marcovicctron avatar image
marcovicctron asked

Battery charging on a boat

I have 4x 100Ah AGM batteries as service batteries in my boat, in a 12v system, There are however 3 different charging inputs. No. 1 Via the engine (80Amp engine alternator to a Victron 100-3 Battery Isolator to the service batteries main switch to the service batteries). No. 2 Via a Victron IP22 12v 30/3 battery charger. No. 3 a 100W Victron solar panel with a Victron MPPT 75/15 solar charge regulator. In normal circumstances, all 3 charge inputs would not be on together, but usually it would be a combination of No. 1 and No.3 or a combination of No. 2 and No. 3 and at night just No. 2 when connected to 220v shore power.

One conclusion that could be drawn is: I like Victron products!

But, I find it very difficult to determine all the setting for the BMV700 as well as the MPPT solar monitor in regards to charge voltage, absorption and float voltage and some I don´t understand at all, i.e: bulk and absorption time limits (MPPT monitor values) and is the MPPT monitor maximum current, the same as that of the BMV700? I find the Victron manuals very limited in that respect, hence I revert to this forum

Thank you,


MPPT Controllersbattery chargingvictron products
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2 Answers
Shane Granger avatar image
Shane Granger answered ·

Welcome to the club @MarcoVicctron. Victron make some great kit but their manuals and technical support are sorely lacking. I would love to see them take a closer look at what we users need to know and how to solve the various problems that crop up.

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JohnC avatar image JohnC ♦ commented ·

With respect. Please Vega, if you have an issue, please post it in a separate question. What you've managed here is simply to remove Marco's question from the unanswered list, so will now never be flagged as unanswered. These are often tracked by both amateur enthusiasts and Victron staffers. Marco is the loser there, but I'll try to answer him.

If you delete your answer it will also delete this comment of mine too. Your choice. Please understand..

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JohnC avatar image
JohnC answered ·

Hi Marco. Just talking charging kit (plus the BMV), perhaps just treat them as individual items. Likely you're doing that now, and have seen all the discussions of the intricacies of complex systems. And maybe think you're missing something? Relax.

The BMV I won't attempt, but it's function is largely monitoring, and to get it to show (say) a useful SOC you'll have to put in the legwork to tune it, Get to know the manual and what you're doing. It's complex, but that BMV is high-end and needs understanding. Don't fear it though.

The 3x chargers can all be run together at the same time if you choose. They may not be officially networked together, but they're all reading the same charge V.

The alternator (#1) will just attempt a set V, dunno what, but say 13.8V. The other two have charge algorithms, and will follow those thinking they're doing it alone. If you want the solar mppt to have priority, set the IP22 maybe to even the 'storage' algorithm (I'm not familiar with it), but a setting at least below the mppt's.

Just watch your max batt current isn't excessive. Shouldn't matter for short periods, and you'd only see this in 'Bulk' phase. AGM's should self-limit though, but something to watch for and deal with as necessary.

Note if you're not actually cycling the batts daily, you don't actually need to go through the higher V of 'Absorb' daily either. So makes it hard to program into firmware. You get to drive it somewhat yourself..

Hope this makes sense. Have fun..

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