48 volt battery to 12 volt system

[DonTom]

I can see the BIG advantage in very high current stuff (such as EV motors), to have a higher voltage, but not that big of an advantage to bother with it in an RV, IMO.

However, it looks like we're saying they screwed up in the beginning to make 12V the standard. 12V has no advantage that I can think of other than it's in very common use already. OTOH, it's just not worth changing over in our 12V world.

But if E-RVs ever become common, it might not be a bad idea to have everything in it run from 380 VDC or whatever and not need to convert anything--and no need for a genny with enough KWHs in the battery. No inverter, no genny, no converter (but an EV charger), no solar etc. Just run everything from the ~750 KWH battery!

-Don- Van Horn, TX

 

[strugglebus]

I would think that CA new standards for EV items would push for more efficiency in all motorized vehicles, gas or electric. Looks like lead acid batteries have a limited lifespan. They had a great run but they just aren't the future. Need energy storage to get off the fossil fuels. That also means less energy loss coming out of that storage system. I'm just trying to keep slightly ahead of the curve, money allowing.

 

[DonTom]

I would think that CA new standards for EV items would push for more efficiency in all motorized vehicles, gas or electric.

Yep. And the day will come when we can run two air conditioners direct from the battery all-day long and not even notice any difference in the battery SOC.

But I doubt I will be alive to see it happen.

-Don- Fabens, TX

 

[John From Detroit]

Solar controllers only work with sources like a solar panel that produces constant current regardless of the output voltage. You'll likely burn it up if you feed it from something like a battery with virtually unlimited short circuit current.

Thanks. as I said or at least implied "Would it work?" I did not know.

 

[Old_Crow]

Yep. And the day will come when we can run two air conditioners direct from the battery all-day long and not even notice any difference in the battery SOC.

But I doubt I will be alive to see it happen.

-Don- Fabens, TX

I was watching a show the other day where they drove a Tesla around a track for like 8 miles and measured battery consumption. Then they did another run with just the heater on, then again with just the a/c on. Of course, the run with the heater used more battery, but surprisingly, the run with the a/c used almost exactly the same as the run with no climate control at all. They also tested regenerative braking vs. normal 2 pedal operation. As expected the regen braking used less battery for the run.

 

[Minnichds]

Thank you for posting everyone. I just purchased a camper and want to set it up for off grid as well. I was leaning towards 48V because of the wiring but wasn’t sure about setting up a separate circuit for AC run off the 48 VDC battery bank or just tying into the old 12v system. If anyone has done this I would love photos, ideas, recommendations, wiring diagrams etc.

My goal is to be able to park my trailer in an area for maybe a week and have the ability to keep the fridge cold and maybe cool it down at night during summer occasionally. I think I’m looking for a 3500W sine inverter with a bank of 48VDC x 200A. I’d like it to charge when I’m driving and with shore power, wouldn’t be hard. I can tie in solar later. My water heater and fridge both run off propane so it’s really the AC and outlets that will be using the bank.

 

[Ray-IN]

A man on escapees.com is doing exactly that now with his 5th wheel trailer.

 

[DaveM452]

I'm planning my 48V Conversion Plan for my Trailer. I plan on using a 48V Hybrid Inverter/Charger/Solar Controller with a 48V 100Ah LiFePO4 battery. I'd like to eliminate my 12 house batter and the Converter/Charger that keeps it topped off. I found a 48V to 12V step down converter that will supply up to 60Amps at 12V. My converter/charger is only a 55A unit. I can't see a drawback here. On shore power I don't care about any no load current or 48V to 12V losses. Am I missing something?

 

[John From Detroit]

You will need a buck converter for your 12 volt stuff. This is a device that either simply reduces the voltage. Like a pressure regulator on a water line (Rather not efficient) or a "Switching power supply" that chops the DC into square wave or more precice retangular wave AC (Zero to 48 volts) then charges big filter up to 13.6 volts.. the with of the retangle depends on the current draw... These are efficient and work well. IN fact this is how many modern electronic power supplies work.
I'm not going to suggest one as I don't know where to find high current (mroe than 3 amps)( versiosn.

 

[Ernie n Tara]

Note that those propane devices typically require 12 Vdc as well for control purposes.

Ernie