Dear Dave,
We will be living full-time in our motorhome later in 2025 and will be doing a great deal of boondocking. Due to this, we want to have a large solar system installed so we can boondock as long as possible and limit the use of our onboard 10k generator as much as possible.
I have installed a 48V solar system at our off-grid cabin and it has been working fantastically. Believe it or not, the motorhome will have more electrical demands than our cabin does. The motorhome has no propane and is all electric. Three A/Cs, induction cooktop, residential refrigerator, microwave, Aqua-Hot system (diesel and electric), electric fireplace, and electric floor heat.
While I would love to install the solar system myself, I definitely want a professional installer to do this one.
My question is this. Should the system be 12, 24, or 48 volts? I really wanted to go 48 volts, but most installers want to do 12 volts. Other than some limitations on 48-volt components, is there any reason not to go 48 volt? Victron now has 48-volt options and there are very good 48-volt server rack batteries available. Thanks. —Andy, 2019 Tiffin Allegro 45 OPP
Dear Andy,
My initial response was that I know nothing about 48V systems but would try to do some research. This past weekend I had the opportunity to talk with electricity expert Mike Sokol about what was the advantage and challenge of converting to 48V. Mike is my “go to” expert for all things electrical. He had just gotten back from conducting seminars at the Tampa Super Show.
Advantage and disadvantages of using 48V system
Mike indicated that the only advantage of using a 48V system is that you can run voltage through a longer, smaller gauge wire. He did not see any advantage of that in an RV. He also indicated it would be a nightmare to convert an existing unit from the 12V system to 48V due to the complete rewire, step down transformers, and logistics.
All the components that use the house batteries currently are 12V systems, so a transformer would be needed for everything. It would not be easy to convert an existing 12V system to 48V. However, this past weekend I was conducting seminars at the New England RV Show in Boston.
Shortly after I got off the phone with Mike, guess what. An attendee of the Boondocking seminar raised his hand and asked why RV manufacturers don’t use 48V systems! He converted his rig, a 5th wheel, to 48V with 1400 watts of solar power and two 100 Ah 48V lithium batteries! After the seminar he showed me the photos of his setup—it looks like a lunar module! He admitted it would not be a typical DIY project and was very expensive. He boondocks most of the time, has a residential refrigerator and huge power requirements, so it made sense to him.
What other industry experts say about 48V system
So, I asked a few other industry experts.
Here is what I got from Expion 360, which offers a 48V lithium battery:
Here are some of the benefits of going with a 48V system compared with a 12V system:
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- Increased Efficiency: Higher voltage systems generally have lower current for the same power output. This results in reduced energy loss due to heat in wiring, making the system more efficient.
- Less Copper Needed: With lower current levels, you can use smaller gauge wires. This can reduce the weight and cost of the wiring needed in your motorhome.
- Better Performance with Large Loads: A 48V system can handle higher power loads more effectively, which can be beneficial for appliances that require more power, such as inverter systems or large battery banks.
- Scalability: As your power needs grow, it’s easier to scale a 48V system. You can add more batteries or solar panels without needing to upgrade wiring or infrastructure significantly.
- Compatibility with Renewable Energy Systems: Many solar charge controllers and inverters are available for 48V systems, making it easier to integrate with renewable energy sources.
- Less Voltage Drop: In longer wiring runs, a higher voltage system will experience less voltage drop, ensuring that your appliances receive sufficient power even over extended distances.
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Customers will still need a 12V converter to run 12V loads such as lights and other 12V components, but a lot of the 48V inverters have a 12V converter built into them, otherwise a 12V converter can be installed to satisfy those needs.
This sounds like they are “pro” 48V?
Another opinion on 48-volt system
However, when I asked my “go to” electrical technician from Progressive Dynamics, he agreed with Mike. Here is what he sent:
Possible yes, practical no. I agree with Mike on this.
First off, all of the DC accessories in the RV are designed for 12 volts. Simply adding a 48-volt battery would destroy all the 12-volt components in the RV.
This means additional equipment will be needed to bring the 48 volts to 12 volts in the RV. This would require a DC – DC converter with 12-volt output and enough current to power the RV components. The inverter would have to operate at 48 volts and a charger would have to provide 48 volts. Any installer should be well-versed in performing a conversion like this.
I’ve been told by some customers that a 24- or 48-volt system works better and the wire gauge is smaller (less expensive).
Any time you change from one electrical value/type to another power is wasted through heat. When you’re boondocking, any additional power conversions are wasting valuable battery reserves.
Are you saving money? That would require a full evaluation of components and usage.
Back to Dave
So, it seems most agree that it is a good system—it just needs to be engineered into the build. Until the market perception shifts, we are stuck with 12V.
I would love to hear what our readers think or what they have done for upgrades.
You might also enjoy this from Dave
Can different type and age RV batteries be mixed? Can I add a lithium battery?
Dear Dave,
Did you answer a question recently about mixing batteries of different sizes, chemistry and age? I believe it was you but I can’t find it in the RVtravel.com archives. —Ed, 2005 Holiday Rambler Ambassador
[NOTE: This is actually a two-part question. Ed sent the first question listed above, and after I sent the rough draft to him, he sent a follow-up on how he added a third lithium battery two years later. That question and response are added to the bottom.]
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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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Sounds like a difficult, expensive undertaking. Have a new coach with 48 system to start.
Excellent article, Dave. 48 volts sounds like good idea, but as Tom below says, you would have to have your build (trailer OR motorhome) engineered at 48 volts from the ground up.
Just curious. Why would the coach have to be 48v from the ground up. Replacing 6v batteries with 48v batteries. Replacing 12v inverter with a 48v inverter. Both inverters output is 120v. No difference in the output voltage. Only how the energy is stored and changed to 120v.
I would think (perhaps incorrectly) that if you want your rig to run off a 48 volt system, everything would have to run off 48 volts. I was thinking all the 48 volt stuff coming from the factory would be cheaper than converting everything over to 48 volts. I have zero experience with 24 or 48 volt systems so maybe my ignorance was showing. Not the first time . . . Thanks for pointing out some 48 volt info.
I believe Aeon RV is employing a 48v system with a converter to 12v for lights, water pump, etc. I checked it out at a local outdoors show and it didn’t seem that complicated. More investigation…
A 48v to 12v converter is added to the system to run all 12v coach resources. Not difficult at all.
There is no benefit of converting to 48 volts for an RV. Higher voltage doesn’t increase capacity, extend reliability or reduce costs. It just requires less amperage for the same load (V=I/R).
Batteries store energy, they don’t make energy so to run the generator less, one either uses less power to replenish or they’ll need to recharge from an alternative source like solar, wind or alternator.
Converting to LifePo4 can decrease charge time (generator run time) via their ability to take higher amperage. Increasing amp hour capacity merely increases time between charges but does nothing to reduce time required to charge. Increasing voltage decreases amperage but that’s it….
There are both benefits and costs.
How they balance out depends on one’s situation and preferences.
This is system engineering.
I respectfully disagree John. Generator run time is contingent on battery depletion, not rated system voltage.
A 48V battery will discharge at an identical rate as a 12V battery but just at lower amperage. System engineering is bound to Ohm’s Law (V=I/R) my friend.
Even if we gave him a 10,000 watt inverter to run in lieu of his generator, the only thing we’re changing when we change DC input voltage is the amperage and cable feeding the inverter, not the ability to boondock with less use of Genny.
TLDR: Four 100Ah batteries will provide 400 amp hours whether they’re wired in parallel at 12 volts or in series and 48 volts.
There are pros and cons, and how these balance out depends on your situation.
Start by making a spreadsheet with columns for 12 volts, 24 volts, and 48 volts.
This will show how benefits in one area are offset by costs in another area.
For example, thinner cabling vs. having to down convert to 12 volts for lighting, furnace, water pump, etc.
As others have said, it depends. Both have compelling advantages and disadvantages. In the OP’s case, it sounds like they will have fairly heavy AC requirements. A 48V inverter system is much more efficient for those kind of loads than a 12V system. It will run cooler and quieter with less power wasted.
DC/DC down converting from 48 to 12V to run the DC house loads isn’t that difficult although you will find more converters for 24V to 12V THAN 48V. Figure out your AC loads vs DC loads and go from there.
My question is has Andy calculated the current draw of all the electrical devices he has, cook top, refrigerator,, floor heater. How many server rack batteries will he need to power those components and the weight factor. Server rack batteries are 100 pounds minimum. Can he install enough solar to maintain a charge.
Hi Wallace. Short answer is yes to all questions. I’ve done extensive research on power needs using usage monitors and calculating times we would be using all components of the RV. While the server rack batteries are 100 pounds, they would actually have less weight than a typical 24v sealed LiFePO batteries to get the same total kilowatt hours.
If you want to run 2 AC units, and/or electric stove/oven components, and you are full timing, I think it makes sense. Then you can use the existing low voltage DC cabling to carry current to the inverter. I believe the folks doing it are keeping and existing, smaller capacity 12V system for the 12V components so you don’t need to convert from 48V DC to 12V DC.
And in a new twist, consider changing the 12V starting battery over to LiFePO4 and combining the house 12V DC off of that. Capacity needs to be considered and choice of batteries (See Ionic brand for a 3000CCA rated starting battery). A good design might end up with separate 12V house and starting circuits at least during crank.
The CONs of course are: 1) Even if you find someone competent to engineer and implement it, you may need someone to repair it away from the installer site. If I were not technically inclined and did not understand the system well enough to DIY maintenance and repair, I would not take that risk. 2) $$$$
If you haven’t found it, Mike Maas has a video about his 51/12V dual system conversion. It is short on enough technical details to be able to use as a design guide.
Great video! I hadn’t seen this one, but it is a good synopsis of many of the other videos I’ve seen.
Thanks!
Thanks for the informative information Dave! I think 48v solar systems are still very new for RV’s. Most everyone uses either 24v or stays with 12v.
I think 12v does have performance and growth issues. 24v a little less. 48v even less.
Victron didn’t have many 48v inverters for RV’s, but now does have a couple. Most of the off-grid systems for cabins and residential use, always use 48v because of the cost per watt hour being less and systems are easily expandable.
My guess is that in another few years, we will start to see installers doing more 48v installs in RVs, but only time will tell.
Thanks again for the research and feedback.
LiFePo Battery considerations:
BB battery 12v/270Ah, 3.24Kwh, 81lb, $2,149 = $0.6634/wh
Victron 12.8v/330Ah, 4.22kwh, 64lb, $1,749 = $0.4141/wh
EG4 51.2V (48V server rack), 100ah, 5.12kWh, 100lb, $1,199 = $0.2341/wh
So, the biggest cost savings is in the energy storage.
A 12v, 24v, and 48v intervters all put out 120v.
The matching of batteries to inverters is the biggest initial engineering concern.
Thank you, Dave! I have seen a YouTube video or two recounting the merits of a 48-volt electrical system in all-electric diesel.pushers. I will leave it to the creators to try to convince you of the merits of the conversion.
https://youtu.be/CFg-ZfNS4n8?feature=shared
https://youtu.be/ixFFa4wqZDM?feature=shared
We fail to boondock enough to consider a 48-volt system, but we do plan to consider going to Master Tech in Elkhart to get Lithionics lithium iron batteries when we replace our AGM house batteries. Have a great day and safe travels!
I completely disagree with Dave’s answer on the 48v vrs 12 volt battery swap. He did not listen to what the person asking the question said. Are the 3 a/c units 12 volts. Is the residential frig 12 volts. Is the induction cooktop 12 volts and what about the microwave? He is converting the 12 volts to 120 volts. The 48 volt system would be way more efficient for this purpose. As for the 12 volt systems in the unit. What is voltage output of the 10k generator? Convert tor 48v DC to 120 AC and feed the input to the generator circuit. Manufacturers won’t do it because it’s to expensive.
What about separate 48v and 12v systems? Use the 48 to convert to 120 and a smaller simpler 12 volt system for the 12 volt side of the rig. The two systems are already run by separate panels, why mix them since it seems that is one of the main problems.