Charging 24v RV house system from 12v battery/alternator

[bcarpman]

So I have a fully functioning 24v system in my RV. 1000w solar, 4.8kwh lifepo4 battery bank, MPP Solar LV2424 inverter/charge controller. It all works great.

However, despite a lot of peoples assertions that I should never want to charge the batteries off the alternator, there are times when I'm driving at night or in bad weather, after boondocking for a couple days, that it sure would be nice to charge up the batteries a bit as I drive. I didn't think this task would be as complicated as it is. The problem is current limiting the charging.

I purchased a couple of adjustable 12v to 24v solutions that say they have current limiting, but none really do. I'm smart enough to add a fuse inline a little over maximum current draw, and all of them blow fuses within a couple seconds to a minute. If I risk it and run without the external fuse, within a minute the device "lets all the smoke out"

My latest attempt was a Victron Energy Orion 12/24-10 DC-DC Converter. I figured this has to work. Hey, it's a Victron and it states it's made for battery charging. Nope, that sucker would pull as much current as it could get until it fried itself.

Can anyone recommend a current limited solution to taking 10-30amps of charging while I'm driving?

 

[erik.calco]

Will has old videos where he discusses this. I remember him saying it was bad for your alternator.

His recommendation is that you get a 2nd alternator for this purpose. You can have one installed. I forgot what type. There is a common application that does this, but I can't remember what it was.

I don't remember him talking about current being the issue, though. So not sure if that solves your problem. But, it's worth looking into if you haven't ruled it out already.

 

[bcarpman]

Will has old videos where he discusses this. I remember him saying it was bad for your alternator.

His recommendation is that you get a 2nd alternator for this purpose. You can have one installed. I forgot what type. There is a common application that does this, but I can't remember what it was.

I don't remember him talking about current being the issue, though. So not sure if that solves your problem. But, it's worth looking into if you haven't ruled it out already.

Yes, current is the issue, even when talking about 12v to 12v (which is what Will's video was about). with 12v to 24v current limiting is a given.

 

[erik.calco]

Wind power addresses it with a sink. But that is probably overkill for your need. IDK how that works and ruled out wind power before I could find out.

They are also probably handling it while it is still AC, which won't help you if you are addressing it on the DC side.

@JeepHammer is an expert at alternators, though. He can probably help.