What4Electric

What Do I Need for Electric Cars?

The Radio
Most radio systems for R/C cars and trucks are simple, 2- channel units that are much less expensive than those used for aircraft. They will usually not come with rechargeable batteries so it will be necessary to purchase 8 alkaline cells to power the transmitter. Most systems today are equipped with a Battery Eliminator Circuit (BEC) in the receiver so that the radio in the vehicle can be powered by the motor's battery pack. Rechargeable NiCads may also be used for the transmitter and are available separately.

The Battery Pack
A rechargeable battery pack is required to run virtually all electric cars and trucks. These are typically made up of 6 or 7 NiCad cells wired together in a pack which is removable for charging. Most racers will have several battery packs, running with one while another is charging. Charge times are usually about 20 minutes.

Matched Battery Packs
Matched battery packs are also available and these give you the most power right till the end of the pack's discharge. All NiCad cells are not created equal and some will have more capacity than others. A six cell pack, made up of six different NiCad cells, will only give good power while all six are delivering their best. If one cell drops off first, the pack will have lost its oomph and that could be critical in a race (not so serious for sport running). In other words, a pack is as good as its weakest cell! A matched pack is assembled from cells that have been tested for capacity, all cells being more or less equal, delivering the same power.

The Charger
There are various types of chargers available for R/C car packs and these are powered from either 240 VAC or 12 VDC or both. Overnight chargers are inexpensive and give a good charge, equalizing the cells in the pack (every pack should be slow charged at an overnight rate every four to six charges). However, they are slow, taking 10 to 15 hours for a complete charge. This makes them impractical for use at the track unless you have a lot of packs charged and ready to go.

Most beginners to the sport will get a timed charger that will operate from both wall current and a 12V car battery. That way you can charge from home or at the track from a car if no AC is available. After the battery is connected, a discharge circuit is turned on discharge the pack completely. This ensures that all cells are in the same charge state and that you will not overcharge the pack. After discharging, a timer is turned on and the pack charges for as long as the timer is set. Most chargers will take between 15 and 25 minutes to charge a 1400maH pack. These chargers usually also have a trickle charge mode where the pack may be charged at the overnight rate.

Another popular charger, used by most competitors and advanced racers, is the "peak detection charger". These units have electronic circuitry which can detect when a battery has had a full charge. You can plug the battery in, turn on the charge circuit, and leave it until the unit kicks back to the trickle charge rate. These also take approximately 15 to 25 minutes to charge.

The Motor
Electric Motors for R/C cars and trucks are almost all of the "Mabuchi 540" design with a wide range of different kinds of winds and number of winds of the armature. The different winds give a different compromise between speed and torque. They are broken down into two main classes, stock and modified.

Stock motors must be run as is and cannot be opened for modifications. Modified motors can have their timing changed (position of the magnets with respect to the armature) or whatever modifications the driver wishes to make. Modified motors generally have more power than stock motors but will drain the battery pack faster. Be careful when installing a modified motor in a vehicle meant for a stock one. The gears and the speed control may not be able to handle the extra demands of the greater torque and higher current.

Speed Controls
There are two basic kinds of speed controls used in R/C vehicles, the mechanical kind and the electronic kind. Many of the kits (but not all) will come with a mechanical unit. These are generally three speed forward, three speed reverse and are less expensive than the electronic ones. Electronic Speed Controls are far superior to the mechanical ones as they give precision control of the current going to your motor, fully proportional from stop to full speed. They almost always have brakes and may or may not have reverse. Some electronic speed controls are available with radio systems as a substitute for one of the servos.