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Heat shrink tubing necessary
#1
Hi,
I am currently building a 14S120P pack for my system. Unfortunately, the shrink tubing is broken in many cells. I stand now before the decision to replace the heat shrink tubing or to install the cells without heat shrink tubing. Tesla also inserts the cells into their packs without shrink tubing. The pack comes later in a steel cabinet and so has additional protection.
What is your opinion?


Thank you for your support

Marc
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#2
If the shrink tubing is damaged on the negative side: not a big issue.
The positive end of the 18650 cell is a completely different matter. The (-) side/casing and (+) end is only millimeters apart, and at basically the same height. A momentary carelessness with a metallic tool or watch and you've caused a short and a potential fire that cannot be extinguished. Do it right - the parts only costs pennies... and it'll look cool.

Not endorsing the following - just pointing to what sort of stuff you'll need.

Insulator rings:
https://www.aliexpress.com/item/33005413...0829840425

Shrink sleeves:
https://www.aliexpress.com/item/40000979...b201603_52

Heat gun: (300W is perfect - don't get stronger ones)
https://www.aliexpress.com/item/32953010...e6af7601e9
Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#3
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Re. Tesla: I believe it's fully automated, all steps from cell construction to putting the lid on their hermetically sealed (I think?) battery box. No real chance any careless accidents happening there.
==============
Re. Steel cabinet: It's probably painted and non-conductive, but I'd say that's an extra reason FOR having insulation on the cells.
Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#4
Heat shrinks for cells are extremely cheap. The cells obviously work fine without them, but just take the extra step to be safe. You don't want any accidents happening...
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#5
You can get exactly sized shrink wrap here: http://18650shrinkandcellholders.com/

He's a member here on the forum and does a great job. The shrink wraps are exactly cut to the right length so to not have overhang or too short. A lot of online sources are cut to a +/-1mm tolerance, for some reason.

Personally, if you don't want shrinks on your cells, you don't need them. The only place I would recommend protection would be the rings they help insulate the Pos cap from the Neg shell. The wraps are required safety. They are more of a cosmetic thing and a protection from the elements. 18650Shrink also has clear wraps if you like the silver look but want the extra protection.
Note that without the shrinkwrap, the cells won't sit properly in the standard plastic cell holders.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

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#6
Its way too easy to accidently short something out without the shrink AND insulator ring in good condition.

I would highly recommend applying new shrink.
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