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Dala
Posts: 364
Joined: Sun Oct 28, 2018 11:24 am
Delivery Date: 01 Jan 2015
Leaf Number: 316851
Location: Finland
Contact: Website

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
Posts: 1413
Joined: Tue Aug 01, 2017 3:33 pm
Delivery Date: 01 Aug 2017
Leaf Number: 311806
Location: Boulder, CO

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
Posts: 364
Joined: Sun Oct 28, 2018 11:24 am
Delivery Date: 01 Jan 2015
Leaf Number: 316851
Location: Finland
Contact: Website

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
Posts: 6067
Joined: Fri May 28, 2010 11:01 am
Delivery Date: 31 Oct 2014
Location: Vallejo, CA

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.

whereswally606
Posts: 7
Joined: Fri Nov 15, 2019 4:24 am
Delivery Date: 15 Nov 2017

Re: Pressure testing batteries

Thu Jan 07, 2021 7:42 am

Hey Dala, finding a precision air tester this sensitive seems difficult, especially at short notice given new lockdown restrictions. I thought that a 30mb gas test gauge would work ok.

https://www.screwfix.com/p/monument-too ... tid=306135

it has the bonus of being widely available and locally sourced (for the UK at least)

30mb == 0.435113 psi approximately so it feels like its in the ball park of 0.2 and 0.23psi

found an m8 bolt in my collection but its a cap head with an internal hex (from bike parts) It also maybe too long looking at your photos. Not sure whether to try to use this or buy a stubbier one to modify.

Lastly I am wondering about air valves to ensure that when I'm pumping air in the surge doesn't break the gas gauge so having a tee and a valve seems sensible to me. Another frustrating hurdle to overcome to break the seal safely on the leaf battery. (or rather put the seal back again)

Edit
Just bought the gauge from toolstation (similar to screwfix) and some m8 tensile 20mm bolts for modification. Kind of difficult to source cheap flange head ones so I am hoping that this doesn't matter too much. I really want to get my car back on the road. One thing that concerns me it that the head of these bolts (setscrews) might not be deep enough to accommodate a thread for putting an adaptor onto it. The bolts were only £0.70 pence for 10 so its worth a try anyway.

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bobkart
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Leaf Number: 307853
Location: Pacific Northwest
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Re: Pressure testing batteries

Fri Jan 08, 2021 4:22 pm

whereswally606 wrote:
Thu Jan 07, 2021 7:42 am
found an m8 bolt in my collection but its a cap head with an internal hex (from bike parts) It also maybe too long looking at your photos. Not sure whether to try to use this or buy a stubbier one to modify.
Note that you can buy bolts with holes already drilled in them ('vented'):

https://www.mcmaster.com/93235A351/

Image

Not sure that's exactly what you need, but could be close.
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Learjet
Posts: 192
Joined: Tue Mar 24, 2020 8:04 pm
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Leaf Number: 309454
Location: Louisiana, USA

Re: Pressure testing batteries

Fri Jan 08, 2021 7:19 pm

Manometer
2019 Nissan Leaf SL Plus
Build Date 2/19...car sat new for 1 year until I purchased 3/20

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Nubo
Posts: 6067
Joined: Fri May 28, 2010 11:01 am
Delivery Date: 31 Oct 2014
Location: Vallejo, CA

Re: Pressure testing batteries

Fri Jan 08, 2021 11:14 pm

Learjet wrote:
Fri Jan 08, 2021 7:19 pm
Manometer

:)
[youtube]https://www.youtube.com/watch?v=8N_tupPBtWQ[/youtube]
I noticed you're still working with polymers.

whereswally606
Posts: 7
Joined: Fri Nov 15, 2019 4:24 am
Delivery Date: 15 Nov 2017

Re: Pressure testing batteries

Sat Feb 20, 2021 1:09 pm

I managed to drill through a flange head bolt almost identical to the one that was in the pack. In the end however we never did the pressure test. I was concerned that the pump (bike foot pump) would cause too large a spike in the pressure and blow some of the seals.

The good news is that my external pre-charge resistor has fixed the car. I hope that it will continue to work but if it blows again I can easily access it near the pack disconnect in the passenger footwell centre. most the parts I used were from cpc farnell so that this could be repeated by others with the same issue on their gen 1 Leafs. I would say though that it would be cheaper to use the 33 ohm cement replacement but you will have the same issue if the relay sticks in the future when the 12v goes low in the cold.

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