BMS 712 battery temperature sensor shorted??

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pras asked Dec 23, '23

BMS 712 battery temperature sensor shorted??

Hi,

If i disconnect the NEGATIVE from the battery bank, leaving the POSITIVE connected, I have a voltage and current between the Battery NEGATIVE and the vessel ground, reading -25.2V and a resistance of 0,5 Ohms. All breakers are off and source of charge disconnected.

In the same condition as above, if i connect a test light between battery NEGATIVE and vessel GROUND, the light goes on and the BMV is firing up.

When i disconnect the battery temperature sensor, its got to 0v . all to normal.

Is it normal or the temperature sensor or BMS shorted?

having Positive on the vessel ground, its seems very odd to me.

It is working as normal when all connected ( including the temp sensor). but seems that this should not occur..?

Batteries are lithium, bank voltage 26,7V

thanks for you help.

Morgan

BMV Battery Monitor Temperature Sensor

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Answer 1 · 2023-12-23T22:07:27Z

pwfarnell answered · Dec 23, 2023 at 10:07 PM

The BMV712 temperature sensor is both the temperature sensor AND the positive power supply / positive voltage sense for the BMV shunt so by disconnecting the negative from the battery you have left the battery positive connected to the whole of the negative wiring, which because it can not return to the battery means that it reaches the battery positive potential. Before you disconnect the battery negative you should disconnect all positive power supplies by pulling fuses / switching off breakers including all small directly connected devices. Hopefully you still have the inline fuse in the wiring to make this easy.

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