Monitoring cell temp + bulge?

Batteries, Chargers, and Battery Management Systems.
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inh   1 mW

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Monitoring cell temp + bulge?

Post by inh » Jul 05 2013 7:49am

Ive been playing with the idea lately of droppign a thermistor between each cell and on the ends of teh pack to measure cell temperature, which seems like a decent idea. The other idea is to use a felx sensor on each side of a LiPo pouch cell to try and detect a bulged pouch, though I'm not sure how well that would work since the cheap flex sensors seem to change their base resistances on tehir own after a few weeks :roll:

Anyways, just interested to see what you guys think. Cell temperature could be done cheap and seems like a great thing to have, if for nothing else than when charging...

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bowlofsalad   1 MW

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Re: Monitoring cell temp + bulge?

Post by bowlofsalad » Jul 24 2013 6:05am

While it might be cheap, would the thermistor be difficult to install? Is it possible to keep all the cells in a smaller region and detect temperature in there? I don't know if ventilation is something to consider for packs that get warm.

Personally, I think the wise thing to do is to avoid designing something on an ebike that is going to get very warm. That means setting lower amp limits, slower travel, larger packs, higher C rating or something like that. I don't know what your application is or what the ideas are involved, so maybe it's silly to consider what I am suggesting for your goals. I imagine that many applications could accept larger battery capacity or you could live with a lower amp limit.

davec   1 kW

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Re: Monitoring cell temp + bulge?

Post by davec » Jul 24 2013 6:40am

I don't see the point unless your totally stressing your cells and drawing high C out of them- or the cells are old and have high IR
i've done many trips with my calb cells and they stay ice cold
some of the professional built modules do have these sensors in place going to a BMS

wb9k   10 kW

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Re: Monitoring cell temp + bulge?

Post by wb9k » Jul 24 2013 7:50am

It's an excellent idea. Apparently from the comments, thermal monitoring is rare in the BMS's this community is using. From a safety perspective, it's a must-have in the automotive world, and the data can be used to tell you all kinds of useful stuff--especially in all the one-of-a-kind (essentially prototype) packs I see around here. Do it. The more coverage you can reasonably get, the better.
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