Compression of pouch cells, info/data

[john61ct]

Sure but when you want major kWh fiddling with hundreds of itty bitty cells is a pain.

And honestly, all you need is metal plate and some strapping or threaded rods, really NBD.

Especially starting with the hard-cased prismatics like your Winstons.

 

[john61ct]

My error in using "puffing" ... as puffing is a NO NO. What i should have said is "expansion" as it relates to this post

Nope, puffing is just greater expansion than should normally be allowed.

Just prevent it is the bottom line, no rocket science needed unless we're talking some well-funded mission critical scientific or corporate project.

 

[flippy]

Sure but when you want major kWh fiddling with hundreds of itty bitty cells is a pain.
And honestly, all you need is metal plate and some strapping or threaded rods, really NBD.
Especially starting with the hard-cased prismatics like your Winstons.

if your packs are getting big then the compression also gets to be a pain to prevent the side plates from bulging. you need thicc plates or extra bars to strengthen it. no to mention keeping everything together in an already big and heavy package.
if you have a solid process its not much harder then welding blocks of 18650 or bigger cells together. especially if weight, size and cost is a factor. dont forget that 18650 is still the cheapest per kWh. for most people here labour cost is not really a factor so the time factor does not really apply. you still end up with a smaller, cheaper and lighter pack when you did with lifepo or worse: LTO.

 

[methods]

I have 8S 40Ah of 2018 Ping LiFePo4 made up of soldered 5Ah pouches in 8P. I am pressurising to 4.20psi doing leak-down tests (cycling)

At ambient... The cells are always outgassing. If kept in any sort of semi-sealed enclosure the whiff of electrolyte is strong and distinct. They've been doing this for years and years....

This particular pack is headed for open water testing between the Santa Cruz harbor and the Warf.

If anyone is aware of limits I can avoid, tips would be appreciated. My pressure vessel will exceed 4.20PSI but I've been trying to work closer to 2.5 or 3 PSI out of unknowing fear.

... There is always a constant leak
So if I could run even one psi higher pressure, That may buy me 20 minutes or 2 hours depending on conditions.

GOAL:
"CREATE A BOX THAT IS UNLIKELY TO LEAK IN THE EVENT THAT I TAKE IT TO 1/2M SUBMERSION IN SALTWATER OVER AND OVER FOR 2 HOURS"

THEORY OF OPERATION
IN MY BRAIN... SO LONG AS THE BOX IS PRESSURIZED... I CAN FEEL CONFIDENT THAT SALT WATER HAS NOT ENTERED THE ENCLOSURE

I'll let you know how it goes

-methods