I have had my BMV for 3 years and I love it. Its tells me more than I need to know.
About a month ago, I disconnected my motorhome from shore power and turned off the AIMS inverter/charger. All would have been fine if I hadn't forgotten to flip off the Use/Store switch which left the smoke and CO detectors energized, drawing about 0.65 A. After about 652 hours (27 days), my four AGM batteries must have depleted to zero.
Yesterday, I reconnected the shorepower and today all is back to normal. The SoC is at 100% and voltage is 13.48. I was able to verify in the BMV history that the SoC actually did reach zero volts.
My question is how the BMV history was able to survive.
According to the specs, it needs a supply voltage of at least 6.5 volts to operate and it draws about 3 mA at 12 volts.
When the SoC fell below 50%, it should have gone into an alarm condition, closed the relay, and started using more than 15 ma.
How was it able to measure zero volts and record that condition in the history without a power supply?
Does it contain a non-volatile memory chip? Maybe a CMOS memory chip with a tiny battery?