells is much higher than the non-rechargeable variety. They can also have very high current capability so that they can run power tools and cars. However the batteries have a very limited life cycle no matter how they are made and essentially start to die from the moment that they are made. Depending on the quality and design of the battery, Li chemistry rechargeable batteries will last from 3 to 5 years at best and much less at worst. The primary failure mechanism is restructuring of the reactants inside the battery that happen every charge and discharge cycle. They batteries will last 300 or so cycles before their internal resistance has increased such that the battery reaches half capacity or so. A cell or battery that is over-discharged just once can be permanently damaged so that undervoltage auto-cutoff circuits are desirable integrated directly within the battery (at extra cost).

The end of life characteristic of a Lithium chemistry battery is that one or more cells in a pack will discharge before the others and the internal resistance will increase sharply. Under load, the output voltage will collapse rapidly. The cell that collapses first is usually permanently damaged and then the whole battery is toast.

The charging characteristics of the Lithium chemistry batteries are more critical too. Overcharging just once can cause the battery to fail almost immediately, sometimes with spectacular results. The internet is full of videos of the failure of Lithium chemistry batteries during charging. Lithium is a very reactive metal and it will burn fiercely if ignited by the heat of overcharging or due to some physical damage to the battery that upsets a cell. The heat of overcharging can cause a cell to swell and burst, usually resulting in an intense, but short lived, fire.

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Battery Charging

There are many solutions to the problem of recharging batteries. The solutions can vary greatly depending on the type of battery, the desired recharge rate and the way the batteries were installed.

There are two fundamental ways to charge a battery, fast or trickle. The object of fast charging is to ram charge back in the battery as fast as practical so that the battery can be returned to service quickly. It is possible to fast charge most batteries in an hour or so, but fast charging, even when done with a "smart charger" will take life off the batteries. Expect to wear the batteries out twice as fast due to fast charging if all goes well every time. Fast charge batteries improperly just once and you can kill them off almost immediately. Trickle charging is just that, current is put back into the batteries at a low rate. The method is both safer and less expensive, but it can take a day or two to return a battery to service.

When current is forced back into a discharged rechargeable battery, most of the kinetic energy of the charging current is converted to chemically stored potential energy within the battery. When all of the reactants are consumed, the battery is said to be "charged." When charged, a battery can no longer convert the kinetic energy to potential energy and the kinetic energy is converted to heat instead. If the charge rate is low enough, a trickle charge, the heat build up is shed easily by the battery and not much happens. Most batteries can be left on trickle charge for a long time without damage. If the battery is being fast charged and the charge current is not removed when the battery becomes fully charged, the battery heats excessively. This heating WILL damage the battery. It may get hot enough so that the internal pressure in the sealed battery builds up to the point where it "vents." Venting is a nice term for bursting. This is a bad thing.

maha chargerA good smart charger, like the Maha MH-C204-F in the photo, senses the condition of the battery and terminates fast charging when the battery can't take any more charge. It then converts to a trickle charge to keep the batteries fresh until they are used. This charger detects both "delta V" and cell temperature. With NiCad or NiMH cells, the IV characteristic of a battery changes when it reaches full charge and this change can be electrically detected. The charger adds small pulses of current to the regular charge current and when it detects that the delta V as a result of the pulses goes to zero or slightly negative, it shuts off. If the battery is defective and doesn't respond to the delta V test properly, the charger also detects the battery temperature and shuts down before the battery gets hot enough to vent.

This kind of charger is great for individual cells and if you've got a digital camera, you should get some NiMH batteries and a charger like this. However, if the cells have been built into a pack, they can't use this charger any more. Besides, they are probably bottled up inside a loco and need to be charged as a group. I have yet to find a commercial smart charger that will charge more than 12 volts worth of batteries. A pack of NiMH or NiCad cells built into an engine either needs to be trickle charged, or a custom smart charger can be built with one of the Maxim smart charger integrated circuits.

Lithium Ion cells REQUIRE a very special charger. The charge characteristics of Li+ cells are quite complicated and they CANNOT be trickle charged.

CRE-55494If you are using 6 volt gel cells in a trail car, you can use the Crest CRE-55494 smart charger. It is designed to recharge one to three 6 volt gel cells at a time. It'll recharge the set in about 3 hours and then shutdown automatically to protect the batteries. Each battery is connected to its own terminals on the charger so that they must be removed from a trail car to be recharged. A charged set can then be placed in the trail car and reconnected to allow only a short interruption in operation. Note that this charger runs from 12 to 24 VDC so that you need a DC power pack or a power supply to operate it. It comes with a plug to connect directly to a CRE-55460 Ultima Power Supply.

automotive battery chargerA regular automotive batter charger can be used to recharge gel cells, but with some restrictions. This charger is designed to put out 50 amps for a short period and then a steady charge rate of 10 amps. This much charge current will fry a train sized gel cell battery in short order. This particular one has a 2 amp trickle mode switchable between either 6 or 12 volts. Even in the trickle mode, it'll overcharge a gel cell if it is left on too long. Chargers like this typically cost more than $50.

napa chargerA less expensive option is to use an automotive trickle charger like this one I used on my motorcycle batteries. This 1-1/2 amp charger will charge either a 6 or 12 volt battery at a level that is reasonably safe. It will recharge a typical gel cell in about 2 or 3 hours but it has no automatic shutoff and may damage a gel cell battery if it is left on too long.

trickle chargerA trickle charger that won't damage a battery can be as simple as a power supply and a resistor to limit the charge current. The source can be a DC power supply or an old power pack set to max provided that it has enough output voltage. A good fixed voltage power supply is an old "wall wart" from some broken toy, appliance or computer. I save all of them when I throw a broken device out, the power supplies often come in handy. You want to select the voltage to at least 6 volts above the battery pack voltage and use as large a resistor as you can. The diode is there to prevent the battery from discharging back into the power supply, some power supplies are sensitive to having current driven back into their outputs, especially if they are turned off. With a separate diode and resistor for each battery, this circuit can be used to charge several batteries at the same time provided that the power supply has enough current capability to handle the load.

For a 100 mA charge rate, an 18 volt pack and a 24 volt power supply, the resistor should be about 47 ohms with a 1 or 2 watt dissipation rating. You can monitor the charge current with a series connected current meter, or you can monitor the voltage across the resistor and calculate the current, I=V/R. The charge current will decay during the period of the charge unless the power supply voltage is increased. Since the charge current depends on the difference between the instantaneous battery voltage and the power supply voltage, when the battery is discharged and its voltage is low, it will draw more current. As the battery voltage picks up, the charge current will decrease. Select the resistor and power supply voltage to produce a charge current at the end of the charge at less than 10% of the Amp-hour rating. The charge current at the beginning of the charge will be higher but this is ok because a discharged battery can take higher charge current. The larger the difference between the power supply voltage and the battery, the smaller the current change will be.

Most batteries can be trickle charged at 10% C where C=rated capacity in mAh. A 3 Amp-hour battery can be charged at 300 mA without serious risk of damage. If the efficiency of the recharging process was 100%, you could fully trickle charge a battery in 10 hours at a 10% rate. However, the process in not fully efficient so it will usually take 15 hours or maybe a little less. I prefer to charge at 6 or 7% C and let the process run for 24 hours. It is easy to remember to take a battery off at the same time the next day and if you forget, the current is low enough to avoid the possibility of damage.

Trickle charging can also accommodate cells that have degraded and don't have the same capacity as other cells in the pack. A cell that cannot accept as much charge will start to convert the charge current to heat sooner than the rest. The better cells will continue to accept charge until they are done too.

A pack with a weak or bad cell will display a tell-tale characteristic. It will run fine at first, then the train will slow a bit as the weak cell drops out. The train may run on for quite a while on the rest of the cells until they drop out too. At that point, its time to measure the cell voltage of each cell in the pack to see which are totally flat. These cells can then be replaced.

I don't run my battery R/C locos very often because I find that DCC works for me better overall than R/C battery power. Your milage may differ. Therefore, when I do want to run an R/C loco, the batteries are usually dead or near dead and I currently have only one charging rig. The NiMH ones are usually discharged due to the self discharge characteristic of the NiMH technology. The one gel cell loco, an FA, usually has adequate charge after sitting for several months.

I have one 24 volt laptop computer charger that I bought cheap somewhere. This thing will supply 1 amp and can trickle charge all the locos at once. I initially set it up to charge one loco at a time with one charging plug. I made a charge cable with a diode and resistor in the lead using my "standard" charging connector. This is what is called a coaxial DC connector. I use a 5.5mm x 2.5 mm version, but there are all kinds of them. All my battery locos have this same charge jack so I use the same rig to charge each loco. I set the resistor for the smallest battery, but that limits the charge current for the largest one.

Eventually, I got tired of recharging my locos in a serial fashion so I made a multiple headed cable with 24 volts on each plug. I cracked open each loco open and installed the diode and the correct resistor for that loco inside the loco. The charger runs from switched AC power so it goes off with the layout. Whenever the layout is on, the four locos are getting charged. The diode prevents each loco from sourcing current back out the charge lead and trying to recharge the other locos on the same 24 volt bus when the charger is off.

There are other ways to charge a battery directly from a power supply and get much faster charging but they pose more risk to the battery if not set up and monitored properly. The slow way that I use is gentle on the batteries and doesn't present a hazard if the locos are left on charge indefinitely.

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Equipment Installation Options

There are a number of ways that the batteries, radio gear and other stuff like sound systems can be installed in a loco. The best way will be determined by many factors including the loco type, radio type, desired battery type, operating preferences and cost targets. There is also the issue of a do-it-yourself installation or a professional installation.

One of the most significant decisions that has to be made is where to mount the battery. The result of this decision will more or less direct where the rest of the stuff goes.

Battery Location Impacts
Battery Location Pro Con
Dedicated Batteries in the Loco

Adds weight on the driving wheels which increases traction

Minimizes wiring external to the loco

Allows the greatest operating flexibility

Typically the most difficult installation

Often requires stripping the guts of a loco to make room for the batteries and radio gear

Often requires individually celled batteries to get them to fit

Trail Car

Easiest installation

Minimizes loco modifications required

A single trail car can be shared between several locos

Lots of room for batteries if a box car or gondola is used as a trail car

Discharged battery sets can be relatively easily removed from a trail car and replaced with a charged set

A trail car full of gel cell batteries weighs 5 lbs or more

The weight of the trail car will restrict train lengths on grades

Wheel bearings on the trail car will wear badly unless ball bearings are used

The trail car cannot be cut from the engine


Sometimes the only place big enough to install batteries in a steam engine

If set up properly, discharged battery sets can fairly easily removed and replaced with a charged set

Has all the weight related issues of a trail car

Doesn't help loco traction

Not reasonable to share a tender between several different kinds of engines

Most steam sound systems mount in the tender, can compete with battery installation for space

After the battery location and type is selected, locations for the other stuff must be found.

Each installation will be different so it is not really practical to provide instructions for each of these items. Descriptions of Example Installations can be found at the bottom of this page. From these, you can pick and choose the installation features that apply to you. It is generally desirable to mount everything on the loco frame so that nothing attaches to the shell. This makes testing easier, but it may be impractical on some locos. In that case, try to minimize the wiring between the frame and shell.

There is also the option of professional installation. If you aren't both electrically and mechanically inclined and you can afford it, you might be better off to pay somebody to do the installation for you. The following table lists some of the professional installers that can do the work. Each installer has his preferred receiver, battery and installation type so contact each one of them to find what he can do for you. I have not done any business with any of the individuals or companies listed but each of them has been around for awhile so I assume that they are legitimate businessmen who will stand behind their work.

If you are a professional installer and you are not listed here, its not because I don't like you. I just didn't have the URL to your web site or your email address. I basically created this list from the index of advertisers in a recent Garden Railways magazine.

Professional R/C Installers
Company Types of Radio Gear Installed
NorthWest Remote Control Systems RCS
Remote Control of New England RCS
The Battery Backshop Locolinc
Mike's Backshop Reed's Instant R/C
Electric Model Works Reed's Instant R/C, RCS

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Generic Wiring Options

There are about as many ways to wire battery R/C installations are there are locos that have had it installed. However, they breakdown in to three general categories, the dedicated installation, the trail car installation and the "tri-modal" installation. There are variations and combinations of these themes, but these should be enough to get something going.

Note that many newer locomotives come with some sort of "DCC Compatible" socket arrangement that will accept SOME kinds of receivers in a Plug-and-Play configuration. Also, many newer locos come with one or more printed wiring boards and complicated wiring configurations. There are two schools of thought as to what to do with this stuff. I tend to retain the supplied electronics and work either through or around them. This requires understanding of what is there already and can materially complicate the mechanical portions of the installations as these circuit boards often consume prime real estate needed for the battery and R/C equipment. The other school of thought is to simply rip all of that stuff out and replace it with the radio gear and batteries. This is actually an easier installation option because when you are done cutting and whacking, all you have left is some wires to some readily identifiable loads and more internal room to work with.

simple dedicated installationThis is the electrically simplest of the installations but it may be the most mechanically challenging. The batteries are installed in the loco itself. All the other wiring and accessories have been removed from the diagram for clarity. The battery is supported by a charging jack and protected by a fuse. The power switch is to prevent battery drain while the engine is standing for long periods, is out of use, or to disconnect the motor when the battery is being charged. At it simplest, the R/C receiver has just four connections, two for power and two for the motor. Some receivers are sensitive to input polarity. Be sure to consult your receiver's instructions to determine the correct polarity of the power connection.

Note that there are no power pickups shown in this diagram. For a battery R/C installation, you want to abandon the power pickups. If you leave them connected, the engine may backfeed power to the track and cause problems. Either clip the wires or remove the contact brushes, but remove them somehow.

Also note that each schematic shows a fuse directly in series with the battery. This is important. A short inside the loco not protected with a fuse will almost certainly result in significant wiring and/or battery damage, maybe even a fire.

trail car installationInstallation of batteries in a trail car involves very little modification of the loco itself. If you never intend to run the loco from track power again, then just disconnect the power pickups. If you want to switch back and forth between trail car battery R/C power and regular track power, then install a power pickup cutout switch. Many newer locos have a power pickup cutout switch already installed. Note that some of those switches only cut out one side, which should still be ok, and some of them aren't even wired properly. If your loco has a switch, test it before you rely on it.

The one trail car can be connected behind any loco that has had a power connector added and the contacts disconnected so that you don't have to install all this expensive stuff into every loco.

tri modal wiringThis is a version that I call the "tri-modal" method. It can be done with either trail car or dedicated installations. With the inclusion of two DPDT switches, the engine can run from regular track power, or constant track power with radio control (provided that your RX can accept either polarity of input power) or it can run by radio control from the internal battery. The switches can also be set so that it'll run straight from the battery, but that isn't a very good way to do it. I did an FA this way with internal gel cells, see the link in the examples section below.

With versions of the three schematics shown above, you have seen just about all the ways there are to deal with on board batteries and radio remote control. To connect a sound system, follow the recommendations given by the manufacturers of the radio and sound equipment that you choose.

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Battery Backed Up Track Power

There are ways to run a hybrid track/battery powered system where the battery backs up track power. The main advantage is increased run time. When the engine can find track power, the battery idles. When the track power drops, either due to bad power pickup or running through an unpowered section of track, the battery takes over. There may be some speed decrease while on the battery, but at least the train will keep running. Since the train runs from the track much of the time, a smaller battery will suffice, or the overall run time can be increased. This solution can also avoid problems with reversing loops as the loops can just be left unpowered. The track voltage should be set just high enough to keep the train running from the track.

battery backup schematicThis version is the easiest to implement. The battery and track circuits are steered to the receiver through diodes. Whichever has a higher voltage will supply the current. The battery will still eventually run down, but it will last longer. The battery will then require recharging in the conventional fashion through the charging jack.

If the receiver has its own bridge rectifier and you feel that you can identify the + and - terminals on the internal bridge rectifier then you can wire right into the receiver. You can figure on voiding the manufacturer's warranty if you do it this way.

self chargingAn extension of this approach is to allow charging from the track. Note that the charge rate is NOT intended to be enough to overcome the discharge on the battery and it will still discharge. The advantage is that you can place the loco on a powered track overnight to recharge the battery and avoid the charging jack. The best approach is to assume a fairly high charge voltage like 24 volts and set the charge rate at 7% of the (amp-hour) rating of the battery and charge for 24 hours. Lighting and other loads should be switched off during charging. Several locos at a time can be charged by setting them on the same track. Each will regulate its own charging current.

If you want to get sporty, you can set the resistor to allow charging at a higher rate from your running track voltage. This will result in shorter recharge times at the risk of cooking your batteries if they charge too much. I wouldn't do it this way. This circuit really isn't smart enough to handle that job very well.

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The subject of fusing is so important that it deserves its own section. The fuse is easy to ignore because if you don't install one, everything may still work out ok. However, for safety reasons, you MUST install one. The high tech batteries that we choose to install in locomotives or trail cars can source amazing amounts of current when shorted out. This level of current can ruin an expensive battery in a short second. It can also burn wiring, melt plastic, cause the batteries to burst (resulting in a messy cleanup of toxic materials) or even start fires. Even if your receiver has internal overcurrent protection, that does nothing to help if the fault is in the wiring leading the receiver. Don't mess around. Install a fuse.

fusesThis photo shows two different common kinds. The white object is a typical in-line fuse holder for a 3AG type fast acting fuse which is shown next to the holder. The 3AG type fuse is about the most common type available. You can buy these holders at most any electronics store or Hosfelt (part number 43-172). However they are big. For a trail car installation where there is lots of room and easy access, this is probably the best type. The small black object in the foreground is a 4 amp circuit board fuse. This kind is better for space constrained installations, but it must be soldered during installation or replacement. This type can also be found at Hosfelt (91-204). Similar items are available at Radio Shack.

Another option is to go to your local auto parts store and buy a bag of automotive type blade fuses. Since standalone sockets for blade fuses are hard to find, you can just solder to the blades and then protect the connections with shrink tubing.

Whatever type of fuse that you select, pick a fast acting one. Slow blow types are designed to handle the inrush surge of AC powered equipment as internal capacitors charge up. For train applications, there should be no inrush therefore no need for a slow blow fuse. A fast blow fuse will provide better protection.

There are also solid state fuses available. They have the advantage of automatic reset after they cool down and you don't have to dig into a tight installation to replace a blown regular fuse. The downside is that they are more expensive, harder to find, have higher voltage drop in normal operation and act much more slowly.

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Example Battery Powered R/C Installations

I have only started installing battery power recently so I don't have a long list of example installations. If other's who have published their installations would like them listed here, email me with a URL to your site.

Example Battery Radio Control Installations
Engine Radio Type Battery Type Installation Type Page Author
Aristo FA-1 Crest CRE-55490 Crest ART-55493 gel cells tri-modal FA Tips G. Schreyer
LGB 2060 Crest CRE-55490 1650 mAh NiMH pack tri-modal LGB 2060 Tips G. Schreyer
Lehmann Porter RCS 1300 mAh NiMH cells dedicated with sound Mike's Models Page M. Sheridan
Aristo Center Cab Crest CRE-55491 1600 mAh NiMH cells tri-modal Aristo Center Cab Tips G. Schreyer
Lionel Thomas The Tank Engine Crest CRE-55491 1300 mAh NiCad cells tri-modal Thomas and James Tips G. Schreyer

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What Should You Do?

I normally don't try to suggest to others what they should do. What I think that they should do and what is really the best for them may be very different. However, if you haven't made up your mind up to this point, I'll offer some suggestions.

IF you are running track power now AND it works for you, then there is little reason to do anything. Don't mess with success. Track power is clearly the easiest and cheapest way to go, IF it works at all.

IF track power works for you AND you usually run larger locos or MU consists AND you want to add command control, strongly consider DCC. Larger locos, multiple locos and heavy trains are just too much for batteries unless you run for only short periods of time.

IF you run smaller locos OR single engine trains AND you want to add command control OR track cleaning is a chore OR track power just doesn't work well, then consider on board battery operation with radio control. Smaller locos and shorter trains fall well within the capability of battery power.

IF you haven't laid your track yet AND you don't want to wire it OR you want to spend less money on the track itself, consider battery power from the outset. Larger locos with longer trains may require the use of a trail car to carry enough batteries to get adequate run time but it can work.

IF you are NOT mechanically AND electrically inclined, then you probably should not dig into your locos and tear them up. Either don't do it at all or pay somebody who knows what they are doing to do it for you.

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What Did I Do?

I initially converted four locomotives to battery/RC using two types of Train Engineer receiver and three types of batteries. This all happened in 2001 while I was also experimenting with DCC. At that time DCC for large scale trains hadn't matured enough and it still had problems. However, as time went on, DCC got materially better and I continued to slowly convert more locos to DCC because it was cheaper to do so and with improved boosters and decoders, DCC started working very well. I never converted another loco to battery/RC because in the long run DCC worked better for me. In my particular case, the liabilities of DCC were less than those of battery/RC. Your milage may differ....

By about 2005, a newer crop of DCC decoders became available that worked MUCH better than the older ones. The oldest version of DCC decoders that gave me so much trouble were scrapped and replaced. In 2009, I finished the conversion of all of my regular track powered locos to DCC, both on the outdoor GIRR and the indoor GIRR Mountain Division. I also converted my son's old HO layout to DCC.

I looked back at those four battery/RC locos and realized that they just didn't get much run time anymore. They were literally too much hassle to use. The radio range of the TE receivers was typically limited. Further, the batteries always seemed to be dead, or nearly so, when I pulled one of the locos off the shelf to run it. I don't keep them on charge all the time to prevent cooking the batteries and I never did master the method of determining when I wanted to run one of them a day in advance so that I could charge it up. Since I had wired all but one of them (the 2060) to optionally run from track power, I realized that I could easily rewire them to insert a DCC decoder in the track power path and allow them to run as DCC locos along with the rest of my fleet. Eventually I did that. Each has been converted to add a decoder. The 2060 wiring was modified to make it similar to the others with mode switches. Now, the locos actually get some run time as they are ready to go when I am. The batteries are still there. Some of them are weak because they are old, but the locos still run that way and I can transport them to other layouts. However on the GIRR, the batteries are just ballast.

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© 2001-2009 George Schreyer
Created Feb 18, 2001
Last Updated October 5, 2009