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BVM-712 VictronConnect Setup - Battery Capacity Unknown

Maybe a dumb question. I have a lot to learn. I bought a BVM-712 to install in a new to me truck camper this weekend (2013 Lance 825). I will use the VictronConnect Android App to monitor. I note that the setup wizard will ask me to input the battery capacity. Unfortunately, I don't have a clue what my battery's AH rating is, and would appreciate advice on how best to proceed. The battery is a single 12 volt flooded lead acid. The label on top reads "MARINE-RV" ;"EXTREME CYCLE DUTY"; "Distributed by ABSS, Everett, WA." That, along with a yellow "8/18", is the only information provided. (I have reached out to the named distributer, but haven’t received a reply yet.)

My question is, how important is it for me to ascertain the battery’s capacity rating and input that into the app? Is it required for State of Charge and Time to Go? If I just guess, will the monitor self calibrate over time? If I should instead manually determine the capacity, any suggestions for how best to do that either using the BVM itself, or a DVM?

BMV Battery Monitorbattery capacityamps
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2 Answers
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Justin Cook answered ·

@ScoLoc, unfortunately it's critical to determine the Ah capacity of the battery and input it into the BMV; without that, the BMV can't begin to make its calculations for SOC and other readings; even more unfortunately, without doing a comprehensive load test there's no way to tell what the capacity is using a DVM or the BMV itself.

If you can measure the outside dimensions of the battery case itself, you can cross-reference that to the BCI battery size chart, and based off of that you can get at least into the ballpark of the original Ah capacity of the battery... but the Ah capacity can vary pretty wildly even among common sizes, plus of course battery capacity diminishes over time, so in the past year (the 8/18 will be either the date of the battery installation or the date of manufacture) you could have lost a significant amount of capacity depending on how it was treated in that time.

Sad to say, but you're honestly better off just getting a new battery with known capacity :-/

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scoloc answered ·

Thanks Justin,

I very much appreciate your insights. Fortunately, shortly after I posted, I got an email back from ABSS (All Batteries Sales and Service) the distributor lsited on the battery. They were exteremly helpful. They recognized the battery from my photo as one of their's with a ~60 AH capacity. They also confirmed it was sold on 8/18. I am still in the market for a new higher capacity battery. But at least I now have a number to plug into the app at set up, and there is a decent chance the battery has some life left. I am anxious to install the BVM this weekend and see what the read outs look like.

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Related Resources

Victron BMV battery monitors product page

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