Over-discharged LiPo batteries sometimes cannot be recognized by LiPo chargers when their cell voltages drop below 3V. In this incidence, I accidentally over-discharged my LiPo battery in my radio transmitter by forgetting to turn it off. In this article I will show you how I fixed it.
If you attempt to rescue a empty-charged battery using instructions in this article, you do so at your own risk. Also the longer you leave the battery discharged, the worse performance it becomes as internal resistance would start going up.
I measured the voltage of the over-discharged LiPo battery, it was at 1.9V in total (that’s 0.63V per cell). My charger couldn’t recognize the battery and I thought it might be damaged permanently.
But then I read on the internet and there could be a fix to my problem.
My understanding is, as soon as we increase the voltage in each cell to a higher level (around 3V) by charging it up using a Ni-MH charger, your Lipo charger might recognize it again. So this is what I did, if you decided to give it a try, do it very carefully and do it at your own risk, I won’t be held responsible if you burn your house down.
So you will need a NiMH charger.
Luckily my Turnigy Accucel 6 LiPo charger is also capable of charging Ni-MH batteries. I connected the main plug of my battery to the NiMH charger, and charge the Lipo with the lowest possible current, e.g. 0.1A. If you have to also set the charging voltage (I didn’t have to in my case), set it to the closest voltage to the nominal voltage of your LiPo pack. (i.e. 7.2v for 2S 7.4v pack, or 12v for 3S 11.1v pack). It only took 2 mins to bring the cell voltage back to 3.0V. I recommend to stop the NiMH charging when voltage reach around 3V-3.3V.
I then tested it with my LiPo charger, it finally recognized the recovered battery. I used the Lipo balance charging feature to charge up the Lipo battery to full capacity, and all seemed to work.
Although we can save over-charged batteries this way, over-discharging is not good for the battery life! So remember not to over-discharge your battery, and remember to switch off your transmitters and disconnect all devices when not in use.
Read about the basics of LiPo battery in this guide.
- Dec 2013 – Article created
- May 2017 – Article revised