We were out flying on New Years and Big B sent his shiny new Super Sky Surfer into the top of a particularly gnarly walnut tree. We got it down last weekend, but after a week the LiPo in it was stone dead. His charger threw a Low Voltage alarm and wouldn't charge it.
Normally we charge these in LiPo Balance mode. This won't work with a dead battery. The trick is to slowly charge the battery at a low level to get it where the LiPo balance will work. To do this I...
- Place the battery in a fire resistant container, just in case.
- Place the Battery charger in constant current (NiMH) Charging mode.
- Set the current limit to 0.1 Amp.
- Start charging:
- Watch for any sign of battery failure.
- Do not leave the charging battery unattended.
- Charge the pack until it reaches a voltage that is acceptable to the balance charger.
- I used 10 volts, i.e. 3.3 volts times the number of cells.
- 1s = 3.3 volts
- 2s = 6.6 volts
- 3s = 9.9 volts
- 4s = 13.2 volts
- Ns = N * 3.3 volts, where N is the number of cells.
- Stop charging.
- Check to make sure the battery is not hot. If it is, let it cool.
- Switch the charger to Li-Po Balance Charge:
- I don't want a fire on my desk, so I limited the Balance charge to 0.1 Amp to prevent overheating.
- Start Balance Charging.
- Do not leave the charging battery unattended
- The charger should stop automatically.
This worked for me; I hope it works for you.
Hat tip to Youtube user NOTEB00KPC for this idea!