Lithium Polymer (LiPo)

LiPo batteries are a similar technology to laptop batteries. When buying a LiPo pack, there are two things to pay attention to.

The first is the number of cells in the pack. For 1:10 and 1:12 scale racing, it’s usually one or two cells. This is also sometimes called “1S” or “2S”, the “S” referring to how the cells are in series (yeah, okay, “1S” really makes no sense, but I’m not the one making this up, sorry), which adds up the voltage (a LiPo cell is nominally 3.7 volts, so a 2S pack should give out about 7.4 volts). The number of cells is usually dictated by the racing class, so again, check with your local club before buying your packs.

The other is the capacity of the pack, usually rated in milliamps/hours. This number represents how much power you can draw from the pack, in such a way that you’ll run out after exactly an hour. For more entry-level racing, the capacity of the pack simply doesn’t matter that much, because entry-level classes have motors that draw less power, and racing heats last a fixed amount of time, usually short enough that you won’t even come close to run out. Packs with more capacity, though, are heavier, so if you’re racing, you might want to get the lower capacity packs. If you’re just running your car for fun, with no time limit (as in races), you might prefer to just get the bigger pack for a longer run time. Also, if you run motors with fewer turns, or use “boost”, this will use more power, and might want a bigger pack.

LiPo batteries have something of a reputation, as they are liable to catch on fire (!!!) when they overheat. That tends to only happen if they are over-charged (either with too much current, or for too long), if you’re gentle with your batteries, you should be okay. The BRCA recommends using no more than what they call “1C”, which is to say to charge at same amount of current as the amp/hour rating of the battery (which should thus take one hour for a full charge). Remember that 1 amp is 1,000 milliamps, of course! Most batteries are rated in milliamps/hour, and chargers are usually labeled in amps, so if you have a 5,500mAh pack, you’d use 5.5A to charge. Finally, clubs will usually require that you use LiPo bags (which have some fire-proofing), which seems like a good idea, just in case…

In terms of maintenance, LiPos are fairly easy. They don’t like to be completely discharged, but most electronic speed controllers have a low voltage cut-off feature to avoid this from happening. They don’t like to be stored with a full charge either, but since a 5 minute race leaves a pack at about half-charge, that’s easy, you can just leave it as-is after your last race of the day (assuming it was fully charged, which is just a good idea if you’re going into your final race!). You might have to use your charger’s discharge feature if you have an early breakdown, at the worst.

They do not have any “memory effect”, so you can just “top up” your battery between heats, without ill effects. This allows the possibility of racing with a single pack (what I’m doing now, but a second pack might add some convenience).

Nickel-Cadmium (NiCad) and Nickel-Metal Hydride (NiMH)

These are still seen in some ready-to-run (RTR) and used kits, but are definitely on their way out. They require a good deal of maintenance and conditioning to keep operating at peak performance and avoid “memory effect”, are heavier, and of lower power and capacity than the newer LiPo batteries. For anyone getting started nowadays, I would recommend that they avoid them.