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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
Hi all. Well, it looks like we may have a new source of thick copper foil for making TC/induction/etc PCBs.
Managed to get around to testing some of those defunct LiPo cells I salvaged from the dead Macbook packs. As expected most of them are at or near 0V so no way to recover them, so its gutting time.
Procedure:- Check cells are at 0V , don good quality gloves and goggles then carefully open OUTSIDE! and drop cell into water. Wait until the reaction (if any) stops then unpeel the cell and unwrap the jelly roll structure under the water, being sure not to tear the copper foils.
This is important because if you try "dry peeling" the cell then leave the copper out, the residual Li in the graphite will turn the copper into fragments of copper oxides in short order.
Once unwrapped, you may be faced with one of two cell types. The first has the graphite bonded directly to both the copper and the aluminium, so to salvage this you need to leave the foil in the water until the graphite easily comes off.
The second has an intermediate PVDF sheet between both sets of electrodes, presumably to keep the paste of graphite and CoO2/MnO2 in contact with the electrodes. These are essentially ready to use, just make sure the copper is well rinsed and then recycle the rest.
It also appears that with many of these cells if they have "puffed" the end 20cm of the foil usually oxidises. If this is the case discard this section, and salvage the remaining copper.
For a typical 3Ah cell you might find, there is about a metre of copper foil inside as wide as the cell. This equates to about 4.5 grams of copper which can then be hot foil glued to either a sheet of glass or an existing single sided board to make it double sided. I've had some success with superglue but it needs to be absolutely flat to "take" and this is a messy process. Better to use glass and UV glue it in place so you can see any unstuck spots and rectify this prior to setting.
This procedure is only really feasible with LiPo pouch cells due to the hassle with opening conventional Li-Ions, not least that these have usually built up pressure in use and can be dangerous if dismantled in this way.
Can anyone suggest a use for all that PVDF porous sheeting?
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Salvaging copper sheet from dead LiPos
