cedric-vincent avatar image
cedric-vincent asked

BMV-702: How do I connect 2 parallel AGM batteries?

Hello everyone!

I need some help installing a BMV-702 on my sailboat. I am sailing solo and it's important for me to know about the capacities of the batteries while I'm on the ocean.

My question: Can I connect both negative cables coming from the batteries to the battery side of the shunt and connect the loads side of the shunt to the bus bar?

Here are some more details about my setup:

Battery Setup

I have two 12v 100Ah AGM batteries installed.

The previous owner had built a box where the two batteries can be connected or disconnected to the system individually or both at the same time (see pictures below).

I would always use battery 1+2 together and frankly I don't understand why there is the option to pick between the batteries individually. From what I understood it's unhealthy for the batteries if they're used in parallel mode and don't have the same voltage.

Solar Setup

I'm using two solar panels and a MPPT 100 | 20 solar charger.

Wiring (+ Side)

I added two images, one form the outside and one from the inside of the box, where you can see how the positive side coming from the batteries and solar charger are wired up.

img-3267.jpg img-3268.jpg

The positive cable leaving the battery selection knob, goes directly to a 30A fuse before it is connected to the different consumers.


Wiring (- Side)

The negative cables of the batteries are directly attached to a bus bar, see picture below.


Thank you in advance!!

Best regards,


BMV Battery MonitorSolar PanelAGM Battery
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img-3269.jpg (791.3 KiB)
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img-3267.jpg (613.1 KiB)
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1 Answer
JohnC avatar image
JohnC answered ·

Hi @cedric_vincent

Yes, you'd combine the two battery negatives on the batt side of the shunt. With nothing else going to the batt negatives.

Good if your batts are combined too on the Pos side, the shunt needs a V reading from it's power cable too, and having that located on just one batt may cause inaccuracy issues.

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Related Resources

Victron BMV battery monitors product page

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