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Best Way to Fine Tune Usable Battery Capacity on new BMV-712?

Just completed a usable battery capacity test starting at 100% SoC via AC charge converter on our little motorhome with two 3-1/2 year old 100Ah LiFePO4 coach batteries. My endpoint was determined by the realistic scenario of running our dual DC compressor refrigerator during the night with no other significant loads present. The compressors auto-shutdown at 10.6V, and for this test the BMV-712 showed 186Ah consumed, 7% SoC remaining when they finally shut down. I wasn't present to determine the exact BMV-712 voltage reading for compressor shutdown, but it was in the right range between two readings (11.11V and 10.25V).

My current BMV-712 settings are 200Ah battery capacity and 99% efficiency. Even though I could get some LED lighting to work after compressor shutdown, I'm thinking it would be best to adjust the BMV-712 settings to get the SoC to register 0% at the time we can no longer run the refrigerator. Does this make sense? Would the best way be to change the 200Ah setting to 186Ah?

BMV Battery Monitor
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Trevor Bird answered ·

Hello pstover,

I think that if you have experimentally concluded that the actual battery capacity is now 186Ah, it makes perfect sense to set the battery monitoring equipment to that capacity.

Regards,

Trevor

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pstover avatar image pstover commented ·

Trevor - thanks for confirming my battery capacity reset to 186Ah.

By the way, my fridge uses marine-type Danfoss compressors that draw about 3.5A each, and run independently (one is dedicated to the freezer). I was glad to see that I could get quite a bit of runtime on them even after dropping below 20% SoC. Also, I recently upgraded my solar package to 290W and a Victron Smart MPPT 100/20 charge controller with three panels in series. Useful charging now begins just as the sun peeks above the horizon. And it's nice to see the two Victron devices sharing battery data now.

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