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Proper way to charge 12V bank from 48V bank ?

Hi Forum. This boat has 48V battery bank with some 12V loads that draw more than 30A. I was thinking of a Victron DC-DC converter, but doesn't it make more sense to use a DC battery charger to ensure that an absorption charge happens when necessary ? I'm curious what others recommend or do in such a situation ?

battery chargingOrion DC-DC Converters not smart
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2 Answers
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rickp answered ·

I'm no expert, so if I'm off base I am hopeful I'll get corrected here!

If I understand you correctly, you're asking why not use a 12 volt charger for power supply to some 12 V loads, and get some battery charging at the same time. The problem is that you have a 48 volt battery bank that needs to see that voltage (actually higher, in the mid to upper 50s) from a charger to replenish itself. A 12 volt charger wouldn't do you any good, and a 48 volt charger can't supply 12 volt loads.

If you have 12V loads currently in use, there must be a converter in your setup already. If this is something you're looking to add, Victron does make a 48/12/30A version that sounds like it might suit your needs.

My setup is 24V, and I use a Victron Orion 24/12/70A to feed a fuse block for 12 volt loads. I like it because you can set the voltage output to suit your needs. Some converters put out 12.6V or so, and 13.2 (the voltage of a charged 12V battery) just works better.

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sven-nurber answered ·

Thanks for reply RickP. It would seem that the right way to do this is DC DC battery charger, but Victron doesn't make one that I'm aware of ? Analytic Systems does, but as this boat has 12V alternators I'd also like to be able to charge the 48V LFP from the 12V bank so in the end I'm really looking for bidirectional DC DC charger or something else. May have to get separate devices for 48>12 and 12>48 paths. I'm do some more digging.

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