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Paulpod avatar image

712 monitor not showing correct % battery charge

BMV-712 battery monitor works properly with all functions after install with the exception that the battery % charge does not reflect the inverter recharge. The percentage goes down as the amps are used, and when the monitor is rebooted (disconnect and reconnect) it goes back to 100% and starts the process over. @Paulpod

BMV Battery Monitor
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Hi @Paulpod. Has the parameters been set up correctly on the BMV? It is normal for it to revert to 100% on a reboot, once all the settings are done correctly a reboot is not needed

Hi @Paulpod. When power to the BMV-712 is disconnected and reconnected it will always show 100% SOC. This is the way it has been designed to work - since it cannot know what charge or discharge happened to the battery while it was powered down. The BMV-712 normally requires a couple of uninterrupted charge/discharge cycles to accurately display the real battery's state of charge.

1 Answer
Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

Hi @Paulpod,

It sounds like the inverter/charger NEG is not connected to the BMV shunt as is required for the shunt to measure the charge being put back into your batteries; the reason it reverts to 100% SOC when reset is because the "automatically start at 100%" option is selected, not because it's actually measuring a 100% SOC.

The only thing connected to your battery NEG terminal should be the "battery" side of the shunt, and ALL other load, charge, and chassis NEGs must be attached to the "loads and chargers" side of the shunt. It sounds like your inverter/charger NEG is connected directly to the battery (or is bypassing the shunt in some other way) and thus the shunt isn't measuring the current being put back in. Please double-check that your connections at the shunt have been made in accordance with the user manual and report back!

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