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Old 05-27-2023, 04:59 PM   #126
Pat911
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Join Date: Dec 2020
Location: Melbourne, Australia
Posts: 1,919
Default Re: BMS wiring mistake?

You’re reading the diagram correctly. The very last wire is used to power the BMS with the pack positive power. There’s a seperate wire to sense the highest cell voltage and will connect to pack positive. Join them at the cell terminal, don’t be tempted to combine them and use a single wire.

This seems like doubling up but there’s a reason for it. The sense wire is used to measure the cell voltage and to supply/draw up to 2A of active balance current. This could be done with one wire but the voltage drop caused during the 2A current movement could interfere with the supply voltage. Also, the current drawn in the power wire, although minimal, could interfere with the voltage sense.

Many BMS’s combine the two, but it’s better to keep them seperate.
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