Compressing pouch batteries to lower IR

[mwkeefer]

Luke,

Have you ever done any canning... that roughly the opposite of what we want to do right? Im beginning to think that an aluminum compression box (like a bolt down C clamp) would do a much beter job of:

1.) Physically adding pressure to cell blocks
2.) Thermal dissipation

Then if that were encased in even lightweight ABS enclosure and pressurized with a CO2 canister or some similar method (I suppose you could use air from a gas station in essence but I would want CO2 or some other inert gas to combat combustion.

Thoughts? (you are right about the PITA part, but maybe worthwhile in the long run for lifespan increase)

I suppose it would be kinda funny eh, rolling into the gas station to check the pressure of your tires and battery enclosure? Could build it with a little shrader valve type fitting with a pressure guage built in... - sorry thinking outloud (sort of)

-Mike

 

[liveforphysics]

Luke,

Have you ever done any canning... that roughly the opposite of what we want to do right? Im beginning to think that an aluminum compression box (like a bolt down C clamp) would do a much beter job of:

1.) Physically adding pressure to cell blocks
2.) Thermal dissipation

Then if that were encased in even lightweight ABS enclosure and pressurized with a CO2 canister or some similar method (I suppose you could use air from a gas station in essence but I would want CO2 or some other inert gas to combat combustion.

Thoughts? (you are right about the PITA part, but maybe worthwhile in the long run for lifespan increase)

I suppose it would be kinda funny eh, rolling into the gas station to check the pressure of your tires and battery enclosure? Could build it with a little shrader valve type fitting with a pressure guage built in... - sorry thinking outloud (sort of)

-Mike

That does sound like it would be a good way to do it. I really truely think that the consistant 100lbs or so of constant force you can apply to the cells simply by wrapping the stacks of packs with electrical tape is enough IMHO. Save that energy/time/materials towards building something super cool, like a DIY axial flux motor or a caveman controller

 

[mwkeefer]

True - I suppose though this would make for a good experiment for someone with adequate time to do the work (I've got too many experiements in the air right now). Im interested to see if it would extend the lifespan of a pack though... notable impact on life would be required... maybe a 10-15% increase minimum before it would be worth the time/energy.

In the car world, I've spend 100s of dollars to gain 2% or shed a hundred lbs of weight to get better 1/4 mi times... it seems as if the ROI required for eBike / LEV is at minimum 10% gains... opinions?

-Mike

 

[StevenR]

It sounds like A LOT of work and someone has to prove it does ANY good beyond what tape can do in the first place. I would spent a good deal or put in quite a bit of work if there were some assurance of a 2% improvement. I would move heaven and earth if I could pick up 10%...

 

[VRdublove]

Going back to the affect that temperature has on the performance of LiPo, I've noticed a surprising bit of lost power if I let my trike sit out in the 20 degree fahrenheit weather for a while. My packs are insulated, but I'm going to re-insulate them with higher R-value cellulosic insulation. Is there ever a point (in the summer) when these can get too hot? Keep in mind that I have a 15C, 25 Ah pack that's capable of 375 amps continuous but rarely sees over a 250A draw.

Thanks

 

[johnrobholmes]

Over 140f is danger. 120f is really the best zone to keep them for lowest IR.