question

antonin avatar image
antonin asked

wrong smart BMV reading?

Hi,

I have been running my sailboat for the last 3 days for an average of 8 hour per day on the motor. So given our energy comsuption, the 5 agm battry pack 5 X 87.5 Ah (25A 210 minutes) for the house should be full. When running the engine the voltage on the battry pack is always above 14V, so the alternator is effectively charging.. Also during the engine running time, my 400 watts solar panel connected to my victron Mppt show no charge (0 watts on the victron connect application). I suspect the 0 w is because the alternator is charging full capacity.

Not sure if this is a relevant information but my alternator goes thru a battry isolator in order to charge 3 battry pack, the house battry pack, the thruster pack, and the engine battry pack.

Here is my problem.

My smart bmv victron iphone application show a negative current around -3.51A, while running the engine and the alternator. For the last 3 days , I have been losing approximatly 5% per day of my house battry pack, without being able to recharge even if running the alternator for extensive period of time.

Is it possible the My smart BMV is wrong and the the house battry pack is full?.

I have made a test last night when the engine and solar panel was off:

I started my nespresso coffee machine 1160 Watts and another 180w device for a total of 1340 watt and the voltage drop from 12.7 to 12.4 on the house battry pack. To me this look like full battry pack but the bmv is showing 84%??

Any idea if this can be a wrong reading of the smarts BMV?


Thanks


Antonin

BMV Battery Monitor
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1 Answer
kevgermany avatar image
kevgermany answered ·


Yes, resting voltage for fully charged AGM is about 12.7V.

Could be quite a few things.

Wiring of BMV/batteries. Battery pack negative must only be connected to the battery side of the shunt. If there is an earth/ground connection move it to the load side of the shunt along with any other connections to the negative terminal.

Wrong battery capacity and other settings in the BMV. A screen shot of these would help a lot BMV will sync to 100% when the correct parameters are set, voltage, tail current, time and battery capacity.

A heavy load like that can easily drop the voltage. Once you take the load away, voltage should recover.


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