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How To repair a lipo

Discussion in 'Electronics and Electrical' started by sinistercad, Nov 14, 2011.

  1. sinistercad

    sinistercad Registered

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    Ok guys first off I'm going to say that if you try anything I have listed and hurt yourself, your dog, your wife, etc. etc or anything for that matter I AM NOT RESPONSIBLE.  With that out of the way lets get to it.

    Here we have a hard case 4500mah 2S 7.4 volt lipo that has lost continuity in the pack.
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    First you need to remove the hardcase by prying gently against the middle seem and breaking the bond between the two halves.  If you do this correctly you can reuse the hardcase when your done.
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    Now that we have the cells themselves in our hands we can see that this pack has an internal lipo balancer, these are used in some high end packs to keep idiots from destroying them, but they do eventually fail as this one has and must be removed.  Make sure to use a GOOD soldering gun and have a soldering stand as you can see to hold the wires to keep from burning yourself, this stand also comes in handy later during reassembly.
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    Remove the balancer from the pack with all the leads to it and set it aside for later.
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    Now we have a bare two cell lipo pack, remember to mark + and - on the pack so you know were to reattach the leads at.
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    Next we need to make a new battery lead for the pack, start by pre-tinning the leads at the end of the wires.  Make sure that you tin the exposed wire completely.
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    Next we will begin soldering the leads back to the pack, remember to use a high heat gun, and make sure you puddle the solder so when your done it looks smooth and shiny, a dull solder job is weak and will fail.
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    Next you need to reattach the balance tab, all balance tabs are wire the same, the black go to the negative of the pack and the next lead goes to the positive of that cell, and this process gets repeated for however many cells there are in the pack.
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    Lastly tightly wrap the pack in some decent electrical tape, do not overdue it, this is to only hold everything in place and insulate some, DO NOT make a cover from black tape!
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    Ok so now it's time to make this look good again, remember the hardcase we took apart, well now were going to mod it and reuse it.  I like my wires to exit from the side so I made a hole in the side of the case for the leads and balance tab to exit
    [​IMG]

    Next fit the pack in the case, remember it needs to be a snug fit, I like to use foam to insulate one end of the pack so it still has some movement in the event of a crash.
    [​IMG]

    Now snap the two case halves together and reglue and your done!
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    Last thing to do is check the pack and see how it performs, I prefer to use my e-station.
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    I hope this helps at least one of you, this repair took about 30 minutes start to finish to complete.
  2. GPBill

    GPBill Registered

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    Thanks for making the time to post that.  ;)
  3. GPS

    GPS Registered

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    That was great, thanks for sharing.  I know you told me what you were doing, but it's even better when we can see it.
  4. smitty

    smitty Registered

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    Thanks sinistercad, you made that look easy.


    Q. Would you ever fill in the holes and gaps in the hard case with hot glue or silicone?
  5. sinistercad

    sinistercad Registered

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    No I won't as there is no need, Lipo batteries are waterproof and sealed permanently, so there is no need to goof with them.

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