24v to 12v dc to dc converters, how efficient?

[HookEm]

I have the 40A Victron which is enough to cover most everything. That is on a custom ideal diode in parallel with a small lead-acid battery/charger. That way, if anything goes over the limit of the converter - the battery effectively supplies a boost. This required me to trim the converter to be slightly higher voltage than the battery float voltage.

If/when I have to shutdown the 24v battery bank - the little (backup )battery is still enough to pull in the slides, run the water pump, etc.

OK, thanks... But then, of course, you need to charge that 12V Aux battery... How are you doing that (beyond the Alternator)?

 

[HookEm]

I use a 70A victron unit. I have a biggish 37ft fifth wheel and the slides/leveling system all use 12v.
I was using a 40A but a failing house battery murdered it (blown fuses were easy to replace) But I took the opportunity to install the 70A since I wanted bolt terminals instead of the spades on the 40.

So the Victron (Orion) 24/12-70A runs all of your 12V loads. without an Aux (12V) battery in the mix, is that right?
BTW, does the Orion run pretty hot?... Or is it "worry-free" at full load?

 

[willo]

Mine is fine without the aux battery for slides/leveling/etc.

I do have a small SLA on my breakaway brake system. That uses a small charge controller and I just feed it off my 12v converter.
The only time that battery gets used is if the camper tries to run away and the breakaway safety cable pulls the safety switch.

 

[Factory400]

OK, thanks... But then, of course, you need to charge that 12V Aux battery... How are you doing that (beyond the Alternator)?

The aux battery has it's own isolated charger that runs on 120VAC. It is a bit convoluted, but uses the parts I had on hand. It also keeps the little battery tended while the RV (travel trailer) is not being used.