New battery monitor (BMV712) - now I have more questions

[White Shadow]

I just installed a new Victron BMV712 Battery Monitor and I am quite happy with the fact that I will no longer be guessing how much juice I have left. However I noticed something that seemed very strange in one of the readings, specifically the voltage on the auxiliary battery bank (The starter bank). When I was running the generator the starting bank was showing as over 16 Volts (hovering around 16.77V), that seems very high to me. The house bank was showing 14.3V which is more what I would expect to see. When I switched back to shore power, both banks initially showed around 14.6V and after a few minutes both banks were around 13.8V. It was only when running on the generator that the start bank shot up to the 16.7V range. Is this "normal"? If not, any thoughts on why this could happen? I don't want to fry these relatively new batteries.

Specifics:
2005 320 DA
House Bank - 4 x 6V 230AH Deep Cycle Lead Carbon batteries (in series and parallel - so 12V 460AH). Installed last spring.
Start Bank - 2 x 12V Group-31 AGM Starting Batteries (1000 CCA) in parallel. Installed last spring.
Charger - PD2030 (I assume came with the boat, so likely circa 2005)
Shore Power is 12V 30A service
Generator is a Kohler 5e (also I assume circa 2005)


A picture just to show my new monitor install

 

[Skybolt]

Is the battery bank showing 16.7 while on the gen, the starting bank for the gen? If so, it sounds like your generator alternator/voltage regulator is bad.

 

[White Shadow]

Yes the starting bank is the one used to start the genny, so you may have pointed me in the right direction - thanks! I will check into that early next week.

 

[White Shadow]

A bit of an update on this. I had come across another thread discussing charging batteries via the generator (https://clubsearay.com/index.php?th...-with-kohler-5e-generator.106095/post-1251721) and one person had commented that he just removed the fuse from the battery charging circuit which would then cause the battery to solely be recharged via the regular battery charger (same as if on shore power). In his opinion this would provide a better charging profile via the charger as opposed to the alternator on the generator. I liked this logic, plus it would provide an easy "fix" to my problem. Sure enough on the front of the control panel there is a fuse marked "BAT CHRG" - I removed that fuse and fired up the genny, I then checked the voltage on the battery monitor and it was now showing in the high 13's (which is much better than the high 16's). It has been suggested that the alternator likely needs to be rebuilt/replaced which is something I will likely tackle in the future (I just like things to work), but in the meantime my overcharging issue seems to have been averted.

Item #12 from the manual:

 

[Skybolt]

@White Shadow FWIIW I don't use the alternator on my generator, it is still there but is gutted. I have it tied to my port battery because If I leave the dock I am always on the generator and always have the charger on as well. So there is that, to your point.