Question Converting my RV 12V to a 48V system for LiFePO4?

[Neal]

I hear discussions of 48V systems and how it's better, etc. Take my coach for example that has a Magnum 2812, right now lead-acid batteries which I'm changing to LiFePO4. What is involved in a 48V conversion and also help educate me and others on the benefits of this change.

 

[jaydee325]

Sounds like a major redesign of the low voltage system.

Here is but one example of what may need to be changed out. USB outlets. I'm guessing they are looking for 12VDC in to step down to 5VDC. If the new inverter does not provide 12VDC out to tie into exiting equipment looking for 12VDC, you'll be changing a lot of components.

There are many LiFePO conversations out there that stay 12V. Why endure the additional expense to reinvent the wheel?

Also, is this your forever coach? What is the expected payback ($) on such a mod?

 

[TheLooks]

48 volts stays in the solar/charging system. It is more efficient and allows the use of smaller wires. High voltage, lower amps. It has nothing to do with what is delivered to the coach devices. It is how you hook up the the batteries to pull the 12v. Or use a device that takes in 48 and puts out 12. Many people hook up their panels to put out much higher voltage and the charge controller reduces it to 24 or 36 or 48. Or 12.

 

[Rich W.]

In an RV 48 volts is all about running an air conditioner (or two) because feeding a 48v inverter requires 1/4 of the amperage of a 12v system to make the same AC power. It still requires a big battery bank which has been made feasible these days with lithium batteries, but at a significant cost.

But it comes with other complications and costs. You would also need a DC-DC converter to get back to 12v (because you would no longer have a big 12v battery bank), and it would have to be fairly robust to power the systems that draw higher amps (jacks, slides etc). You would also have to re-wire your breaker panels so the inverter powers the air conditioner(s) - not a big deal but another chore. And of course there’s the cost of the new inverter/charger and depending on what you now have, new solar charge controllers. Also since you have 12v panels, you’d have to re-configure your array to feed 48v to your MPPT(s).

But if you’re not going to invest in a big battery bank and run an air conditioner (or two), 48v doesn’t seem to have any advantage, other than greater efficiency, but that benefit seems nominal in this application. And since you’re converting to lithium anyway, you could still have the rest as a future goal and approach the project incrementally.

 

[Joe Hogan]

If you are looking for Techs familiar with 48v RV systems, we might take a trip to Elkhart when at the Mother ship.

 

[Kevin D Pem]

The main advantage is system efficiency! Stepping up or down in voltage, power takes a hit. An inverter intrinsic load is still figured in watts, so although the amperage to drive the circuit is lower, the wattage stays the same. Yup the advantage is in efficiency!

Disadvantages include the requirement of a 48 volt bank. One battery failure and you will have to replace it to use the other 3. Depending on age/use it may require that all 4 would need replacement(assuming you are using 12v batteries). Cabins and off grid houses, 48volts is the norm, that is likely because you have a battery house,and asizeable battery investment I might add. A 12 or 24 volt system with the same number of batteries offers redundancy.

If you were considering a larger solar array the positive point would be 4 times the number of panels to the same size of controller. My 24 volt system requires 3 controllers and with the same size controller I would only need 1. However that would not be an option due to panel Shading issues. A 12v system of same controllers and I would need 6 controllers.

One more thing!!! Not all lithium batteries can be series connected, it depends on the BMS used in the battery.

In conclusion, I determined a 24volt system was ideal for most RV systems due to the portability issues. The need for free space, and battery requirements.