RC LiPo Batteries: How to Choose, Charge and Care for Them

A LiPo (lithium polymer) battery powers almost every electric RC car, plane, boat and drone made today. It packs a lot of energy into very little weight and delivers high current, which translates into more speed and longer run times than the old NiMH packs. In return, it asks for a little care: charge it properly, never run it completely flat and store it the right way.

How to read a LiPo battery

The label on any LiPo shows three key figures:

• Cells (S). The number of cells in series. Each cell is 3.7 V nominal (4.2 V fully charged). A 2S pack is 7.4 V, a 3S is 11.1 V and a 4S is 14.8 V. Always use the cell count your ESC and motor support: you’ll find it in their specs. If you’re not sure, read up on what an ESC is.
• Capacity (mAh). How much energy it stores. More mAh means more minutes of run time, but also more weight and a bigger pack. Check that the battery fits the tray in your model.
• Discharge rate (C). How much current it can deliver without suffering. Multiply the C rating by the capacity in amps to get the theoretical maximum current: a 5,000 mAh pack at 50C gives 250 A. C ratings are partly marketing, so there’s no need to chase the highest number: it’s enough for it to comfortably exceed what your motor draws.

Also look at the case style: hard-case packs have a rigid shell and are the ones to use in cars, because they handle impacts better. Planes and drones usually run soft packs without a case to save weight.

Connectors

The battery has two connectors:

• Discharge, the thick one that goes to the ESC: Deans/T-plug, XT60, XT90, EC5 and so on. It has to match the one on your ESC, or you’ll need to swap it or use an adapter.
• Balance, the small multi-wire plug, which is only used for charging and for measuring the voltage of each cell.

How to charge a LiPo

1. Use a LiPo-compatible charger with balance charging. If you’re shopping for one, see how to choose a LiPo charger.
2. Select the LiPo program and the correct cell count.
3. Charge at 1C if you don’t know what current to use: 5 A for a 5,000 mAh pack. It’s the safest option and the one that’s kindest to the battery.
4. Never leave a LiPo charging unattended, and charge it on a non-flammable surface or inside a fireproof LiPo bag.
5. Let the battery cool down after a run before you recharge it.

How long does charging take? It depends on the capacity and the charge current: we explain it in how long it takes to charge an RC battery. And if you ever find yourself without a charger, read how to charge an RC battery without a charger first so you know the risks.

If you’re looking for a good starting point, check out balance LiPo chargers on Amazon and a fireproof LiPo battery bag.

Discharge: don’t run it flat

A LiPo shouldn’t drop below about 3.0–3.2 V per cell while you’re running it. Go lower and it loses capacity or becomes useless. That’s why you should:

• Turn on the ESC’s low-voltage cutoff (LVC) in LiPo mode.
• Don’t run until the car stops: when you feel it losing punch, it’s time to swap batteries.
• A per-cell voltage checker tells you the state of each cell in seconds. They’re cheap: look for a LiPo battery checker to keep in your toolbox.

To find out how many minutes you can expect from each charge, read how long an RC car battery lasts.

Storage

If you won’t use the battery for a few days, leave it at storage voltage: about 3.8 V per cell. Most chargers have a “Storage” program that does this automatically. Keep it somewhere cool and dry, inside a fireproof bag or box, and never leave it fully charged or fully empty for weeks.

Signs a LiPo is damaged

• It’s puffed or the case has split open.
• It gets very hot during charging or normal use.
• The cells are badly out of balance and the charger can’t equalize them.
• It has dents, cuts or frayed wires.

In any of these cases, stop using it. Take it to a battery recycling drop-off: don’t throw it in the trash or try to puncture it.

LiPos in planes, boats and motorcycles

Everything above applies just the same to an electric RC plane, an electric RC helicopter, a brushless RC boat or an RC motorcycle. In planes and drones, weight rules, so you pick the lightest battery that gives you the flight time you want; in boats, keep it well protected from water.

This guide is part of our RC electronics section, where you’ll also find motors, ESCs and chargers.

See RC LiPo batteries on Amazon

How long will it last and how long will it take to charge? Work it out with the RC battery run time calculator, the LiPo charge time calculator and the LiPo voltage calculator.