Rescue Over-Discharged Lipo Battery

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 an empty-charged battery using instructions in this article, you do so at your own risk. Remember the longer you leave the battery over-discharged, the worse performance it becomes as internal resistance would start going up.

So when this accident happened, the voltage of the over-discharged LiPo battery was measured at a total 1.9V (that’s 0.63V per cell). My charger couldn’t recognize the battery and I thought it might be damaged permanently. But then a friend told me that 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 (above 3V per cell) by charging it up using a Ni-MH charger, your Lipo charger might recognize it again. So that was what I did, if you decided to give it a try, do it extremely carefully and do it at your own risk, I won’t be held responsible if you burn your house down. :D


Steps:

  1. So first of all, you will need a NiMH capable charger. A lot of LiPo chargers can charge NiMH too, like the Turnigy Accucel 6 I had at the time.
  2. I connected the main plug of my battery to the 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).
  3.  It should only take a few mins to bring the cell voltage back to 3.0V. I recommend to stop the charging as soon as the voltage reach around 3V-3.3V.

After these steps, I then tested it with my LiPo charger, and it finally recognized the recovered battery. I used the Lipo balance charging feature to charge up the Lipo battery to full capacity, and it 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 whenever possible, and remember to switch off / disconnect your equipment when not in use.

Read about the basics of LiPo battery in this guide.

Edit History

  • Dec 2013 – Article created
  • May 2017 – Article revised

12 thoughts on “Rescue Over-Discharged Lipo Battery

  1. Mario

    You should add a disclaimer at the top that this only aplies to recently discharged lipos, within a few hours.

    Once the lipo discharges the chemicals in the battery start creating byproducts that cuase the internal resistance to go up fast. You should have a multimeter to check resistance frequently in the battery before, during and after trying to revive it.

    Reply
  2. Eugen

    Great! Thank you. It worked for me too. I used ~ 1/10 C current and leave it for ~1 minute. It brought my “dead” cell from 1.9 V to 3.2V. And now i can charge it with the normal LiPo program. Great! Thanks again.

    Reply
    1. Eugen

      Now, a few month after i did the “revive” on my battery, i used it one and then i charged it for storage. All looked good at that time. Today, when in borugh the LIPO pack to use it , found that the “dead” cell is dead again at 0.6V. Thus, it looks the dead cell is not truly revived and is just a momentary solution. And by the way, this battery performed way poorer than another good one.

      Reply
  3. Adam

    Hi Oscar,

    I also use a Turnigy Accucel 6. I am curious how you charge multiple batteries with it. I am flying now with 3S 1300mAh batteries and charging them one by one can take a lot of time (not to mention I don’t leave them unattended, they are always in eyeshot when charging). I have seen parallel balance boards — is this something that would benefit me? It looks like the charger can pump out enough amps to charge more than one at a time (I am charging 1300mAh at 1.3A) but I am not sure how to safely hook them up and determine the charging voltage (1.3A x number of batteries?)

    Any help you can provide would be greatly appreciated. I absolutely love your blog, you cover the big stuff as well as the little stuff I run into like broken balance plugs, etc. You are a tremendous resource for RC flight information on the Internet. I just wanted to say you are very much appreciated for what you’re doing.

    Reply
    1. Oscar Post author

      Hi Adam, thanks for the kind words!

      I use a parallel charging board, and I wrote something on Parallel charging before:
      Parallel charging Guide

      I recommend getting a board that comes with fuses for extra safety!
      for example like this one.

      regards, Oscar

      Reply
  4. PilotPatch

    Oscar,
    Great blog, has helped me with so many things to do with multi rotors. I have done this twice with my tx battery (i know stupid!) and now the cells are unbalanced and one cell won’t hold charge. Does this mean the lipo is at risk of fire? I have had previous fire with lipo charging and nearly burned the house down! Just want to be sure now with this unbalanced lipo or should i just replace? btw keep up the good work.

    Reply
    1. Oscar Post author

      Hi PilotPatch, all over-charged Lipo are not safe, not to mention to you over charged it twice! My advice is to replace it, and dispose the old lipo safely :)

      Reply
  5. Federico

    I agree with you, if you apply a constant current charge (I think 1/5 C is good) you will recovery your battery or know if is dead. For a demostration of own (built from scratch) hexacopter we left in the stand of a contest, I went to the stand (after a inauguration of the contest) and the lipo was dead (and very inflated), I wait three days to deflate the lipo and chargue manually, I need to test the performace of the Lipo (4S 3.7 Ah) to check if the lipo has the required characteristics to maintain our UAV in the air, I think I build a circuit to do that.

    Reply
    1. Oscar Post author

      What I found was, once the lipo has been over-discharged, the cells tend to be unbalanced, even “balance charging” cannot fix this. Happens to me a few times now, although these Lipos are still usable, but the flight time is somehow shortened…

      good luck with your DIY circuit!

      Reply

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