LiPoly compression, how much?

[TopherTheME]

For those of you that are running LiPoly packs, or pouch cells in general, how much pressure are you putting cells? What are you using to allow expansion of the cells? I've finished the battery plates and hardware for my current ebike project but still need to order some springs but don't know what spring constant to go with. I'm assuming something rather light, like say 10 lbs/inch?

 

[olaf-lampe]

I'm using foam rubber for compression. ( eg. PC-mousepad ) I have no idea, how much pressure is necessary, but I imagine too much pressure would stress the pouches' edges.
Kokam for instance stated 1-2% expansion rate during charge.
-Olaf

 

[neptronix]

lipo expands and contracts noticeably when fully discharged and fully discharged. Also, the puffing is headroom against venting, and also serves as a good visual indicator to stop charging that pack

Don't compress them too much.

 

[amberwolf]

DoctorBass has them compressed EXTREMELY tight, in one of his metal box builds. It still has an open top so if they vent they don't blow the box apart, but the sides are solidly binding them to their original size. Time will tell if this is a problem; he runs stuff pretty hard.

 

[icecube57]

I read compression reduces IR so if you compress them tightly when they discharged and you charge them you should get better performance throughout the discharge in theory.