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Tutorial: Re-wrapping a Battery

Published by sonicbomb in the blog sonicbomb's blog. Views: 1837

Why does my damaged battery wrap need to be replaced?


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Before we even start re-wrapping it's vital to understand how the batteries we use are designed externally from an electrical perspective, and the inherent safety concerns.

  • Apart from the positive terminal at the top, the entire outer casing is the negative terminal of the battery. The role of the plastic wrap is to provide physical protection and to electrically isolate the case, apart from the small exposed area at the base of the battery where the mods negative contact connects to it.
  • The positive terminal at the top of the battery is separated electrically from the rest of the case by a small gap which covered by an insulating ring as an extra safety feature to help insure that this gap is not bridged creating a short. This insulating ring is as vital as the wrap, and should also be replaced if damaged and certainly never excluded.
Again, even a tiny nick in the battery's wrap can have serious consequences. Rings and other jewellery should be removed when handling a 'naked' battery as the possibility of bridging the negative and positive contacts is very real: I failed on one occasion to do this and I have now have a scar to remind me.


Now you understand the why here's the how::

Tools and parts needed -
  • Shrink wrap tubing - For an 18650 this needs to be 29mm wide. This can be bought in rolls or precut lengths. See the list of recommended suppliers at the bottom this article. Wraps are available in multiple colours though transparent ones should be avoided as it makes spotting damage to your new wrap difficult.
  • Scissors - If you use any metal object to help remove the wrap be careful not to short the battery.
  • Hairdryer - Most shrink wrap activates at about 80 degrees centigrade. Some people use a lighter or a blowtorch, I would not recommend either of these heat sources.
  • Digital callipers or a ruler - If the jaws of the callipers are metal they will need to be covered with insulating tape.

The Process -


1. Remove the old damaged wrap from the battery. Make sure you keep the insulating ring from the positive end to one side.

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2. Measure the length of the battery with your callipers or ruler, for an 18650 it should be 65mm. Cut a length of tubing allowing for approximately 3-4mm extra at each end. So if your battery is 65mm, cut a length 71-73mm long. This can vary as different wrap materials can shrink more or less than others.

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3. Slide the new length of wrap over the battery with the extra wrap extending from each end, and place the insulator ring back onto the positive terminal.

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4. Apply heat evenly to the wrap rotating the battery and swiping the heat gun back and forth, wearing a glove can help to avoid burnt fingers. Start with the top first to trap the insulating ring before progressing to the other areas. Try to avoid getting the battery too hot, but as long as it is possible to hold it then it should be fine. The wrap should shrink onto the battery long before this becomes a problem.

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5. Inspect the finished wrap to ensure that it is snug, undamaged and that ends are sufficiently covered. At the top there should be enough wrap to firmly hold the insulator ring in place. The bottom of the wrap should extend at least 2-3mm across the base of the battery. Be aware that if there is too little it may not be safe. If there is too much the positive contact on your mod may not be able to make complete contact. Excessive wrinkling in the wrap at the top and bottom may also cause contact issues. If the wrap is particularly thick or if there are wrinkles in the sides you may have issues with the finished battery being too tight in your mod.

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6. Re-label your newly wrapped battery to indicate it's model and age or any other information that you consider important.

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Shrink wrap and insulator ring suppliers -

* Based on an article written by Lhartman89
Tutorial: Re-wrapping a battery
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