question

Ian Fullwood avatar image

BMV 700 & state of charge

We have a small off-grid system powering a camera - 2x 160W solar panels and 300W small turbine. Shading has been an issue (now addressed) and the system was down for a while as the voltage in our 360Ah AGM battery bank (24V) - had dropped to below 20.7V with SOC down at 41%.

Now back up and running SOC is showing 98% but voltage around 22.5V - 23.3V (varies due to wind input). Our settings on the BMV are;

• Charged Voltage: 28.4

• Tail Current: 3%

• Detection Time: 5mins

We have used the Victron video for optimising the settings but thinking that perhaps our opitmisation may have been lost during downtime? During the winter due to Northern Hemisphere location we do expect there to be drops to 70% SOC but more importantly the voltage reading at 98% SOC does not seem correct.

We are using the VRM portal to monitor the system (via Venus GX).

Are the settings we have incorrect? Any help appreciated.

BMV Battery MonitorVRMSOC
voltage-v-soc.jpg (184.3 KiB)
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1 Answer
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Ian Fullwood

The BMV resets to 100% after it has been disconnected, the battery has to be fully charged to get a good SOC reading again.

also note that with the battery below 24 volt, (and no loads) it is -empty- so not at 40% SOC

Prolonged time below 24 volt (or worse: 22 volt) -will- damage the battery and lower it's total capacity. So please adjust settings in the BMV to correspondent with the real capacity.

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