robk avatar image
robk asked

BMV712 Not Registering Solar Charge Amps

I have the following in vehicle 12v, house battery charging/monitoring system :

My AGM deep cycle batteries (360Ah) are charged through a DCtoDC 40A charger/mppt solar controller, connected to the vehicle start battery and 600w of solar panels. Also installed is a Victron IP22 240v to 12v charger.

I use a BMV712 which registers Amps used, when my fridge, lights etc are in use. I understand the 712 Current usage is Net ie Charge current going into batteries Less Current Used by Appliances/loads.

If my State of Charge is 75% and power is only coming in from Solar at 22amps, as shown on my Charger/mppt controller, with all appliances/loads switched off, the BMV712 shows 0.0 A.

Current used by appliances is correctly being registered. This results is SOC % battery capacity, always being understated and way below true SOC. So SOC might show 60%, just before the 712 hits the Charged Voltage setting of 14.3V ( Charger absorption voltage is14.6V), and auto syncs back to 100% SOC. Tail Current is set at 2% (7.2A) and Charge Detection time to 10 Minutes.

I suspect solar charge current is not being registered due to incorrect Shunt connection.

The LOAD connection of the shunt has :

1) one heavy cable, earthed to the vehicle chassis

2) Fridge Negative cable

All other appliances load/negative cables connect to a Bus Bar which is earthed to the vehicle body

The Shunt Battery connection has one cable connected to the connected batteries Negative pole. It's the first terminal on that pole, with the Battery connector terminal above it and the Charger/Mppt Controller Battery power Out Negative cable on top of that. Does this also need need to be connected to the Shunt LOAD terminal ?

BMV Battery Monitor
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1 Answer
JohnC avatar image
JohnC answered ·

I think you're onto it Rob. Everything you want to measure must pass through the shunt, whether or not it's a LOAD or a charge. The terminology may not truly suit, but the BMV is a 2-way device, and that's the only way for it to track the batt as a whole.

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