Yea this is a “smart” battery monitor and will calculate the health of the batteries once calibrated correctly.
HI Diverrob. This thread is one of many on this forum dealing with the Balmar SG200, and battery monitoring in general. And I've found, from reading EXTENSIVELY on this topic, that one needs to be very careful in both terminology AND process when doing a DIY installation. What you were apparently trying to do has nothing to do with the installation and operation of a Balmar SG200. And everything to do with battery homicide.
The Balmar SG200 is an algorithmically-controlled meter that attempts to not only duplicate the older volts-amps-state of charge coulomb counter functions, but add the holy grail for most of us-how healthy (SOH) are my batteries? Balmar attempts this magic via it's algorithms that measure the instantaneous voltage and current in any battery system, storing that information, and then inferring the SOH from there. Not exactly blue smoke and mirrors, but obviously Balmar proprietary information.
And one of the tenants of the SG200 is that it is
"self-calibrating" IF YOU LEAVE THE BATTERIES ALONE. And, exercise them repeatedly to give the algorithms something to work with. And often (depending on your usage pattern) months before the actual SOH matches the number on the meter. If ever. YMMV, buyer beware, all that drivel.
Now that you've attempted battery homicide via inattention, only time will tell if you're due another trip to your battery vendor. And hopefully you've learned that loading your batteries to deep discharge states is not such a good idea. So in answer to your question, run the boat on DC overnight at the dock to get a feel for your actual SOH. Monitor water levels like a hawk, battery temperature during recharge, voltages, currents, all that electrical cha cha that is time consuming and difficult to get correct, certainly without lab-quality test equipment ala Rod Collins at Compass Marine (
https://balmar.net/rodd-collins-with-compass-marine-reviews-sg200-testing/.
Anecdotally, my wife inadvertently committed battery harikari one morning via a 110VAC hair dryer powered via the inverter when on the hook. Killed 'em deader than a doornail. I was a bit green at the time, and I was not happy to learn that deep discharge of flooded lead-acid batteries is not conductive to their health. Nor is letting the electrolyte level get low. So good luck with yours, and keep your fingers crossed.
Regards,
Pete
