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 Post subject: Module temperature monitoring
 Post Posted: Wed Oct 12, 2011 11:43 pm 
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Joined: Mon Sep 19, 2011 11:31 pm
Posts: 16
The rules state that Li ion temperature must be monitored per module. Where battery modules are mentioned elsewhere in the rules, a module is a manufacturer-supplied group of cells. What constitutes a module in this case?

Can a module be a student-packaged group cells wired in parallel? What if the container holds cells in series?


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 Post subject: Re: Module temperature monitoring
 Post Posted: Thu Oct 13, 2011 12:00 am 
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Joined: Mon Sep 19, 2011 11:31 pm
Posts: 16
Additionally, if a group of cells are wired in parallel (and all cells are fused) then all of the cells in that group have the same voltage. Can voltage be monitored for that group of parallel cells instead of monitoring each cell individually per table 10?


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 Post subject: Re: Module temperature monitoring
 Post Posted: Thu Oct 20, 2011 11:41 am 
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Joined: Thu Oct 20, 2011 11:09 am
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+1

what exactly does the term "module" refer to?


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 Post subject: Re: Module temperature monitoring
 Post Posted: Fri Oct 21, 2011 7:32 pm 
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Joined: Mon Sep 19, 2011 11:31 pm
Posts: 16
Thank you BYU. My guess is that "module" refers to manufactured modules. I can only guess though. It makes sense if you assume that all modules are built safely.

I have testing experience with many Chinese-built electric bicycle battery modules and very few of them are built safely. Thankfully, most of them are LiFePO4, so there's not much risk of thermal runaway. Good luck getting any of those battery systems UL approved though.

We were considering using over a thousand cells (18650s) because we could get a screamin' deal on them. Monitoring could is a problem though.

I realize that it may take time for a sanctioning body to respond to a question like this. I don't think we can wait longer though. We'll spend the money on larger cells or run lead instead.


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 Post subject: Re: Module temperature monitoring
 Post Posted: Sun Oct 23, 2011 1:12 pm 
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Joined: Mon Jun 05, 2006 4:05 pm
Posts: 112
Location: Rules Committee
You are right that the wording is vague. That will be changed in future editions of the rules. In the meantime, in the meantime, you have some flexibility, but the bottom line is that you want to make sure, or your own sake, that it's safe. That would mean that if a reasonably small group of cells is tightly coupled together, thermally, one temperature monitor is enough for that group. On the other hand, if they are separated by lots of air space, it's hard to argue that one temperature sensor would be able to detect the temperature rise in more than one cell.

Given the vagueness of the rules, if you have doubts about whether what you plan to do will be accepted by the inspectors, you might want to submit a formal query with a picture or diagram of what you propose to do, along with your argument as to why you think it will work to detect thermal failures, and get a response from the committee that you can bring to the competition to be confident that it will be accepted.


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 Post subject: Re: Module temperature monitoring
 Post Posted: Mon Oct 24, 2011 12:00 pm 
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Joined: Mon Sep 19, 2011 11:31 pm
Posts: 16
Thanks for the reply. This is a big help.


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