Opening one of them up is a bit risky.
A. It's heavy as shit, hope you have a solid stand and a way to turn the thing up / down / sideways and around as you work on it. A cherry picker setup worked for me.
The pack is 300 volts, once you got hot inside, there is NOTHING protecting ANYTHING from you making a mistake and touching something wrong.
I'll tell you right now, if you DO arc flash that thing, it WILL be catastrophic. You'll damage at least one cell, to the point of auto self destruction, with no way to isolate it from the pack, save maybe getting a bolt cutters and cutting thru a bus that has how many hundreds of DC amps running thru it now.
At short circuit currents it will only take a few seconds tops for things to overheat, swell, vent and now it's a chain reaction as you have a sympathetic melt down.
Secondly, what exactly do you envision as being inside one of these packs? I have taken one apart. It isn't just a can full of battery cells. You have bus'. wiring out the ass, BMS boards,tie in boards, a bajillion nickle weld tabs. on and on and on. Then there are the communications boards, CAN bus, so on and so forth. It's a pretty complex device.
Do you really want to go gorilla footing around in it if you don't know exactly what you are doing.
I HAVE to warn you.
Opening that pack up is DEADLY. You come across that bus hand to hand you will die. 300 volts will lock you up and the rest is an old tale of carelessness and DC voltage.
Please be careful if you want to poke there.
At the end of the day it's a 20kw pack, either rebuild it for house storage at 48 vdc nom OR just get an inverter that runs at 300 volts, they are out there and not very expensive at all.
aaron