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Battery Powered Radio Control Tips
Contents
- Why Run Trains On Battery Power?
- Train Control Methods
- Why Use Command Control?
- Comparison of Battery R/C and DCC
- On Board Radio Gear Selection
- Rechargeable Battery Selection
- Battery Discharge Tests
- Battery Charging
- Equipment Installation Options
- Generic Wiring Options
- Example Battery Powered R/C Installations
- What Should You Do?
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. In some environments, 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.
Adding radio control to a battery power system adds the capability of command control, a highly desirable feature. However, adding Digital Command Control (DCC) to an existing track powered system does the same thing, 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.
| Characteristic | DCC | Battery R/C | |
|---|---|---|---|
| Track Wiring and Continuity | Pro |
Needs only one track connection |
Not needed at all |
| Con |
Needs some wiring Needs good rail joints |
None |
|
| 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 |
| Con |
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 |
| Con |
None |
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 |
| Con |
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) |
| Con |
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 |
None |
| Con |
None |
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 |
None |
None |
| Con |
Operators have to pay attention |
Same |
|
| 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 |
| Con |
Needs special boosters or autoreversing modules and extra power feeds to accommodate reversing structures |
None |
|
| 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 |
| Con |
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 |
| Con |
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 |
| Con |
None |
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 |
| Con |
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 |
None |
|
| 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 |
| Con |
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 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.
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 four systems listed above, I have extensively used only one of them, the Aristo Train Engineer. Since I don't have experience with the other three, 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:
- Sealed lead acid (gel cell)
- Nickel Cadmium (NiCad)
- Nickel Metal Hydride (NiMH)
- Lithium Ion (Li+)
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.
| Characteristic | Gel Cell | NiCad | NiMH | Lithium Ion |
|---|---|---|---|---|
| Energy Density by Weight |
Low |
Moderate |
High |
Very High Cells are lighter than other types for the same volume |
| Energy Density by Volume |
Low |
Moderate |
High |
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 |
Low |
Very Low |
Moderate |
Moderate |
| 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 |
TBD |
| 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 |
TBD |
| 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 |
Variable 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 |
Good Less than 10% capacity loss per month |
| Cost |
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 |
High $10 per cell or more hard to find in bare cell configurations |
This 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.
This 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 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.
Three 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 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.
I 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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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.
A 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 that can only charge one cell at a time. The charge characteristics of Li+ cells are quite complicated and they CANNOT be trickle charged.
If 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.
A 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.
A 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.
A 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. You want to set 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.
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. 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.
There are other ways to charge a battery from a power supply, but they pose more risk to the battery if not set up and monitored properly.
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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 | 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 |
| Tender |
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.
- Radio receiver
- Antenna
- Power switch to disconnect the batteries when not in use
- Charging jack (unless trail car batteries are physically removed for charging)
- Fuse (important to protect batteries and wiring)
- Sound system (if used)
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.
| 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.
This 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.
Installation 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.
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.
This 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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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.
| 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 |
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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.
This page has been accessed times since 18 Feb 01.
© 2001-2002 George Schreyer
Created Feb 18, 2000
Last Updated May 11, 2002
