Charging 24v LiFePO4 from bus

[chrisstratton]

I'm looking for a some sort of isolator/converter to charge the house battery (24v) from the bus 12v alternator. Ideas?

[rffffffff]

Look at the victron Orion series chargers. They make a 12v -> 24v charger I think at 360 or 400w that’ll work easily. There are stronger models someplace but a lot more money.

[chrisstratton]

Originally Posted by rffffffff

Look at the victron Orion series chargers.

Thanks. Does this have any protection for the bus (to not drain that system)?

[rffffffff]

You have to look at the specific models but you can run 12v ignition power to some of them so that it turns on only when the bus is running.

[Bert06840]

Do they make 12V to 24V (28V) step-up converters? I did not know that. Also cannot easily find it online.

[dbsoundman]

If you're eventually going to install solar, some solar chargers have the ability to pull power directly from the alternator as a charge source. The Bogart Engineering one I chose is a 30A charge controller, and if you install something like a BlueSea SI-ACR (basically a thingie that senses the alternator charging voltage) and a manual or automatic switch, you can switch between connecting the solar panels to your charge controller or the alternator power source. Hope that makes sense.

[Bert06840]

I don't think that works for the vast majority of MPPT solar charge controllers, or PWM ones for that matter. They are essentially buck converter circuits, which by definition require a higher input voltage than the output voltage.

For PWM circuits that is even more the case, because that's just an "of-off" switch between the panels and the battery.

So putting in 12V and getting 28V-ish voltages requires something else.

Of course there is nothing technical preventing an SCC to be built that can also upconvert (flyback, boost, push-pull, sepic are all topologies that make that possible). Since that is very inefficient on the panels and the wiring, and requires more expensive MOSFETs and magnetic parts that is not commonly done.

As far as I know, there aren't many - if any at all - solar charge controllers that can charge a 28V LFP with much less than 32V at the input.

[dbsoundman]

Originally Posted by Bert06840

I don't think that works for the vast majority of MPPT solar charge controllers, or PWM ones for that matter. They are essentially buck converter circuits, which by definition require a higher input voltage than the output voltage.

For PWM circuits that is even more the case, because that's just an "of-off" switch between the panels and the battery.

So putting in 12V and getting 28V-ish voltages requires something else.

Of course there is nothing technical preventing an SCC to be built that can also upconvert (flyback, boost, push-pull, sepic are all topologies that make that possible). Since that is very inefficient on the panels and the wiring, and requires more expensive MOSFETs and magnetic parts that is not commonly done.

As far as I know, there aren't many - if any at all - solar charge controllers that can charge a 28V LFP with much less than 32V at the input.

I totally forgot OP has a 24v battery system…yeah that would be a problem.