Refurbish a damaged 4S battery - Do not try this!

N5000.4S.35.jpgI purchased a 5000mA Turnigy Nano-Teck 4S 35C, at Hobbyking for my quad-copter in build.

After a small error, i fried out one the "ground side" cell of my battery with 5 or 6 recharge cycles.
So i decided that i dont need right now a 3S battery, so i purchased a 1S Turnigy Battery bundle to repair my damaged one.


So first thing first, remove the damaged cell, was easy with my 80W iron.

3689612292?profile=originalThe new cell, fortunately was almost the same size,just a little wider and shorter.

Is a Turnigy 5000mA 40C


Cheking Battery Health - OK!


All ok, and alight, now is soldering time.


A final Check.


And the final result.

After 30min, and some tape i finally restore the battery, i spend 12€ in the end.
The battery is working, and i know that is not a long life battery, after a over discharge, the renaming 3 cells are stressed, but for a low price and only 2 battery's in my gear that worth the risk.
I have some doubts, the cover is insulator tape, and i dont know how she will do in heat. and the C rate, the original turnigy as 35C and the cell that i brought is 40C .

I hope that you enjoyed my little article.

Good flights!

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  • I use that same Technic, all the cell's had 0,3v differential tops, and i insulated with multiple layers and different directions the metal plates.

    well i will give you a "log" when she burn away.

  • Developer

    I think this is misplaced fear. Don't fly a damaged pack, for sure, but building you own LiPo battery stacks is OK.

    see as an example

    I have been building 3S battery packs from unused LiIon phone batteries. 

    The only danger is that you need to make sure you don't short them or damage the battery causing it to potentially catch fire.

    Its the same as saying, don't work on car, it has flammable petrol in the tank. If you make sure you know what you are doing, it's ok, if you don't, don't ;)

  • Admin


    We understand. Don't worry  about ur blog.  It is just that the opinion of repairing of LiPo stack is not recommended  as the dangers involved are heavy, but some time in situations like yours, you might be tempted to do so  ignoring the dangers. Just try to avoid fixing LiPo.

  • I, i never think that my frist blog entry, was make some rumble, i understand, the warning's, and the negative criticism.

    Im not an electrical engineer, no, but i know a something or two about electricity and battery's, I know the risk's!
    If the moderator want to remove the blog entry i am OK with that, no hurt-fillings, but take the first step how never make something different and unknown.

    Wy i do it? need! Im in Portugal, we need to import all! always with 2 big factors money and time, we can not go to the local radio-stack buy a battery for $20 we need to buy oversees and wait 2 to 6 weak's receive the product and with lucky dont get stuck at customs. Im gadering parts to my project at 9 mouts!

    I what i win with my dangerus invention - a working battery, for now, and i little more understand of the cience of the thing's.

    Just a detail that i learn, it's equally dangerous remove a dead Cell of a battery or add a new one.

    in response to some questions, i did charge the remaining 3 cell's in a normal charge, with 3.9v per cell, without knowing at that time that a cell was damaged, apparently the current pass by it. 

    Im not discharged the battery iet and make a full cycle, but i make a balanced charge and it worked.
    About the storage and use, in metal box far from combustible materials like all my other lithium battery's (like the 18650 type) and how all you should have, an portable fire extinguisher outdoors.

    Regard's, JB.

  • Admin


    Answer that I know for your question is ,

    Good balancer would do the job of first bringing down the voltage difference( cell with higher  v) to  that of other in stack, once at same voltage it starts charging.  Key is  Good LiPo charger with separate balancer port.

    Also , I am told never to store LiPo fully  charged rather 30% charged LiPo has better chance. I have personally experienced puffing of LiPo when fully charged LiPo is stored for long time.  These were in default charge condition for more than two years with no ill effect but after I charged them full and then let it unused for a long period made it puff. This makes me believe that I should not have charged them full and let it lie idle .Other might have different opinion. In any case LiPo is  dangerous if not understood well.


  • I agree with Morli above, so long as the Blog doesn't violate our published gudelines and is not a clear attempt to mislead our subscribers it would be inappropriate to censor it.

    Our comments clearly indicate our disapproval of this dangerous undertaking and our thoughts on why it should not be undertaken.

    The writer was sincere in his attempt and has also pointed out the expected shortcomings.

    In some cases a how to article can really be viewed as a why not to article and that is the case with this one.

    Best Regards,


  • Admin


    Diy Drones  is primarily meant to do things and projects by your self and learn from mistakes  and is for idiots like my self.  This blog is by some one who wants to try some thing which by other standards might be dangerous/wrong. We as Diy Community should not condone such project but at the same time it is Diy  project so should be politely pointed.

    Instead of repairing a 3S with damaged single cell I would have removed/cancelled the damaged one and used it as 2S if I were to do it or being asked for advice. 

    So be polite/friendly to people much below your pay grade or you can join site/group of your own  caliber. DiyDrones is not for " I know it all type guys".


  • Great candidate for Saturday Night Live's - Bad Idea!

  • Admin


    Maybe the comments posted here may serve as a warning, to any member who is contemplating repairing a damaged LiPo, that this is an extremely dangerous undertaking that could cause physical harm or potential property damage.


    TCIII Autonomous Vehicle Developer 

  • Moderator

    Careful, there's still alot of dangerous stored energy in those cells!

    I agree with @John Maffetone, this is not safe and something I would never recommend.

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