stevelex avatar image

12v car battery charging 24v house battery - confirming my choice.

This question has been asked, but I've read through the threads and have not found the answer I need.

I have a 24v house battery for my cargo van conversion.

Everything is designed and set up (I've done a 12v system before) without alternator charging.

I would like to add on alternator charging.

My alternator (GMC Savanna, 135 amps I believe) is 12v and my house batteries are 24v. (I can buy a new alternator that goes to 240amps and I may do that).

Is this the right product?

Victron Energy Orion-Tr Smart 12/24-Volt15 amp 360-Watt DC-DC Charger, Isolated (Bluetooth)

Is there one with greater amps output?(I could not find anything).


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1 Answer
Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

Hi @stevelex, welcome to the Community!

The Orion-Tr Smart 12/24-15A is definitely the correct product, yes. Please be certain of the seller from whom you're purchasing it, however, as after-sale technical support, questions, and/or warranty issues will all be handled directly by the authorized Victron distributor from whom you purchase any Victron product.

There are not, at this time, any higher-output current models available in your selected voltages; given that the Orion-Tr Smart charger uses passive convective cooling to decrease noise and footprint while increasing overall efficiency, a limitation of that is that unfortunately there's only so much current that the unit can handle before you have to start looking at cooling fans and big cases and all of that, which would then be an entirely different product.

I will note a couple of things: In order to deliver ~15A of current to your 24v target battery, this unit will need to pull ~34-50A (that latter being under possible surge conditions, overall continuous would tend to be on the ~34A side) from your source battery (starter battery) so please ensure that your alternator is capable of continuous output current of ~34A + your total chassis loads. Long story short: please make sure you have at least a 100A alternator or better to make sure that you're not overloading/overheating it.

I will also note that you probably don't need the isolated version - so long as both your battery banks are sharing a common negative return path (read: chassis grounded) then you can use the non-isolated version, which would save you a bit of cash on the purchase. That being said, the non-isolated Orion-Tr Smart chargers can be difficult to come by sometimes, so the isolated version may be all you can find at the moment... in which case, even if your batteries are sharing a common negative return path, you can still use the isolated version.

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Well, that's a complete and total answer. I think my current alternator is 145amps but it might be 105. If the latter I can buy a bigger one on Amazon and I will probably do that before hitting the road.

I also got a pretty good response by email from Victron which basically said the same thing you are saying about total draw on the alternator.