Positive end of pack always hotter

[John in CR]

I've noticed that the "+" end of my Lifepo battery pack is always hotter than the rest of the pack after a ride. I recall reading somewhere about the end cell(s) getting more stress than the rest of the pack. I'm unsure of the cause, but I know enough to know that heat generation is the enemy. My question is this, does it make sense to double up on the paralleled cells at the "+" end of our battery packs to fight this effect?

John

 

[Parker]

I was thinking it would be nice if I could rotate or reposition my cells to spread out the stress on
the end cells.

 

[Link]

I think that was my post. I still haven't found a satisfactory answer as to why this happens. :?

 

[Anonymous]

.

 

[dogman dan]

Wrapping an aluminum cookie sheet around my ping pack really helped it dissipate the heat faster. Hopefully this is helping the middle cells cool too, but the end ones are definitely cooler now. After a big ride, the pack was taking about 2 hours to cool off to room temp, but now it does it in about 45 minuites.

 

[John in CR]

Wrapping an aluminum cookie sheet around my ping pack really helped it dissipate the heat faster. Hopefully this is helping the middle cells cool too, but the end ones are definitely cooler now. After a big ride, the pack was taking about 2 hours to cool off to room temp, but now it does it in about 45 minuites.

Good info and reinforces my desire to build aluminum batt boxes once I decide on a shape.

 

[fechter]

All the cells are in series, so the current is the same in all of them. I can't think of a reason why the one on the end should get hotter than the rest, unless maybe the cell tab is different and it heats more. I suppose the end cell would be more prone to getting hit or dented.

It seems like the end cells would get better cooling, so go figure???

 

[bquick]

Here's a theory:

Heat in the cell is dissipated mainly through the metalic parts of the cell. The negative metal is connected to the outside of the cell, where the heat is easily dissipated to the atmosphere. The positive metal only has a small area exposed to the atmosphere, so it's harder to dissipate the heat. So, the positive end of the battery probably more closely represents the internal temperature of the cell.

- Brad

 

[Rassy]

Okay, you got my attention. When I got my duct tape (anna) packs, I was more concerned with physical damage than heat problems. Since they were built with cardboard and ducttape, I first wrapped them with a couple layers of small bubble wrap, then added a piece of thin hardboard (showerboard?) to each side, and wrapped it all in another layer of duct tape. Well nothing ever gets hot - on the outside! On top of that, they are riding on my rack in an insulated cooler bag. Should I be concerned? I often pull over 30 amps from the 20 AH packs. Thanks.

 

[vanilla ice]

I'm not sure its relevent but when welding most of the heat goes to the positive side.

http://weldersmk.blogspot.com/2007/09/direct-current-electrode-positive.html