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.
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.
And finally here is the official procedure from the FullServiceManual.
And yes, the battery passed the test