ok to mount Chevy Volt batteries upside down?

Only thing I can really think of is if the coolant leaks from a hose or something. If they are upside down the box should definitely have a drain hole, otherwise coolant could get on the cell tabs/bms board and cause a short. I believe that was the root cause of the Volt that caught fire at the NHTSA lab several days after the car was in a rollover test. Took that long for the coolant to dry, the residue to start conducting and the cells to discharge beyond safe levels.

Other than that, flipping them might be a bit of a pain so maybe make a tool to support them from the flat surface above the coolant passages so you can hold them while tightening the oem foot clamps (assuming you plan to re-use those?)

thanks @Zieg. great info. Yeah, I'm not using any of the Volt BMS modules, but the BMS wiring that goes to each cell is obviously up there.

Planning to re-use as much of the mounting structure as we can!

Oop, yeah when I said module I meant the actual battery, sorry. That's where the short occurred on that NHTSA volt iirc.

Zieg said:

Oop, yeah when I said module I meant the actual battery, sorry. That's where the short occurred on that NHTSA volt iirc.

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very interesting. do you have a link to this NHTSA lab test?

You also really don't have to run Chevy red coolant. Plain de ionized works well unless you live where stuff freezes. I suppose you could also use mineral oil or silicon something that is non conductive, but the NHTSA didn't examine specific methods of fire prevention. @Zieg has it correct about the BMS/wiring being the failure point.

great info. thanks! I'm happy to hear that it took about one week for it to become conductive.

Crystals from coolant evaporation is why it took a week. No, it wasn't the BMS wiring, but a short from a pool of coolant in the connector shell, which was never foreseen to be upside down, let alone filled with coolant that then evaporated.

Using a dielectric, like DI water, is a bad idea...the charge buildup could take out your electronics. Might as well pump cat fur through your modules 😂
Unless you have $ millions for R&D and qualification testing, ride the coattails of factory engineering.

The coolant loop plates appear to be designed as a siphon. Not sure what would happen when you turn them into a manometer.

If you can get ALL of the air out, and ensure no entrained bubbles ever accumulate later....

well, most of us want to benefit from the factory engineering as much as possible... I certainly do... but obviously there will be areas that you will be forced to diverge given that... we're installing it in a different vehicle and all.

For this particular decision, I am struggling to find enough room under the hood without mounting one of them upside down... but I will keep searching.

Understood.

You're the only one that can decide the tradeoffs.

The main thing is amassing all the relevant info for that decision and figuring out a way to derisk the iffy stuff.

It might be useful to look at an earlier thread, 911 RSR with Tesla Motor... The placement of the Volt modules is shown starting about 44 posts in. In that project the modules are not all upright, but I don't recall if any ended up completely inverted.

The bms/ connectors are the only things in the tops of the battery shell, power exits the sides. The preliminary report I read didn't specify.

If there's no air entrapment, orientation shouldn't matter if there's consistent flow/pressure However: one thought did come to mind: the vents are between the electrodes on top. If you have a venting episode, you get volatile solvents escaping instead of gasses. Bad juju.

brian_ said:

It might be useful to look at an earlier thread, 911 RSR with Tesla Motor... The placement of the Volt modules is shown starting about 44 posts in. In that project the modules are not all upright, but I don't recall if any ended up completely inverted.

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oh man... that thread is AWESOME!!!! I wonder if he is still active on the forum. You're right that it looks like he wound up laying them on the side and not completely inverted, but the best idea in there are those cardboard mockups! those are fantastic. Always nice to see someone who has worked through similar problems as you. And in one of his videos, he backs out of the driveway right next to what appears to be a Porsche 944!!! I've got to get in touch with him... it's on my todo list.

Thanks so much for directing me to that thread.

anybody know where to get the bms plug on top of the battery to just check the cell votages? or a plug that may fit it?? thank you

Swogm said:

anybody know where to get the bms plug on top of the battery to just check the cell votages? or a plug that may fit it?? thank you

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i haven't found the ones that go into the top of the battery, so I just took the existing cable harness and cut them off and tied into the wires. BUT... although I haven't tried it, I think the plug size is basically the same as the molex connectors you might see on an ATX power supply, so I think you could trip and modify some of those plugs to connect well, although they won't have the retention mechanism.

That will vibrate loose in the car.

While you could do it for bench work, in a complex build there's a chance it will be ovelooked and stay that way.

We tend to overlook the simple stuff, and that applies for checking for mistakes.

lordmundi said:

i haven't found the ones that go into the top of the battery, so I just took the existing cable harness and cut them off and tied into the wires. BUT... although I haven't tried it, I think the plug size is basically the same as the molex connectors you might see on an ATX power supply, so I think you could trip and modify some of those plugs to connect well, although they won't have the retention mechanism.

Click to expand...

yea I dont have any of the plugs would like to buy at least one
but will look In to the atx molex
thx

beats taking the covers off to check each cell
have about 96v of them

NO RETENTION MECHANISM for the Molex.

So, no, it doesn't beat taking the covers off and measuring each cell: