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Tim from Eat Sleep Van avatar image
Tim from Eat Sleep Van asked

RV/VAN 12v alternator to 24v house battery charging

I have a Ford Transit that has it's own 12v battery system with a 60A usable battery output on it. My house battery is a Lithium Ion 6.5Kwh 24v, connected to a MultiPlus 3000VA, with an MPPT controller for the 900W solar panels on the roof. (Also have a BMV700 and CCGX)

It would be great to charge the battery off the vans alternator to get those 700W coming into the battery when I drive. In winter even 900W isn't enough!

The options I can see are:

1) The Victron Buck/Boost 50A device. This would be nice because it can detect the van engine running automatically without having to figure out the vans electrical system (I know it's possible, but this would be easier!). Most expensive option.

2) Use a cheap 12-48V DC converter and then pump that into a separate MPPT controller to charge the battery. Inefficient? But cheap. And nicely isolated from the vans electrical system.

3) Use a cheap 240v inverter and feed that into the MultiPlus charger with a switch to control the input from shorepower to the inverter. I'd have to remember to change the input current everytime I change sources. And not sure it handles <=700W easily, lowest current input possible is 4.5A (1000W @ 230V).

4) Wait to see if a rumoured DC-DC battery charger from Victron would help (seen on another post). Any suggestions?

battery charging
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2 Answers
JohnC avatar image
JohnC answered ·

Hi Tim. Maybe a Victron Orion dc>dc converter, which is adjustable for dc-out. Not the fully fledged charge algorithm, but maybe set for a strongish Float V, and you could relay it in to your engine.

And oh, nice YouTube stuff too. Well done.. :)

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Tim from Eat Sleep Van avatar image Tim from Eat Sleep Van commented ·

Thanks John! I didn't really consider them because their current handling is 20A max (40A input I guess out of the 60A possible). But maybe I could combine a one 10A and a 20A to give the 30A (24v output)

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JohnC avatar image JohnC ♦ Tim from Eat Sleep Van commented ·

Yeh, fair enough. Take care though overpowering whatever that 60A gizmo is. If it's an alternator it may not cough that under some conditions, and if the kit you add isn't controllable you may overdraw on your 12V bank. And if you're just 'topping off' your pv, maybe you don't need much anyway? Only you know your usage patterns/needs though, and familiarity there will be your greatest asset in your choice.

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nebulight avatar image
nebulight answered ·

I would love a Victron DC-DC with VE.Direct like you mentioned in number 4. It's currently the only charge source in my van that the Victron can't see/control. Fingers cross it has VE.Direct and can talk to the Venus!

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