question

richardp avatar image

Battery protect 100A temperature under load

I have a 100a battery protect setup for my charging sources. I am running about 90 amps through it and have noticed that it gets rather warm after an hour or so of charging <60 degrees.


Is this normal?


my setup is a 12 volt lithium, I have followed the 'van installation' and I am using a B2B charger that supplies the 90 amps.



Battery Protect
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1 Answer
wkirby avatar image
wkirby answered ·

I presume you have the 12/24V version?
The configuration of the MOSFET's in this version equate to an on resistance of ~0.0006Ω at 20A. This on resistance would increase as the current increases. It'd probably be roughly 0.00065Ω at 90A

At 90A the power loss within the 100A battery protect would be (I²R) 90²x0.00065 = 5.27W @ 25°C.
As the temperature increases so will the on resistance. At 60° the on resistnace would be about 1.3 times higher. So, 90²x0.000845 = 6.84W.

5-7W in a sealed enclosure will cause the enclosure to get about as warm as you are experiencing.

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Thank you for the help and putting my mind at ease. That is a very informative and clear answer.

(Yes I do have the 12/24 volt version.)


Best regards,