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Ben2022

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Mar 9, 2022
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Is there a way to use a server rack 48v battery with my existing 12v RV setup WITHOUT buying a whole new inverter? I know there are step downs to handle the trailer 12v but I don’t think those are heavy duty enough to handle inverter loads are they? I’m looking to switch to lithium and like the simplicity of the server rack batteries but don’t know if I can justify the cost of the battery and a new inverter.

Current system: EpEver solar controller 100A model
900w of solar.
6 Trojan 6v batteries wired for 12v.
AIMS 4000w 12v inverter charger

Thanks
 
In theory I guess you could use a DC to DC to DC converter, but I know of no 48 volt to 12 volt converter Of any significant power.

I use a 70 amp 24 volt to 12 volt DC converter to power my trailer leveling system. That can be stacked 3 in parallel for a total of 210 amps, but this is not even enough to power a 300 amp inverter, and those converters would cost $450 for three, and an inverter that would provide any real power would cost less Than those converters.
 
So the next question would be is there any benefit to the expense of changing my whole configuration to 48v (given that system voltage is 12v) or just buy a 300 or 400 ah 12v lithium? (Chinns or ampeare time) The whole thought process I had behind the rack battery was build quality and built in features but I guess I don’t NEED those extra features.
 
Ben2022 said:
So the next question would be is there any benefit to the expense of changing my whole configuration to 48v (given that system voltage is 12v) or just buy a 300 or 400 ah 12v lithium? (Chinns or ampeare time) The whole thought process I had behind the rack battery was build quality and built in features but I guess I don’t NEED those extra features.
Click to expand...
IMHO, there is not a clear answer to this.
48V systems are nice because they *tend* to run more efficiently.
48V Systems are nice because you can use smaller wires and in a tight space, this can be a bigger deal than some give it credit for.

HOWEVER:
  • It is easy to find 12V appliances for the RV. It is a little harder to find 24V appliances. It is difficult to find 48V appliances.
  • The selection of 48V-12V DC-DC chargers for use with Alternator charging is very limited and very expensive
  • The selection of 48V-12V DC-DC converters for running appliances is limited..... particularly if a low-voltage disconnect is desired.
  • If a large percentage of the power usage is going to be from 12V devices, the power loss of converting from 48V can significantly offset the efficiency gains of using 48V.
Costing can be all over the place. To determine which is most cost-effective you pretty much have to design both a 12V and a 48V system that meets the needs and then check the pricing to determine what is better.
 
FilterGuy said:
IMHO, there is not a clear answer to this.
48V systems are nice because they *tend* to run more efficiently.
48V Systems are nice because you can use smaller wires and in a tight space, this can be a bigger deal than some give it credit for.

HOWEVER:
  • It is easy to find 12V appliances for the RV. It is a little harder to find 24V appliances. It is difficult to find 48V appliances.
  • The selection of 48V-12V DC-DC chargers for use with Alternator charging is very limited and very expensive
  • The selection of 48V-12V DC-DC converters for running appliances is limited..... particularly if a low-voltage disconnect is desired.
  • If a large percentage of the power usage is going to be from 12V devices, the power loss of converting from 48V can significantly offset the efficiency gains of using 48V.
Costing can be all over the place. To determine which is most cost-effective you pretty much have to design both a 12V and a 48V system that meets the needs and then check the pricing to determine what is better.
Click to expand...
So it’s sounding like any efficiencies gained wouldn’t be worth it. Wiring isn’t a consideration since the 12v system is already in place with proper sized cable. Looks like a straight swap to a 12v lithium is the cheapest option for me.
 
Ben2022 said:
So it’s sounding like any efficiencies gained wouldn’t be worth it. Wiring isn’t a consideration since the 12v system is already in place with proper sized cable. Looks like a straight swap to a 12v lithium is the cheapest option for me.
Click to expand...
There is a little bit of gain here, losing 6 golf cart batteries and gaining 2x 12v lithium (or 1) will recoup a bit of space. Also, going to lithium, don't forget to upgrade your battery bank/inverter fuse(s) to class-t.
 
How much 12VDC current do you need? You can buy buck converters. Powering each device independently isn't the worst way to go if you only have a few things to power.
 
Automotive OEMs and parts suppliers (Bosch) etc are making the shift from 12V to 48V for a host of cost and efficiency reasons. RV chassis OEM's should eventually shift to 48V DC systems, but change comes slowly to this vehicle sub-sector. The RV community is hostage to "old" 12V alternator/battery combo that forces many RV appliances to be 12V. Right now, 48V appliances (fridge/fan/HVAC/pump) are low-volume and relatively expensive. What is needed is a RV/marine/offgrid appliance industry shift to 48V products, which would align with now-widespread 48V LFP battery technology.
 
lucariffer said:
but change comes slowly to this vehicle sub-sector.
Click to expand...
That is an understatement. I have been hearing about a shift to higher voltages in the auto industry for well over a decade.....but it ain't happened yet.

At one time, one of the arguments was that higher voltage lightbulbs had thicker elements and could handle the vibration better. I doubted that was an issue 10 years ago and it is clearly not an issue with the advent of LEDs.

I hope you are right that the demand due to 48V batteries will accelerate the change..... but I am not holding my breath.
 
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