 Dismantled LiFePO4 DX cell
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Conundrum
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Mon Apr 25 2011, 04:58PM
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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
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Hi all.
I finally got around to taking one apart, it measured less than 1V after charging so it was obviously not fixable.
Looks like the cell areas are as follows.
77.5cm FePO4 (cathode plated onto what seems to be Al foil, sticks to magnet!)
76cm carbon (anode plated onto copper foil)
5.7cm wide
Both are double sided separated by what I assume to be PVDF soaked in an aqueous electrolyte which is probably a lithium salt such as LiCl.
This gives a total cell area of (77.5*5.7) *2 = 883.5 cm2
As you can see there are various safety features in this cell, such as thin tearaway tabs which are 3mm wide by 0.1mm thick, safety vent on + cap and what appears to be a polymer based thermal fuse.
According to the relevant articles on Google the efficiency is 274 mAh per gram of active material.
Judging by the amount of active material in this cell and online feedback on these cells I would expect the capacity to be around 1.1 Ah which is a lot less than the 1.35Ah quoted.
The cell has a few bad spots when unwound so this might explain the poor performance.
I might try charging a segment to see what it does.
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