RC car racing is an amazing hobby. It’s good for your health, it’s very fun, and it can be a great social activity. However, that doesn’t mean that there aren’t quite a few things to research before starting. One of the main things most people seem to get stuck on is the battery in RC cars. There are a few differences between them, and they can be so confusing that some people have even switched to petrol RC cars. That doesn’t mean that batteries are inferior. Batteries can be equally amazing, and they are a bit less convoluted than petrol-operated RC cars to operate.
Basic Types of Batteries
Most people tend to think that there’s only one type of battery for RC cars when that’s not true. Not only that, but different batteries accomplish different things, which is why you should be careful choosing a battery. Most RC cars use some form of a 3 cell battery as a baseline, but some kits might do things differently. In any case, here are the different types of RC car batteries.
If you purchased a ready-to-run model with an included battery, chances are it’s a NiMH. Nickel-metal packs are rugged, inexpensive, and don’t require much in the way of special care. However, they’re heavier than a LiPo battery of similar voltage and capacity (we’ll get to those terms), and their voltage decreases steadily as the pack is discharged. Once you start driving, your car goes slower with each passing minute. Not noticeably at first, but steadily.
NiMH packs are constructed with cylindrical cells, of which there are usually six to eight of them, like those we’ve been dropping into flashlights and TV remotes for years.
LiPo batteries are generally sold as accessories, but there are RTR models that include them. A LiPo battery is lighter than a NiMH of similar voltage and capacity, which helps your model feel more powerful. Also contributing to that “feeling of power” — which is sometimes called a punch by the RC community —is the LiPo’s ability to maintain its voltage longer as the pack is depleted. Instead of delivering less and less voltage throughout your run, a LiPo will hold a steady voltage for most of your run, then fall off quickly at the end of the charge. The downside is typically cost, because LiPos tend to be a bit more expensive than NiMH, but that has significantly changed throughout the years. They also require a bit more care than NiMHs so that they can last for as long and as safely as possible.
The big number on the battery label indicates its capacity in milliamp hours, which is generally shortened to “mAh.” The greater the number of mAh, the longer your car will run per charge, and conversely, the longer it will take to recharge the pack. A bigger number equals a longer run time is all you need to know, but it’s helpful to understand what the mAh rating means. If your battery is rated at 5000mAh, that means it can hold a steady 5-amp load for a full hour. We get “5” from “5000” because a milliamp is 1/1000 of an amp. Divide the mAh rating by 1000, and you get amps. 5000 ÷ 1000 = 5. If you have a 6000mAh battery, it can hold a 6 amp load for an hour. Or, if you put it on a 5 amp load, it will run longer than an hour. All this equates to a longer run time the greater the capacity.
As with capacity, more volts is better, but up to a point. Your vehicle’s power system is designed to handle a certain amount of voltage, and exceeding that voltage will at the very least shut the system down if it has over-voltage protection, or, in the worst-case scenario fry the electronics. The voltage of a battery pack is determined by how many cells it has. A single NiMH cell delivers 1.2 volts, and NiMH batteries are most commonly offered with six or seven cells. These may be referred to as “6-cell” and “7-cell” packs, or they may be referred to by their voltage: 7.2 volts and 8.4 volts. It’s different with LiPos. The principle is the same, but since a single LiPo cell delivers 3.7 volts, LiPo packs have fewer cells for a given voltage. The most common configurations are 2-cell, 7.4-volt packs and 3-cell, 11.1V packs. Depending on your model and how much voltage it can handle, you may even be able to use 4, 5, or 6-cell packs.
As we just discussed, NiMH and LiPo packs are often referred to by the number of cells in the pack: for example, “2-cell” or “3-cell.” You may also see or read about LiPo packs with a designation such as 2S, 3S, 4S, etc. In this case, the “S” refers to series and indicates that the cells within the pack are connected positive to negative. Some LiPo packs feature cells connected both in series and in parallel, which is designated by a “P.” For example, a “2S2P” LiPo pack would have two pairs of LiPo cells inside. Each pair would be wired in parallel (2P), and the two pairs would be wired together in series (2S). Nearly every RC LiPo is wired in series and simply referred to as 2S, 3S, 4S, so it’s not something you should be worrying about, but it’s important to note.
First and foremost, it’s important to get a NiMH charger if you have NiMH batteries, and a LiPo charger if you have LiPo batteries. If you use both types of batteries, some chargers can be set for either battery type. If you go that route, be sure to set the charger for the correct battery type before you hit the “start” button. As for charger features to look for, the most important is amperage. The higher the charger’s amp output, the faster it can charge your pack. If your car or truck came with a generic charger, you’ll notice its label shows its output in milliamps, for example, 300mA. If you had a 300mAh battery, that charger would juice it up in an hour. But chances are you have a 3000mAh (or higher) pack, and that means you’re looking at 10 hours of charging before you get to play again. If you have a 4-amp charger, that 3000mAh battery will be charged in about 45 minutes.