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Dala
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Pressure testing batteries

Tue Jun 02, 2020 3:23 am

AKA Air leak inspection
So here's something that's good to know when testing used batteries. I recently examined the 40kWh that is soon going into a customer car, and found a small puncture in the top casing. After informing the customer, and then repairing the small puncture, it was time to pressure test the battery.

So a bit about pressure testing. The batteries are by design "waterproof", this specific model can be fully submerged for a few minutes/hours? without any issues. But they aren't 100% waterproof, some water will get in thru the high voltage harness pins overtime, so it's not possible to store the batteries underwater. So to test the batteries, a pressure tester is needed. There is an official tool, but since it's not possible to buy it I'll have to make my own.

Here is the port on the battery used for testing. It's just a bolt with a copper washer, next to the high voltage connections.
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And here is my improvised tool using some scraps. It's just the same bolt type, with a hole drilled thru it. I put some threads into the bolt head, and attached a hardline pipe and hose to it. It then gets a bike tire pressure valve on the end, which a normal bike pump can be attached to. Tada, 0€ testing tool.
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And finally here is the official procedure from the FullServiceManual.
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And yes, the battery passed the test :)

goldbrick
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Re: Pressure testing batteries

Tue Jun 02, 2020 8:27 am

Nice work, as always, but where do you find a gauge and pump that can operate at 1.6kPa/0.232 PSI ? That seems tiny compared to most applications and I wouldn't know where to find that kind of equipment. Just curious as the check valves on my bike pumps are iffy at best when inflating bike tires and I can't imagine any consumer pressure gauge being that accurate.

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Dala
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Joined: Sun Oct 28, 2018 11:24 am
Delivery Date: 01 Jan 2015
Leaf Number: 316851
Location: Finland
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Re: Pressure testing batteries

Tue Jun 02, 2020 9:06 am

Ebay has them(Precision Air Regulator), but I think the manual is overly cautious to not have you pop the breather valves out (these are the ones that should go first). So you might get away with a bit more pressure if you're lucky. But better safe than sorry :)

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Nubo
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Re: Pressure testing batteries

Tue Jun 02, 2020 11:17 am

The mildest pressure test ever. A blood pressure kit would be overkill if not for the volume.
I noticed you're still working with polymers.

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