Rv 48v to 13.6 converter newbe question

[Jason flores]

I want to power my rv distribution panel from my 48v 305ah batteries with a 48v to 13.6 buck converter I don't want the stock converter/charger charging the 12v stock system batteries (2 lead scid 200ah) .my issue is where my 48v battery is located is 50ft away from rv in a shipping container . I looked up a 305ah battery is 150a correct ?
The buck converter I'm using is 20amp (for lights ,fan , blower , etc ) I decided I want to run the 48v 50ft to the rv instead of putting buck converter at beginning of run for 13.6v 50ft becuase wire size .my question is do I rate my wire to what's being used 20a (20a buck converter) or to the 150a 48v could produce ?
I surely don't want to run 13.6v 50ft of 4/0.
Or 2/0 for 150a

Thank you sorry for newbe question

 

[Dooug]

Are you running an inverter off the 48v? Would be easiest to buy a good 120/12v charger and run it off the inverter.

To run the buck converter you just need to run heavy enough wire for the buck converter at the 48v side and fuse it appropriately. Math following...

20amps @ 13.6 volts is 272 watts. Divide that to 272 watts by 48 volts and you get 5.6 amps. 10 gauge can easily handle 50 feet with a 2% voltage drop. 12 gauge would handle 10 amps with 3.3% voltage drop. This leaves some headroom incase your converter pulls a couple extra amps.

Someone double check my math?

 

[Jason flores]

Are you running an inverter off the 48v? Would be easiest to buy a good 120/12v charger and run it off the inverter.

To run the buck converter you just need to run heavy enough wire for the buck converter at the 48v side and fuse it appropriately. Math following...

20amps @ 13.6 volts is 272 watts. Divide that to 272 watts by 48 volts and you get 5.6 amps. 10 gauge can easily handle 50 feet with a 2% voltage drop. 12 gauge would handle 10 amps with 3.3% voltage drop. This leaves some headroom incase your converter pulls a couple extra amps.

Someone double check my math?

The problem is there's a loss when going from DC 48 to AC 120v back to DC12v. So I'm running a line from 48v DC 50ft to 12v buck converter .
I have 9000watts array to charge pretty quick I'm thinking it won't phase the 48v syatem all the lights are led 4watt a piece (10 total) slides outs only 1 time (not sure on watts) and furnace fan is 12v (not sure how much it pulls ) everything else will run off the 6000xl 240v inverter ..

 

[Vigo]

Both approaches have some loss. I think the DC>AC>DC conversion losses would not be much worse than the losses from voltage drop if you did the wiring in 48vdc, plus you can get the regular extension cord necessary for under <$20. If you have to run a pair of 10ga wire 50+ ft i think you'd be hard pressed to not spend more than that. But it's really up to your preference as its a pretty small circuit either way so the losses would be easily 'afforded' by your 9000w system.

 

[Jason flores]

Both approaches have some loss. I think the DC>AC>DC conversion losses would not be much worse than the losses from voltage drop if you did the wiring in 48vdc, plus you can get the regular extension cord necessary for under <$20. If you have to run a pair of 10ga wire 50+ ft i think you'd be hard pressed to not spend more than that. But it's really up to your preference as its a pretty small circuit either way so the losses would be easily 'afforded' by your 9000w system.

Thank you
I was looking up wire calculators. And for 48v 30a for 100 foot (50 ft pos /neg ) explorer life on youtube states you must use both in distance measurements ?
It says 4 guage wire going 48v to trailer then buck converter to 12v 150$ in wire ( loss of 3%)
It says 2/0 if 12v from start (converter at 48v battery) then go 50 ft to trailer 350$ same loss of 3% So if that's the case it's alot cheaper to run 48v to trailer then convert.

My 120v to 12v charger / converter that came with the travel trailer was pulling a continuous 300 watts (on watt o meter) its a 120v plug into back of panel I'm gonna simply unplug it as ill have no use for it while off grid at the property.
When I go back to shore power at rv park I'll plug it in ..