Should pouch cells be in constant external pressure?

[neptronix]

doctorbass was a big fan of mild compression but i ran RC lipo for 5 years over ~600 cycles with great success..

I personally don't like compression because the cell's ability to puff gives you time to notice a problem building up that's causing a pack or just one cell to puff up..

When you compress you remove that small safety margin ( allowing the pack to visibly deform as a warning of what's next to come ) and lithium batteries don't have much of a safety margin to begin with.

 

[DogDipstick]

but i ran RC lipo for 5 years over ~600 cycles with great success..

600 cycles? Noh... no.

We are talking 10,000+ cycles with these EV lipos.

 

[rg12]

doctorbass was a big fan of mild compression but i ran RC lipo for 5 years over ~600 cycles with great success..

I personally don't like compression because the cell's ability to puff gives you time to notice a problem building up that's causing a pack or just one cell to puff up..

When you compress you remove that small safety margin ( allowing the pack to visibly deform as a warning of what's next to come ) and lithium batteries don't have much of a safety margin to begin with.

That's exactly what we have discussed in this thread.
The fact that the cells have pressure on them helps to eliminate/reduce the gas formed inside of them.
So by not letting them puff, they don't puff.

 

[rg12]

I

I don't think you need to put any pressure on the sides of a stack of pouch cells, just 2 endplates

For side plates you need room for their thickness and straps/bands to press them and that can take 1cm easily which I don't have.
Putting pressure inside can have alot more pressure then plates without taking any room.

 

[floydr]

For side plates you need room for their thickness and straps/bands to press them and that can take 1cm easily which I don't have.

A pressurized box sounds like a problem just waiting to happen. If the space can hold a box with the battery in the box you could make the box strong enough to hold the battery adding a couple of spacers if needed to provide the compression(2-3psi .20 bar) IE the ends of your box are the compression plates. Provided that box is strong enough with vents would work without coming a bomb if the cells vent.
Later floyd

 

[rg12]

A pressurized box sounds like a problem just waiting to happen. If the space can hold a box with the battery in the box you could make the box strong enough to hold the battery adding a couple of spacers if needed to provide the compression(2-3psi .20 bar) IE the ends of your box are the compression plates. Provided that box is strong enough with vents would work without coming a bomb if the cells vent.
Later floyd

Yeah that was my next question about a case of fire in a pressurized box and what will happen...
Will go with your solution then.

One more thing...
I see that a certain manufacturer placed the cells in an alternating way.
The cells have a side where one side has the edge folded and one side is more flat.
I like to place the cells in a way where all the folded edges are on the same side but I have seen a pack that I have that a certain company built where they have alternated the cells and the tabs weren't touching all of the surface since the tabs aren't centered in these cells.
I'm wandering why this company insisted on alternating which it makes the tabs to not be aligned and have much less surface area connected.