[chbot] Battery Pack - the 27 chocolate fish challenge

[Kay edgecumbe]

most of the connecting straps are thin stainless steel alloy and i just use a sharp knife so that there is a tab to solder to  .
in the case of a dud cell then leave the cell connector as long as possible.
been there done that many times  and the tags seem to solder well with a larger soldering iron  ie 30 watts plus

> Date: Tue, 18 Oct 2011 09:06:03 +1300
> To: chchrobotics at lists.linuxnut.co.nz
> From: markaren1 at xtra.co.nz
> Subject: [chbot] Battery Pack - the 27 chocolate fish challenge
> 
> Hi All,
> 
> Last night Paul L was kind enough to give me a busted battery pack 
> from an electric drill - www.idesignz.org/BP/battery_pack.jpg.
> 
> The pack contains 10 x 
> <http://www.idesignz.org/BP/DM_IMR18650E.pdf>http://www.idesignz.org/BP/DM_IMR18650E.pdf 
> Lithium Ion cells.
> 
> Two cells are busted, hence the reason for the unit being thrown out, 
> and of course they are in the middle.
> 
> The cells are capable of 20A discharge each, and two cells are in 
> parallel. Short circuit current is likely in the order of 100A per 
> cell given internal resistance of 35m ohms and 3.7V terminal voltage.
> 
> The connecting tabs are copper sheet that have been sport welded onto 
> the end of the cells.
> 
> There is a black plastic saddle that the cells are attached (glued 
> ?), with about 0.5mm clearance between cells. Max working temp is 65C.
> 
> So the puzzle of the day is how to disassemble the pack safely.
> 
> My inclination is to start by cutting vertically with an abrasive 
> non-metallic dremel disk - at least the neighbours will be isolated then.
> 
> Might then be tempted to soak in white spirit to dissolve the 
> adhesive to the black saddle, but that may do nasty things to the 
> green cell insulation.
> 
> If you short adjacent cells you **will* start a very nasty fire.
> 
> Any other thoughts ?
> 
> -Mark
> 
> 
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