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Temp sensor for LiFePO4 12v battery

Tomih

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Sep 1, 2021
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Hello,

I want to place my own temp sensor to enclosed 12v LiFePO4 battery by Liitokala. Product link: https://a.aliexpress.com/_mPls2UT

Should I just drill a small hole to the cover opposite side to terminals and push in a sensor?

I want to see cell temp for not charging the battery in freezing temp and I don't trust the statement that this battery has low temp charge protection.

Cheers and thanks in advance.

- Tomi
 
I don't recommend drilling a blind hole into a battery with cells made of tissue paper

Just attach the thermocouple to the outside and call it a day. The only downside is it might cut off slightly sooner since the inside of the battery will sometimes be warmer than the air around it.
 
If your discharge and charge rate are less than 0.5C, that is, 50 Amperes discharge or charge per 100 Ampere hours battery, then the heat generated by the LiFePO4 batteries will be minimal.

If you are worried about the batteries being damaged by being charged while the cell material is cold (discharging while the cell material is cold is not as bad), then it’s ok to not drill and instead put the temperature sensor on the outside of the battery.
 
The heat will be flowing outwards from the battery to environment when reaching the point of being too cold to charge safely. That means a temperature sensor on the outside of the battery will be *warmer* than the inside cell material.

Therefore drilling is not necessary to outpace cold temperature protection for charging LiFePO4 in most cases.
 
The heat will be flowing outwards from the battery to environment when reaching the point of being too cold to charge safely. That means a temperature sensor on the outside of the battery will be *warmer* than the inside cell material.

Therefore drilling is not necessary to outpace cold temperature protection for charging LiFePO4 in most cases.
"flowing outside" does not mean outside will be warmer
just try dipping your finger in a mug with hot liquid to see if inside or outside is "warmer"
 
for clarification, heat flowing outwards implies that the exterior will be colder.

when the battery is cooling down, the interior will be warmer than outside.

when the battery is warming up, the interior will be colder than outside

by the way, welcome to the forum! ?☀️
 
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