uncledoug avatar image
uncledoug asked

Can a bmv 712 monitor the battery charge status of a 48 volt system that is charged by 4x12V battery chargers?

I have a electric powered boat that runs on 48 volts. I use 4 12 volt golf cart lead acid batteries. I charge the system with a 4 bank 12 volt charger. My question is can then 712 monitor the charge or the batteries if the charger cannot be run through the shunt. If not can i reset the unit to full charge every time I charge the batteries. My goal here is to not discharge the batteries to a destructive state. Thanks in advance Doug

BMV Battery Monitor
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1 Answer
kai avatar image
kai answered ·

Interesting - I think it can work. Do you have a drawing, I'm guessing at how the circuit is set up.

The shunt would cut into the return path for one of 4 charger banks, which is also in the motor circuit. When charging, the shunt would only monitor the current going into one of the batteries. Assuming the batteries are balanced*, it should be ok. Then of course, when the motor is being driven, the current is flowing the other way and the shunt count the charge out.

* -> You do need to be sure that the batteries are balanced before you rely on the SOC of a single 12v bank. How you do that is up to your charging process and any other balancers you have in circuit (more info?)

Note: without looking again the specifics of the BMV and your circuit, wire the BMV into the lowest bank relative to ground. e.g. the one at 0-12v, not 12-24 or 24-36, etc when its series'd up to 48v.

Of course, you can always just check (either manually or with a device) the voltage of the batteries and base your decision to motor on that. The SOC is useful if you want to get a sense of - "I'm roughly at X%, need to get back to shore". If you're just after "don't kill the bank", then voltage check might be the (easier) way to go.

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