I have ruined a 3S LiPo 5400 mAh and I am unable to understand the reason. This is directly related to my earlier question which was about same battery.
I bought a new balance charger and put the battery on Balance charge on 3.5 Amps. When the battery was fully charged I checked its voltage with a Uni-T voltmeter and each cell was showing 4.3V when the charger was showing 4.2.
Battery was not hot, its temperature was being report as 25C and it did not puff at all.
I always try to take all the necessary precautions, and when I noticed that the battery is over-voltaged I immediately put it under some load (1/4th of normal) to drain the battery and reduce the voltage.
After some time it was within reasonable limits. This supposed overcharge remained for about 20 minutes.
Long story short, when i recharged the battery with another charger and then put the battery to use all the capacity was gone. 25 Minutes flight time was reduced to 5 minutes all in one day.
The internal resistance of cells as being reported by 2 chargers is not too high. 9mΩ 6mΩ and 5mΩ
I am wondering what happened? Is one time overcharge enough to ruin a perfectly normal battery? I know the battery is gone, but i want to learn from this so i can use the future ones better.
Everyone on internet keeps talking about low voltage but not really over voltage packs so i'm asking here.
This battery Never went under-voltage. Under load the cells at worst went to 3.6V
When I recharge the battery it reaches 12.6 Fine, and the charger reports as having provided 2700 mAh to it after starting at 11.1 V
What happened? Is the cause Lithium Plating? I want to learn lessons from this.
The numbers supposedly make sense, but the sudden discharge doesn't. As soon as you put the battery under load it instantly drops Voltage. on 1/3rd of the standard load it behaves like a perfectly fine battery.
The only other variable is that the temperatures have dropped recently due to winters. Now outdoor temperature is 11C and on last good flight it was around 25C