Appendix 1. Lipo 101 - athertop/MavLink_FrSkySPort GitHub Wiki

Its important that a LiPo battery is used properly. For example,it is important in principle not to overload a battery!

Overloading can be identified by one of the following:

• Under load, voltage dips resulting in less than 3.3V per cell.
• Under no load, the lowest cell voltage voltage is below 3.6V.
• The capacity of the battery is over utilised. Using more than 80% capacity of a LiPo is not good for its life expectancy.
• The LiPo battery is extremely hot after discharge. The LiPo should not be allowed to be warmer than 60°C under any circumstances. The will damage the internal chemistry!

By being able to monitor multiple readings of the battery during the flight, we can very accurately judge the battery status and so exploit the maximum flight time without threatening the health of the battery.

How our main telemetry screen helps to achieve this:

• First, In flight (ie under load), the cell voltage should never fall below 3.3V. Having Min LiPo cell voltage available on the main telemetry screen allows us to keep track of this. It is also helpful to have audio prompts as the cell voltage changes and the sound of the Critical alarm at 3.3V. With this configured, we always get to hear the alarm if we for example, overload the lipo at full throttle passages. In this case, of course, we need to take care and maybe slow down. Should this happen in the first few minutes of flight, then their may be configuration issues in the model design or perhaps a fulty or old and worn out lipo.
• Second, monitor the power output of the battery. The mAh and Wh readings help us here. All batteries have a specified amount of energy in Wh. And the capacity is measured in mAh. For a LiPo, DO NOT drain more than 80% in order to keep the battery in good health for a longer cycle life. So for example, if we have an 8000 mAh battery, then be sure to not use more than 6400mAh capacity before it is charged again. Or if we stick to the amount of energy in Wh, we should consume only 70,4Wh with a battery rated at 88Wh (it is rare to see LiPos labelled in this regard these days however).
• thirdly, the open circuit voltage of the battery should never be allowed to go under 3.6V. You can verify this by reading the value of the Cell Minumum voltage after the flight. (System Disarmed status).
• fourth, be careful to not overstress a liPo beyond its design current rating (c rating) which will raise its temperature. Over 60° is too hot and can cause serious battery harm! Ensure you have your current calculations correct and select the correct battery for your design.