Converting a Diesel Pusher to ALL Electric.
Converting a Diesel Pusher to ALL Electric. Well, except the main engine. :D
I am remodeling our coach. Part of the remodel is redoing the 29 year old house electrical system. Or, you might even say, replacing the system.
I am currently in the design phase, and am learning as I go, so please be gentle. :flowers:
Here are some parts of the plan:
Replace propane fridge with 110V residential unit.
Replace the propane water heater with a 110V electric unit.
Remove ALL propane systems.
Add 24V radiant floor heating.
Replace FLA batteries with LiFeP04 batteries in a 24VDC configuration.
Replace the separate MSW inverter, charger, and ATS with a Victron Inverter/Charger (possibly 24V/3000W?)
Remove original 100W solar panel on roof and add more modern panels.
Add all of the necessary wiring, controls, monitors, etc. as needed for the wiring. (Leaning toward Victron components.)
Rewire the 110V so the two (2) roof heatpump units can be powered by the inverter(s).
Here is one piece of the puzzle that has me stymied. If I was installing 12VDC system, I could charge the house FLA (or AGM) batteries with the main engine alternator while driving. I have read that with lithium batteries, since they can take a high amperage charge, it is very wise to install a DC-DC (buck converter?) unit to limit the amount of current so the alternator does not overheat and self-destruct.
Is there such a unit that can limit the current and also step up the alternator's 12VDC to 24VDC to charge the 24VDC battery bank? Is called this a "buck-boost converter"?
Also, is this recommended? Or, should I rely on solar, generator, and/or shore power only to charge the house batteries and forego connecting the alternator output to the house system?
Thanks to paul65k and astrocamper for their descriptions of their systems. Both have been very helpful. :bow::bow:
All I can say is WOW!
Running 2 AC/ heat pumps and radiant floor heat via 12 or 24 volts will require some batty bank!
You don't mention a generator? Or how you will power 120V water heater? If you travel most days a large engine Alt can be a help but what about days not traveling?
You don't mention climates you intend to travel / stay but did mention heat & AC both of which can be a BIG load for Betty's.
I'd suggest an energy estimate & energy balance for all systems as a starting point.
You're asking for quite a bit out of your system, and you will need quite the battery bank to run it. And solar bank.
Check out this YouTube channel: https://www.youtube.com/channel/UC-x...RrOTE_74WbU5cg
It's a bus conversion, but the owners are doing exactly what you're describing. When you see the amount of solar they've installed to run the system, I suspect you'll realize it may not be as good of an idea. And, when you see the rack system they have to double their solar capacity, realize that they've just added two additional ground-deployed panels to augment the ones on the roof.
A few suggestions:
1 - Easiest way to charge your 24-volt house batteries while on the road might be to install a 24-volt high output truck alternator to your main engine. If you get one with the correct output, you might be able to run it directly to your battery bank for charging. If not, then a DC-to-DC charger would make it work. You might also be able to use it through your solar charge controller to charge the house batteries by running the output from the 24-volt alternator parallel to your solar bank into the charge controller.
2 - Consider using a diesel heater instead of all electric. Even the high-end coaches being sold which claim to be 'all electric' often use diesel heat. There's not a really good way to heat a coach off batteries for a length of time, and you don't want to leave yourself with frozen pipes should you encounter a stretch of overcast freezing weather.
3 - Redundancy is important. Even if you go with 24-volt heat, you will benefit from having a redundant heat source. Again, a week of cold cloudy weather will make you wish you had something other than solar to rely on for heat.
4 - You can get an electric water heater which also has a loop for running a coolant line through it. That allows you to make hot water from the engine heat or from something like a Webasto (diesel heater).
5 - After you watch the YouTube videos I linked to above to see the size of their solar bank, measure the roof of your coach and determine just how many watts you can safely put up there. This will largely determine much of the plan you are doing. It makes no difference how big your battery bank is if you don't have enough solar to recharge it in the time the sun shines.
6 - Do you math on hours of sun where & when you plan to be with the coach. If you are in the northern part of the country or traveling in the winter months, you're solar output will be reduced from the stated output on the panels.
It seems to me that a hybrid system is going to be the best path moving forward on this kind of thing. Relying on just one energy source leaves one open to problems. Propane has its advantages in heating a coach, but a diesel heater can replace it easily. That leaves you with only a single fuel to have to refill.
Hope this helps. Looks like a fun project.
To charge a 24v lithium from your 12v alternator- look at Victron’s Orion Dc-Dc charger. It can charge the lithium’s with the proper voltage & cutoffs.
How large of a lithium system are you thinking about? & how large of solar?
Good luck with your project
Thanks for all of the comments and suggestions thus far. :bow::bow::bow:
Yes, there is a diesel generator on-board. It is a 7kW Onan. Yes, Redundancy is Important. We plan to be self-sufficient (not connected with a cord) with two electric sources: solar and genny.
I did a preliminary energy audit. Not everything will be intended to run for days without running the genny or good sunshine during extremely hot or extremely cold days. The size of the battery banks and the solar would probably be unrealistic. :blink:
Some genny use is most likely expected for extra hot, sunny days when both A/C units are needed. Now that the basic decisions on power sources have been made, I need to conduct a detailed audit to determine actual components, number of panels, batteries, etc. Then, I will review my decisions again.
Water heater will probably be a 110V, 10 gallon, residential type unit. I will need to be able to drain, flush, and bypass the heater tank in case I need to winterize the coach. It may live where the original RV gas/electric heater was. Not sure yet. I would like it closer to the kitchen. Maybe in the basement where the existing gas furnaces live?
I considered adding a diesel heating system (like Aquahot or Webasto), but am still leaning toward using the heatpumps and electric radiant floor heating. And, adding some heat pads for the fresh water and waste tanks.
Additional insulation on the walls and ceiling is part of the plan to decrease the load on the heating and cooling systems.
With LiFeP04 batteries, the recharge time is much, much less than FLA or AGM. If the genny does need to be run to recharge the batteries, it will only be for an hour or two instead of possibly 6-8 hours. There are many more beneficial characteristics of LiFeP04 that make this plan feasible as well. Too many details to list here.
Thanks for the pointer to that bus remodel. They recorded a LOT of information. It will take me quite some time to review. I did see something about them using a Tesla battery. I have seen some other videos about this. I don't think I want to go that route. But, it will be interesting to learn the what's and why's.
We are not sure about where the coach may be used, but we are not planning on using it for ski trips or other winter activities. I've shoveled enough snow earlier in my lifetime, and I do not any more practice shoveling the white stuff! :nonono:
Comments are very much appreciated. A link to our coach efforts are in my signature below, if anyone is interested. It contains notes from when we purchased the coach a few years ago, including what repairs were needed along the way. It is very much a work in progress. :rolleyes:
If you're doing such a retrofit, you should ditch the rooftop ACs while you're at it and replace them with mini-splits. Mine do a better job cooling (and heating, since the heat pumps work well down to the single digits) and use a third of the energy of the rooftop units they replaced. This also addresses the heat pumps you want to add, and removing them frees up additional space for solar panels, assuming you aren't already planning a raised rack to house them.
Most residential style water heater tanks are coated in ceramic or porcelain to deter rust, using one in an RV is recipe for disaster. Just stick with a simple RV water heater, and either buy one that runs on electric out of the box, or buy a 110V heater that screws into the anode port.
A pair of Victron 24/3000/70 inverters will charge the batteries at ~4kW. That means to fill a 20kWh bank discharged to 20% SoC, you will need to run your generator at least four hours - LiFePO4 banks can charge quickly, but there are other limiting factors you need to remain aware of, especially if chasing high elevation with a N/A genset (though the output of a 7K Onan at 10K' is still more than the charge rate of the mentioned pair of Victrons). If you go with a single Victron, charging will take twice as long.
I think you're on the right track avoiding Tesla or used EV cells, in general. LiFePO4 is a relatively benign chemistry and much safer for RV use.
If you go with new, name brand components you're looking at north of $20K for solar, batteries, and supporting equipment alone - assuming you don't cut corners.
OMG is as polite as I can be without getting in trouble with the moderators...again.
Was your "OMG" meant in a good way, as in Oh my God - That's an amazing idea? Or negatively, as in "Oh my God - why would anyone do that?"
Personally, I go with the OMG - That's an amazing idea! I truly hope that the OP succeeds with this project, learns something from it, and shares it with the rest of us so that others can make use of what he's learned and tried. Great to see people trying out their ideas in the real world, especially one that hurts no one and can lead to some novel approaches to operating an RV.
It’s hard enough to make a “all electric” coach that uses diesel/Aqua Hot for heat, rarely propane as the tank is to small, into a off the grid machine. Biggest obstacle is running the AC on batteries...yes it can be done if you throw enough money at it. Rarely are heated floors DC current...to many amps so they are 110V and used when on shore power, but if you have enough solar and batteries to run the ACs (OK, probably only one) you can heat the floors too. At least with AC you need it more during the day (sun is shining) unlike heat that’s needed more when the sun is not at a good angle or not even up.
Even though the OP is replacing his floors, putting 24V DC heating instead of 110V is foolish. I will not encourage the OP to throw $$$$ into this money pit idea in a rig that’s coming up on 30 years old. Spending more than what the rig is worth to make it worth half as much to someone else doesn’t make sense to me...sorry!
Know about a guy who shoehorned 3000 watts on his roof and has over 1000+ a/h's of lithium batteries. If he has some sun, he can run his air conditioners on battery only. He does have an aqua-hot for heat and hot water though. When you figure out costs of solar controllers, inverter/chargers. panels and all the other gear you will need, you will be surprised at the cost. I can run one ac for 3 or 4 hours on battery only, and did all the work myself and still have about $5000 in the electrical system, but good luck anyway.
All of the OP's goals are well within the realm of possibility, if they are dedicated to doing it.
We have a fifth wheel, that we bought new in 2015. We're approaching the same $$ amount in mods as we spent on the rig itself, and have no regrets. We don't worry about resale value, as this is a rig we intend to travel in, maintain, and repair for the foreseeable future - rather than replacing it. We do care about insured value, which required a separate appraisal at our expense to increase the insured value - something to consider when making these sorts of changes. This is our home (we sold our house and full-time) and are very happy with our decision to spend the money to make our lives in it more enjoyable. In our case, having the rig we want easily trumps resale value on our priority list. We boondock on BLM/USFS land most of the time, spending maybe a week or so in a park every two to three months if we can't find desirable free camping near where we want to stay.
We have 3kW of solar, 22.8kWh of LiFePO4 (48V, ~1800AH@12V), 30K of mini-split HVAC and a lot of other mods. We have our mini-splits - which works better than the factory rooftop ACs ever did - controlled 24/7 via thermostat and keep the rig a constant 70 during the day and 64 at night, wherever we are -- staying in places that range from freezing during the day to over 100F. We very rarely have to run the generator and prefer it that way.
The OP isn't foolish at all if they will actually use and enjoy the work they do.
That being said, lets look at some of the figures behind it. We averaged $31.87/night in park fees (weekly or monthly discounts commonly used and included in those figures) prior to the solar/HVAC installation and now average about $10/week in dump fees. That's a savings of roughly $213.09 per week. If we spend a conservative 80% (~42 weeks) of the year boondocking instead of in parks, that saves us approximately $8949.78 per year. In a few years, that exceeds the ROI on solar. It will eventually pay off, if you use it accordingly -- if that even matters to you. That doesn't even account for the fact that we are now Thousands Trails members and most of our park time is in TT parks - parks that were mostly off the table due to 30A service before. Once our TT membership ROI is reached (around 200 nights, half of which we've already used), the savings will accumulate even quicker. We opted for TT, in part, because of the lack of boondocking up the east coast and abundance of TT parks there. The numbers are a lot more nuanced than you probably realize as an armchair observer.
Here are some ideas I have been thinking about that may help you on your project.
Look at AM Solar they have a transfer switch you put after your inverter that lets you run your whole rig (both legs of ac) off of one inverter. ( I just saw a YouTube video by Jared ______(?) about it.
That will let me use a 5000va inverter, which should be good.to run everything ( just not all at the same time).
24v min battery - 48 would be better. I am thinking about making my own battery. Electric car parts. Com has just the cellls - then I was thinking about rec bms for the bms - because it can connect directly into all the Victron stuff ( mppt’s Cerbo GX, inverters, etc).
For the 12 v side, I was think of putting one marine battery lead acid battery. Then using a 48v or 24v to 12 volt converter to run all the 12 v stuff. If my 12 v draw was more than the converter could handle - it would pull down the 12v battery a little. This way I keep the emergency battery assist to start the chassis engine.
Heating I always figured was way to energy intensive other than using a little to supplement from excess solar.
Good luck with your project.
You can use a Victron Autotransformer to step up 120V output from a single inverter to true split phase 240V - a better solution than AM Solar's or a NO/NC switch. Or running two inverters isn't really an issue, and you can use an Autotransformer to load balance your 120V loads across both inverters, so you never have to worry about overloading a single inverter and can even access the capacity of both inverters on a single leg.
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