Frequently Asked Questions - Batteries

Electric Radio Controlled cars are powered by a battery pack made up of 6 cells connected together.

Any battery pack will provide the motive power, but for speed and endurance (to last the race) the cells need to be well matched, and in good condition.

Battery power depends on -

How well matched the individual cells are

The efficiency of the connection between each cell

The efficiency of the connection between the pack and the motor

How well the cells are charged/discharged

It is very important therefore, to buy the best cells and to maintain them well.

For more information, 'click' on the links in the list above.

Matched battery packs.
Battery cells are not identical. The amount of power which a cell will hold, and the rate at which the power will be released can vary considerably.
However, it is possible to record and compare these characteristics so that a 'matched' pack can be created in which the cells are similar. This increase the performance, and the useful 'life' of the cells.
The more expensive sets have cells which are very similar.

The efficiency of the connection between each cell
Ready-made 'stick' packs are assembled by the manufacturer and should have no connection problems.
'Saddle' packs are assembled by soldering connecting plates and/or wires to single cells so that the pack fits the space in the chassis.
Therefore, the efficiency of the pack depends of the standard of soldering - and each solder joint could be faulty.

The efficiency of the connection between the pack and the motor
Ready-made 'stick' cell packs are often fitted with a 'Tamiya' connector.
The connector is easy to use and is designed so that it is almost impossible to connect the wires the wrong way (e.g. red to black).
BUT the contact area for the electrical connections is quite small, and can become loose or distorted with use. This increases the resistance and reduces the flow of electric power.
The physical connection remains strong, so the problem is not obvious. Regular inspection is essential.

A popular alternative connector is the 'Corallie' type, a 'bullet' connector with a large contact area inside a matching tube. A very firm 'fit' is achieved - which aids the flow of electric power.These are often found on self assembly saddle packs.

How well the cells are charged/discharged
The method of charging/discharging depends on the type of cell.

Nickel-Cadmium (Ni-Cad) cells

....should be fully discharged after every use
....should be stored fully discharged.
....should be charged with a charger which includes a peak detection device - to automatically stop charging when the cells are fully charged.

'Saddle packs' have their cell ends exposed and each cell can be discharged independently. This means that the pack is completely discharged and a fresh charge will be applied to an empty cell - memory is not a problem.

Nickel Metal-Hydride (NMH) cells

....should not be fully discharged after use
....should be stored partially charged
....should be charged with a charger which includes a peak voltage detection device - to automatically stop charging when the cells reach their optimum voltage.

Battery Power
Two distinct types of battery are available and in regular use for RC racing.

Ni-Cad (Nickel-Cadmium) have a range of different power outputs from 1400mah (milli-amp hours) to 2400mah and are the 'traditional' rechargeable battery.

NMH (Nickel-Metal Hydride) have a higher power output of 3000mah. They are designed to last longer, but have slightly less 'punch'.
To put this battery power into perspective. If a 3,000mah cell pack is connected to a component that uses 1 amp, it will last for 3 hours. If the component uses 3 amps, the cell pack will last for one hour.
Under race conditions, the same battery pack will last for between 7 and 10 minutes!

This discharge rate can only be achieved if the individual battery cells operate in exactly the same way, discharging at the same rate, and for approximately the same amount of time. The manufacturing process does not produce 'clones' however, so each cell is carefully tested and combined with others with the same operating pattern. The cells which are most closely matched tend to be more expensive.