What happen when a battery getting too hot in a power wall

Fanard

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Hey,

I'm currently building my first power wall and i'm doing capacity test.

While i'm doing it, i got two hot cell (i can't touch them because it's too hot). I discarded them for safety.

Now my question is : what happen in a power wall when a cell is too hot? Does cid trig and isolate the cell from the others?
How do you prevent it? I would like to use PTC or other temperature sensor to prevent it. But with a 14s 100p it will require a lot of sensor to monitor a group of 4cells for example.

Thanks every one :)
 
If it have CID then yes it generally gets triggered and disconnect the cell. The CID do though trigger on pressure meanwhile a PTC does it based on temperature.

Not all cells have CID though....


Try to sort out cells that wont do your desired current. If max current is 1A per cell you NEED TO test at that current. If they get hot it can either be a Sanyou that tend to have some issues when sit for a while or even going above 4.1V. Personally i ditch those cells on 1st try. I DO NOT trust any cell that have slightest sign of issue.

There are people that tend to give 2nd chanses but for me its a big no on a powerwall supplying power to a house and in worst case even are in the house?!

You will get more opinions here but the most important to ask is do you trust your judgement or not :p
 
Please do a search for "Heaters" or "Sanyo Heaters" and you'll find many threads on the topic. I know "hot" probably returns too many results ;)
 
I'm this kind of guy too daromer :D

Same as you, any kind of default i discard cells. But here is a long term thought.

If for example i finish my power wall and all is fine. After maybe 1 year, a cell is loosing capacity and it begin to be a bad cell?

On a 14s 100p how to detect this cell and how to prevent it? If the temp is getting to high and that cell has no cid what happen?

Korishan i tryed to find something with multiple keyword but i always find cell volontary buring by human, but not a real test when is getting too hot by herself.

Thanks for you answer guys!
 
Flir Gun. Thats how you find heaters after its built
 
The CID is for pressure relief, the cells can still run hot without triggering it.

I've been doing some tests with known poor cells, of the red variety.
I know there are some that got hot during charging, but they all got mixed together at one point, and all bar onebehave normally when charged now.

So I made a battery of press-in cell holders and added cell level monitoring/logging and a load.
14s1p nominal 48V, load switches off at 40V

Of the 14 cells:
3 dropped down to 1.5V or less and got hot.
2 dropped down to ~3Vand got hot.
7 had poor capacity, 1 of those ran hot.
2 were still at 4.2V at the end of the test.

So in general the hot running cells have obviously poor capacity.
If you run a test on them individually or in 1 parallel test packs you can find most of them.
Still the odd one will run hot but show good capacity.
 
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