These day’s lipo batteries are increasingly expensive, so pilots are becoming more and more concerned with saving batteries, particularly when they are over discharged or miss-treated.
Below is a guide to saving an over discharged lipo and it can also be applied to a lipo with a dead cell.
- Carry out a visual inspection of the outside of the battery to ensure there is not significant puffing, strange dimples or any other deformities
- Look for damages or anything that looks suspicious – ultimately replacing a lipo is better than replacing a house!!!
- While recharging ensure permanent visual range is maintained with the usual lipo Safety precautions of sand etc.
- Mark the battery so that once recharged and flying again you know to look out for any odd characteristics such as one cell discharging faster than others etc
The problem and why it is hard to recharge over discharged lipos
The issue lies in that many lipo chargers refused Over-discharged LiPo , particularly when their cell voltages drop below 3V. When one is flying without a battery buzzer, telemetry, timers or other battery warning mechanisms it can be extremely easy to get caught up in the chase and other discharge lipo batteries.
As Manufacturers become more and more aware of the dangers of lipos, they implement more and more safety protocols into their products. In the case of lipo chargers many of them refuse to recharge over discharged lipo batteries because the cells become more unstable once over discharged.
- Put your lipo charger onto NiMh mode – these typically have lower battery voltages then lipo’s so they will charge a cell below 3V
- Charge the lipo very slowly and very carefully – most chargers allow the lowest possible current, e.g. 0.1A.
- Make sure to set the charge voltage to the closest nominal voltage of your LiPo pack. (i.e. 7.2v for 2S 7.4v pack, or 12v for 3S 11.1v pack).
- It should took 2 minutes or so to bring the cells back to 3.0V.
- Once 3V has been reached unplug your battery
- Change to LiPo mode on the charger and do a carful balance charge into ensure the safe recovery of the battery
Using this method makes it easy to recover over discharged batteries, however, we at Drone Insider do not recommend making a habit of this procedure. Constantly over discharging LiPo battier will cause their life span to drop significantly over time. Furthermore, it increases the likelihood of fires while charging and unstable cells.
However, carrying out this procedure for once or twice for a battery won’t do much harm.
Hope this helped. If you have any other tips and tricks comment below.