The power side of your nitro car
This article was originally published in RC Driver’s August 2016 issue.
This month’s electric column is a little different. We’ll talk about the electric side of nitro cars. In the past there were only two options for batteries to power your racing machine’s electronics; hump pack or straight pack; a four-cell dry-cell holder is never an option for a racer. If you want to go way back, NiCds were once the only way to go, but they have been nonexistent for some time. NiMH cells have taken over for NiCd cells as they are much friendlier to the environment. Over the years we have seen companies making LiPo and LiFe packs that fit into the same area as the five-cell NiMH packs. LiFe and LiPo each have their advantages; so how do you decide which is the best for your application? Let’s look into the pros and cons of each of the three and give you the best options to satisfy your needs.
COST: $30 to $50
VOLTAGE SUPPLIED: 7.4V
LiPo packs have been around for years and are generally configured to fit in place of the hump or straight style NiMH packs. These packs are 7.4V and arranged in two-cell configurations but if used with regular 6.0 volt systems they will need a voltage regulator to cut down voltage. If you go this route you will need to figure out how many amps your system draws and purchase the correct amperage regulator to suit your needs. On the other hand, most radio companies offer high voltage servos and receivers suited to take advantage of the 7.4 volts. These, however, come at a higher cost than the regular 6.0 volt stuff. The LiPo packs offer a considerable weight savings since they are close to half the weight of the NiMH packs and have a capacity of 30% more than a NiMh pack of the same rating. So this means a LiPo pack of 2000 mAh rating actually has a true rating of 2600 mAh. This happens because a Li-Poly pack delivers a linear power supply which is more efficient than a NiMh pack. A LiPo requires a LiPo specific charger with balance port so the battery can be properly maintained.
Linear power distribution, powers modern high voltage servos.
A hair more expensive, requires higher priced LiPo charger, requires a voltage regulator if used with 6.0V equipment.
COST: $15 to $30
VOLTAGE SUPPLIED: 6.0V
The NiMH battery pack has been around since they replaced the NiCd packs which were phased out quite a few years ago. They are either assembled in hump style with two cells on top and three on the bottom or five cells in a row to make a flat pack. They offer 6.0 volts and a capacity of up to 3000mAh. These packs are heavier than their counterparts which could be an issue if you’re looking to save weight. NiCd packs are suited for standard 6.0V servos and receivers. PROS—Works with all receiver/servo combos, low cost, only requires a NiMH-specific charger which can be found inexpensively. CONS—If left idle for extended time periods — usually two weeks or more— can lose some of their charge.
AVERAGE COST: $30 to $50
VOLTAGE SUPPLIED: 6.6V
LiFe packs are all over the market and offer a nominal 6.6 volts of power with a capacity range up to 2500 mAh. They are also arranged like a LiPo pack in two-cell configuration and weigh the same. These packs are built to fit hump or straight pack spaces. The biggest draw to these packs is the life span; up to four times the life span of a LiPo, and they can be used with most 6.0 volt servo/receiver setups. But just in case, I would check with the manufacturer of your system to see if they can handle the slightly increased voltage. These packs require a LiFe specific charger with balance port.
Can be used with most electronic equipment, long life, safe to use, lightweight.
Requires higher priced LiFe specific charger.
With the three choices and the information provided, figuring out what will work best for you should be a little easier. Before you make a random purchase, take your time and make sure your radio systems can handle the voltage of the type of pack you want. Preset a price range you can afford, too. Take into account what the total cost will be for the charger and the battery and regulator if needed.