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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  • 100KM

    Jorge, appreciate the time spent to post this - I think this is a useful post and should be encouraged. This whole site is called DIY drones (emphasis on the DIY part). As other posters observed the objective of this site is to help members create autonomous flying vehicles with large spinning blades all over them. Much more dangerous then a rebuilt battery.

    Most of the danger here is during the rebuild where a short could cause problems. If someone shorts a LiPo they are going to know about it (sparks etc) and will certainly have plenty of time to move away before anything goes seriously wrong.

    Once the rebuild is complete and the pack balance charged the danger is no different to a normal LiPo - over discharging/charging/shorting etc could lead to problems.

  • I thought this was DIY Drones, not Buynewandneverfixanything Drones!

    I have replaced a cell before, its quite simple if you are confident with an iron and basic electronics! Less politics more diy like this please!

    Ps, always make sure your fire extinguishers are in date and the correct type
    • ... but please don't post lessons in how to commit suicide on these forums (which are so incompetently moderated that things like this are allowed to see the light of day).
    • ...That's not how it works, Coyle. This thing needs to be removed. Newbies will see the nice detailed pictures of this insane technique and will not heed the warnings (warnings after all are all over every last thing these days).

    Some serious control freakiness here, if not plain “I know better, others won’t”.   Reminds me of “don’t post this”  advocates when grey or black hat hackers find security vulnerabilities. Security through obscurity? I don’t think so. Doesn’t even work anyways.

    Kudos to the moderator (s?) for disregarding this plea. There are hundreds of ways to blow up Lipos inadvertently, and in general millions of ways in everyday life to cause life threatening damage messing with man-made, or natural, things. Reporting on  repair experimentation with clear warning is a good thing. More knowledge, better risk assessment.

    Thanks for the great post.

  • Moderator

    I think this is an interesting and informative post.  The author did a good job explaining the potential hazards.

    Good job, Jorge!

  • I can't see a problem with the posting.  A little while ago everybody was complaining that that DIY drones is getting too political and there were no build posts.  A guy posts a DIY project and gets jumped on - go figure.

    Yes it probably not a good idea to routinely rebuild packs however sometimes in an otherwise perfectly OK battery one cell fails and with balance chargers it cannot be charged due to too much cell imbalance or too low voltage.  If that is a 6S then you are throwing out 5 perfectly good cells.

    I can see it is probably safer just to take the offending cell off and make it a 5S however if you really need the 6S and do not have the money for a new pack then using this technique and being really careful you could be back in the air with a 6S that will work fine.

    I think the author also explained the dangers and limitations pretty well.

    If we want more DIY posts here how about we don't jump all over them when they are posted......


  • T3
    Thanks for sharing. It's not something I would try or recommend. I've destroyed a number of batteries doing stupid things. Basically overloading or shorting them out. To those that read these post, please take extreme care when working with lipos. They can catch fire or blow up. Never charge them unattended.
  • Developer

    I am much more worried about the spinning knifes we fly around for fun..

  • I agree that some (a small percentage) of the members here can be expected to undertake this with adequate fore-knowledge and safety precautions in place.

    For the remaining 90% + of us though this is a precarious undertaking, Lithium Poly batteries contain Lithium which is toxic and flammable and can't even be put out with water.

    Worse with a significant state of charge our Flimsy little plastic film encapsulated LiPos can be viewed as a miniature fuel air munitions device, ready to go off at the slightest provocation (or Short Circuit).

    This is kind of like cutting Estes rocket motors in half to remove the parachute ejection charge - generally - a Bad Idea!

    It is at least very important to emphasize that messing around with this single component is far more hazardous than any other component.

    At the very least you need to be meticulously careful and cautious when "splicing" damaged LiPos.

    I've worked directly with Lithium, Potassium, Sodium, Beryllium and every concentrated acid and alkali and toxic organic you can name including HF and red fuming nitric acid.

    Without extreme care in following laboratory safety procedures, there would be less of me than there is now.

    Lithium batteries represent a very significant hazard.



  • Admin


    I think Theo's "incompetently" statement was in reference to the Forum moderation and not the content of the blog post:-)

    If I may summarize here: Building or rebuilding a LiPo is not inherently dangerous as long as common sense safety precautions (ie: do not short the cells during the build/rebuild) are followed and is possibly conducted under the guidance of an experienced member with battery rebuilding experience.


    TCIII Admin  

  • I'm with Bill.  I am not seeing what the big deal is here.  Theo says this was done "incompetently", so exactly which details has he done wrong?  How would it be done better?

    I have also rebuilt packs.  This is not, in fact, rocket science.

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