question

james-yardley avatar image

How to charge a 48V system from a 12V vehicle alternator

Hey everyone, First post on here!

We're just in the middle of setting up our Victron system and want to use a 48v system (due to cable sizing and efficiency) in our overlander which has a 12v alternator.

My question is, can the Victron batteries be charged in parallel (i.e each batter individually charged) but drawn from in series?

If so are there Victron products or suggestions on the best way to achieve this setup, there will at some point also be some solar power introduced too, so if that could be kept in mind it would be great!

Any advice/suggestions gratefully appreciated!

James

charging
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4 Answers
bigboy529 avatar image
bigboy529 answered ·

Hi there, as already said rather consider going 24V, yes this will result in higher current draw, but it gives you a lot more options in terms of off the shelf equipment. You will be able to charge a 24V battery from your 12V alternator and you'll also be able to use the smaller Victron MPPT chargers if you go that route.

Converting from 24V back to 12V for your consumers like lights, phone charges etc. will also be a lot easier in the end.

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jwfrary avatar image
jwfrary answered ·

Hi,

A packaged 48v alternator exists, it’s called integral. And made in the uk by triskel marine.

If your going that route you may find it easier to fit the one 48v alt and step down to 12 for the vehicle loads.

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jexhed avatar image
jexhed answered ·

Hi James, did you find s solution yet ? I plan to do similar. I am currently using an auxiliary 12v 120a alternator but plan to replace it with a 24v 120amp alternator and run a 48v house battery. A 48v Alternator would be an easier solution but are not commonly available yet and very expensive. @ James Yardley

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JohnC avatar image
JohnC answered ·

Hi @James Yardley And welcome.

Not saying this can't be done, but you'd find it quite onerous to do. Eg. You couldn't use the same charger, as each batt (presuming 12V's) has a different 'earth', so need isolated outputs. Then there's balancing them.. too hard.

This is quite an unusual request, so unusual that Victron don't have a product to do this 12 > 48 thing.

Usually road-going applications like the biggest of trucks would use 24V. Do you really need 48V? Maybe you foresee an off-the-shelf Li batt pack?

At 24V, Victron have this new little gem: https://www.victronenergy.com/upload/documents/Datasheet-Orion-Tr-Smart-DC-DC-chargers-isolated-250-400W-EN.pdf

Your future solar charger might impinge on your decision too. There's a big range at 24V, the 48V-capable ones mostly at the high power end.

Sorry to deviate, but need to ask this stuff..



3 comments
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I kind of agree, 12->48v would be unusual. You essentially need an extra 3 chargers if using the 4x converter route.

I'm assuming if you're using 48V its thirsty loads which implies high charging current, and there the 12v becomes a bottleneck.

Not sure about the battery chemistry you're looking at and what you're planning on doing (powering a big winch?), but one option could be to add a 48v alternator (ones used for buses/emergency vehicles), with either an internal or external regulator for charging; need to confirm if you have suitable mounting point and belt for it.

edit: replacing the 12v alternator would mean touching the 12v loads, so that's definitely in the too hard basket.

Hey thanks for the reply...

Ha Second alternator, That's what I figured tonight.

The 48v System has come about because of a specific need for a 2kw heating element, I've wound thee element now and encased ready for a 48v system. The problem is 2kw on 12v just draws an obscene amount of current and the wiring involved is ridiculous.

There's definitely room for a 48v alternator, plus a lot easier to go from 48v to 12v should I decide to add a 'charge starter battery' facility.

Thanks for advice all.

Oh and FYI the 2Kw loading is for quite short durations 10mins max. - the battery bank is LifePo4



Hmmm, Thought that may be the case....