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What cells are these
#1


Found thes cells in a drill battery

The ends ar 18650 but the centers at bulged out

Is this bulge from damage to cell or is there a format I have not seen before.

No markings on cell but they look to be double wrapped with a red wrap covered up
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#2
The bulging doesn't look safe. They look like re wraps. Peel off the green wrapper, it looks like there is another one underneath.

Just curious - what brand of drill battery?
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#3
It looks like someone put a heatshrink over the original heatshrink. My guess is the bulge is from the heat shrink. Remove the shrinks carefully and see what the cell looks like.
BlueSwordM and Geek like this post
#18650
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#4
Maybe just extra insulation?

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#5
It's obviously a badly put on heatshrink for used cells.
The power of lithium ion is in our hands!
We'll show them what we're made of!
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#6
There is a hard ceramic insulator covering the original Sanyo wrapper
Removed sanyo wrapper and cell looks fine

I wonder if this insulating is done To protect electronics from heaters

This is a heavy duty well built $120 battery

Learned something new today after searching

the small 2.5 Ahr or 2.0 Ahr (not sure which ones or both since I haven't taken mine apart) have a PCM (phase change material). I don't have much experience with PCMs, but I believe the concept is that they are solid at room temperature, but change to a liquid (hence phase change) at higher temperature and absorb a ton of thermal energy in the process. So these things wrap each individual cell to act as a little rechargeable air-conditioner-type system to help keep the cells cooler longer during use.
Wolf likes this post
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#7
Surprised that nobody recognized these as Ego batteries. Well, Sanyos, but as modified by Ego. They are double wrapped with the phase change material as you mentioned. It doesn't exactly turn to a liquid, more like a gel. It transfers the heat away from the cell. They have 2/4/6Ah batteries as well as newer 2.5/5/7.5Ah batteries all wrapped like that. They also space the cells apart to allow air flow during charging (the chargers have fans built in to cool the cells while charging). These batteries have all sorts of quirks to ensure long battery life, like discharging the battery to 40% if it is fully charged for more than 2 weeks at a time. For all that they did to keep the cells cool for longevity, they screwed up the BMS and there are a lot of parts only batteries. Mostly due to one transistor, I believe! Nice find!
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#8
From the picture in original post they look like repacked Sanyos. Posted this a few hours ago but something went wrong and it didn't show.
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#9
Well now the question, which is driven by extra size 
Keep the PCB gel on or remove so dia is returned to normal 18650
With the extra width these do not fit in a typical cell holder.
With only 14 cells like this, not sure if there is value to keep the pcm gel
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#10
Cool... learned something new today.
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