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RC Car Batteries
About the 7.2 volt battery
Your rc car or truck uses a 7.2 volt battery pack to power the electric motor, and most cases, the receiver.
The 7.2 volt battery pack is made up of six 1.2 volt sub-c sized batteries soldered in a series configuration (6 x 1.2 volts = 7.2 volts).
There are two physical configurations... the stick pack and the side by side pack. Both are 7.2 volts, except that the side by side pack is slightly wider.
NiCad vs. NiMH rechargeable batteries
There are two popular types of rechargeable batteries, the nickel cadmium (NiCad) and the Nickel Metal Hydride (NiMH).
The NiCad is the old battery technology. It is still good for beginners and playing around. The good thing is that these batteries are now cheap (e.g. $12 USD). The bad news is that these batteries develop memory.
Memory means that these batteries remember their last charge. For example, if you use only 80% of the battery, then recharge it, the battery will only charge to 80% of its maximum capacity. This is not what we want.
To work around this memory effect, racers usually discharge the battery completely, before recharging.
The NiMH is the new battery technology. These are expensive than the NiCad but do not have the memory effect. NiMH also are designed to have more capacity, usually 3000mAH.
Note: Battery capacity is measured in milli ampere hours. For example, an rc car using a 2400mAH battery will run twice as long as a car using a 1200mAH battery.
Tip: Remember, a battery with higher capacity will perform better, but will cost more, and will also weigh more. If you are racing in a stock class, it is sometimes better to use a lower capacity battery that is lighter in weight.
There are timer chargers and peak detection chargers. Timer uses a dial to set how long to charge a battery. This is risky, and overcharging is a common occurrence.
Despite the higher price, peak detection chargers are recommended for beginners. These automatically detect when a battery is fully charged, then stops charging. This prevents batteries being damaged from overcharging.
Note: Be careful, a NiCad peak detection charger is not designed to charge NiMH batteries. Only use NiMH peak detection chargers for NiMH batteries.
Tip: Sometimes peak detection chargers do not "peak" and overcharge a battery. To be safe, stop charging a battery when it becomes very warm to the touch.
Charging - process of restoring energy into the battery.
Discharging - process of removing energy from the batter.
Dump - when a battery suddenly losses all its energy.
Matched pack - batteries that have very similar voltages, amperage, and discharge curve. Used primarily by serious racers.
Memory - negative effect when NiCad batteries are not fully discharged or charged.
Peak - when a battery reaches its peak voltage.
What to do to get the best performance from batteries
Secrets to making your batteries perform better and last longer...
1 Discharge completely before charging.
2 Use a peak detection charger.
3 Charge at a consistent rate, usually 3.5 Amps.
4 Use or cycle the battery (charge, full discharge) at least once a week.
5 Avoid using a battery more than once a day.
6 Avoid charging a warm or hot battery. Let it cool first.
Tips: The higher the charge rate, the higher the voltage and performance, at the sacrifice of lifespan. I usually charge at a 3.5 Amp rate.
What not to do to your batteries
Avoid doing these at all costs...
7 Overcharging. This will permanently destroy a battery pack.
8 Do not let the battery get too hot. This may happen if you are over-geared, using the wrong motor, running the rc car in grass or uphill, or not enough air to cool the battery.
9 Do not "short" the battery. This happens when you accidentally touch the positive (+) end with the negative (-) end.
10 Do not throw batteries in the trash. Dispose of old batteries at a recycling facility.
Batteries for beginners and for serious racers
Beginners and people like me who like to just play around will do best to buy cheap battery packs. For $50 we can buy 4 battery packs and play all day. Any cheap brand will do fine.
For serious racing, there are matched battery packs. These use cells that have been selected among thousands, and are the best. Companies that produce these racing battery packs are Orion, Reedy, and Trinity.
In terms of the battery itself, Panasonic and Sanyo are very popular brands.