Nowadays, LiPo (Lithium Polimer) batteries are used throughout the industry. LiPo’s provide a high amperage / low weight power source. A LiPo battery is a number of (3.7 nominal Volt) cells wired together providing the desired voltage.
The following is an explanation to demystify their designation:
For example a 2200mAh, 6S, 2P, 15C battery pack means that it has:
- 6 LiPo cells wired in Series (giving a total of 3.7 x 6 = 22.2 nominal Volts)
- 2 of these 6S groups are wired in Parallel (giving a total 2 x 1100 mAh = 2200 mAh)
- The capacity to supply up to 2200 milliamperes in an hour (mAh) to a load that draws 2.2 Amps. (1000 milliamperes = 1 Ampere “Amp”).
- The above 2.2Amps per hour discharge rate would then be considered to be 1C (1X it’s Capacity)
- For our example, the battery could provide 2200mAh at a maximum discharge rate of 15C this would then mean 15X2.2Amps = 33Amps.
The nominal voltage refers to a half-full cell. Never use your battery to drain it below 3.3 Volts per cell. Programmable ESC’s (electronic speed controllers) can be set for a soft cutoff at this voltage. A LiPo drained down to 3.0 Volts is considered completely empty & may not be salvageable. The same applies to overcharging, a battery is full when it’s cells reach 4.2 Volts. Past this voltage it may become dangerous and might be a fire hazard.
As a rule of thumb, only charge your battery at a 1C charge rate or less unless the battery manufacturer states that it can be charged at a higher rate.
Charging your LiPo at a lower rate, never fully discharging nor overcharging it will greatly increase it’s lifespan. 300 charge cycles on a good LiPo is not uncommon.
Keeping a fully charged LiPo is okay for a few days. However, beyond a week, gases might build-up inside the cells & damage your battery. Discharge or charge your batteries for storage at a voltage level of 3.7 to 3.85 volts per cell. Computerized chargers have a storage function built-in, charging or discharging you battery cells to the proper storage voltage. Many “Ready To Fly” (RTF) models are supplied with a small rudimentary balancing charger. They are fine but you must remember to manually discharge your battery (by using your model) or charge it until your cell voltage is appropriate.
Never leave you LiPos enclosed in a vehicule on a hot sunny summer day. A LiPo’s temperature should not exceed 160F Keep them warm in winter. If you plan on using your model in a cold winter climate, keep your LiPo at room temperature or slightly higher prior to use.
Please obey the following safety rules when dealing with LiPo batteries:
- Only use chargers designed for LiPo’s. They have built-in safety features to help avoiding problems.
- Always monitor LiPo batteries being charged.
- Keep a fire extinguishing device (extinguisher or sand) nearby in case things go wrong. It doesn’t only happen to others.
- Many people use LiPo charging bags they are designed to contain the flames should a battery be faulty. These bags are inexpensive & can prove to be a life saver.
- If you crash, you battery might be damaged. Remove it from your model, place it in a safe area & observe it for 20 minutes.
- A bulging LiPo is an accident waiting to happen. Like a volcano, hazardous gases & fumes are ready to burst out of your battery. The toxic materials emanating from a LiPo ignite when in contact with air.
- Never puncture a LiPo, it will most certainly catch fire.
- Charge you LiPos in well ventilated areas & on a flame resistant surface.