Lipo Battery's at depths?

[martinw]

...... they state that its "internaly pressure compensated" i'm not sure what they mean with that .....

I didn't mean to offend with the link

This report is done by some norwegian scientists(i found it by googling) and they pressure test lithium (ion i think) batteries because of a failure on a battery pack on an PIG that exploded because pressure came inside the vessel, and compressed the cells so they exploded, and then damaging the container. http://www.ffi.no/no/Publikasjoner/Docu ... essure.pdf

These are Lithium Ion cells, a completely different chemistry to Lithium Polymer cells.

Your rather simple analogy of a ping pong ball imploding is valid for ping pong balls but not really Lithium Polymer batteries, oil at pressure will tend to find its way into most cracks and crevices of an assembly of components and equalise the pressure across the mechanical interfaces by squeezing out any air in there.

Lithium polmer cells are fundamentally solid components with no air voids in them.

http://www.youtube.com/watch?v=FbVUpkoHxoU

See, no ping pong balls

When a company connects a number of cells together to form batteries it shouldn't be introducing any voids into them, just wiring them together.

I guess we'll just have to agree to disagree

Martin

[fluxno]

i was not offended or anything.. it was the "internal" terminology that made me wonder if bluefin had some special compensation system internaly in a pressure vessel.

there is a big point in this discussion that havent been discussed that much; what pressure are we talking about?
the systems i work with are rated in the area of 100bar to 300Bar (1450psi to 4350psi)
on the 300bar system we need to pressure compensate some connectors, on this we use a vacuum pump on the oil before pouring it into the cavity, and also apply vacuum after pouring it into the compensation chamber. you would not believe how much air that gets trapped in the oil just by pouring and handling.

the analogy of the pingpong ball is for air that is trapped in an closed cavity. i've seen some videos about lipo manufacturing, but have clearly not seen all steps of production. as i can see there are some vacuum steps when they form the pouch, but its not clear how much they vacum the pouch later on.

but i will agree that the lipo cells probably will withstand some pressure, but me personally would not pressure compensate lipos.

so yes, we'll agree to disagree