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Clean sheet design: inverters, batteries, etc.
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My only concerns are any expectation of running A/C units powered through inverters. First unless an entire bay is filled with batteries the available run time is measured in hours. They draw down batteries quickly.
But Inverter Services during our seminars urges owners to avoid the use of inverters to power loads like A/C units because newer inverters do not hold up well under the loads imposed.
Since it sounds as though you are committed to update your house electrical system your coach can do nicely as a result of its relative simplicity dry camping with a decent set of batteries. It will do amazingly well with LiFePo4 batteries. But it all comes down to economics. If you do the math it will tell you if the cost of Li is justified compared to conventional batteries and the generator run time and expense.
Under all typical loads that make sense for a generator, including A/Cs, water heater, battery charging, etc you can plan on 1/2 gallon per hour or less fuel burn. That’s a pretty cheap cost to be able to live large and not worry about managing or conserving power.
I am an advocate of Li power because my batteries not only saved me about 400 to 500 pounds, but I get far more usable hours from them compared to their equivalent AGM which means if you do go that route you can run your generator less. The only problem is by my calculations the economic payback only began after 10 years of use, making them a poor investment.
Your plan sounds very reasonable and if I were to do what you are doing I would run the generator any time I wanted to carry heavier electric loads and I would run every A/C and keep the entire coach comfortable.
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Just an update on the planning for this project. I’m going to start with a ductless mini-split that I have sitting in my shop. It’s only a 120v 12,000 BTU heat pump, but I found a way to integrate it into my interior by putting it above the pull-out sofa. I have to block the upper portion of a window to mount it, but I’m going to do the same thing on the opposite side in order to mount a TV. I think it’ll balance out okay as a design. My bedroom Cruisair still works great, and I’ve decided the other Cruisairs will not be going back in.
I’m going to do this in increments with the goal of switching to LiFePO4 batteries and good inverter/chargers, but I can take the first few steps without committing to later investments. The lingering question is what to do eventually with my 50DN alternator. Since I removed the OTR heat and air, the demands on the 50DN are just battery charging and very minimal chassis loads. If I switch to LiFePO4 for the house, I’m not clear on whether the 50DN can continue to charge both the house lithium and the remaining lead acid chassis batteries. I guess the voltage requirements are different. Having a 50DN just to top off my engine start batteries seems like overkill. Not a problem to solve now, but it’s bugging me as I try to picture my eventual changes.
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Coaches without OTR, often use the 50DN as a means of charging house batteries when A/C units are run through inverters. At 12 volts the typical A/C will draw about 130 amps, and at 24 volts it will draw 65 amps. That justifies the 50DN.
It really doesn’t mater how the A/Cs are powered, via batteries charged by the 50DN or generator because the amount of work done is the same and either way fuel is consumed for that purpose.
If I were in Chad’s position I would step back and take a long look at my options, including making use of the OTR ducting and possible whole house heat pumps, multiple high watt capacity inverters, the number of batteries, and total coach current draw, especially recognizing 50 amp RV park service is usually limited compared to most generator output which requires careful load planning, balance and management.
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Jon said:
Coaches without OTR, often use the 50DN as a means of charging house batteries when A/C units are run through inverters. At 12 volts the typical A/C will draw about 130 amps, and at 24 volts it will draw 65 amps. That justifies the 50DN.
This is exactly what I had in mind with my original post. I may have confused things when I said I wanted the 50DN to “feed the inverters.” With one or more mini-splits, I think the 50DN has enough output to keep the coach cool on all but the hottest days. I’d like to learn more about any coaches that are running AC units through inverters.
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Keep the updates coming, Chad. I use Mitsubishi mini-splits in my sun room, and master bedroom which is 25′ x 22′. Efficient heating and cooling in both locations. It will be interesting to see how it holds up on the road.
Pictures along th way would be great so that the PC can keep you motivated along the way.
Ron
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Chad, with the exception of Liberty who has gone the A/C through inverter route on later model coaches, almost all coaches are set up to run A/Cs through inverters. The inverter people do not recommend that, but most owners are reluctant to run the generators while driving down the road so they load their 50DN or multiple Bosch alternators.
Keep in mind when you load alternators like that you are generating heat in both the alternators and inverters so if you do not want to run the generator for A/C make sure you are providing cooling to the devices doing the work.
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I think I may be getting too hung up on the voltage from the 50DN. Jon, I saw a post from you over on the BGM site about your current setup, and I think you said yours was putting out 27.7 volts. Obviously not the correct voltage for charging your lithium batteries, but also doing no harm. If I place high demands on my batteries through inverter loads, the 50DN would serve to “refill” the batteries even though the voltage isn’t high enough to achieve 100% charge. If my understanding of that is correct, I then just have to ensure that the output from the 50DN doesn’t get so high as to damage it or the batteries. Apart from a circuit breaker, I’m not yet clear on how to achieve a working limit on the alternator output.
This discussion is definitely helping me, so I hope I’m not boring anyone. I really appreciate all of your input.
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If you have 24 volt invertors, do not use 2 12 volt batteries in series to get 24 volts, unless you use a bms that will manage all the batteries. Use 24 volt batteries.
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Not sure if my suggestions will help or not, but eventually I also plan on replacing the entire charging/inverter system, and I do not have bus air, and I want to cool the entire coach from inverters if possible. I am also considering a modern, high quality residential 240v mini-split with 3 zones, 2 non-ducted (front and back) and 1 ducted (middle) to replace the 2 cruiseairs and 1 rvac. I have a 2001 Featherlite H3-45.
I am in no hurry to do this, as I have a functional system, and I only would consider this if I had a large “thing” to replace, most likely the first of the “large” things would be house batteries. At that point I would consider the electrical system only, and not the HVAC just yet.
So, this is what I would consider:
2 x Victron Quattro 24v/8000VA inverters, 230/240v 50/60Hz single phase, set to 240v/60Hz. These can be daisy-chained to provide as much power as you want provided you want to buy more of them 🙂 and have 2 AC inputs with auto-switching, and the inverters can “boost” the A/C output at any point when on the A/C input that is not capable enough to power your load (so if you are on 15,30,50Amp shore power, in theory you can still run up to 2x8000KVA). One caveat with the 240V based inverter: any 120v shore power (15/30A) would likely need to be converted to 240v with a transformer.
1 x Victron auto-transformer to supply 240v split phase and 120v+N + N+120v. You can possibly choose to not use this and instead use 2 x Victron 120v inverters (they can be combined in pairs to create 240v split phase), but there is almost no cost difference (the lower cost 240v inverters make up for the transformer cost), and if 1 of those 120v inverters dies, you no longer have 240v split phase.
10-20KWH of 24v LiFePOLiFePo batteries, most likely DIY-assembled. You should get 10-20 years of life on this!
A high quality battery management system like Batrium (that can communicate with Victron and the regulator below)
A WS500 alternator regular for the DN50 designed to work with LiFePO battery systems.
A rebuild or replacement of the 50DN with 450 Amp capability (50DN+) instead of 230, so ~10KW can be provided when driving.
Multiple Victron 70-amp 24v->12v power supplies in parallel to power 12v house electric. There will be no battery balancing for house batteries.
Eventually: 4-5Kw solar PV on the roof. I have no roof airs and nearly no current roof real-estate taken at all, so lots of room for PV.
Don’t consider this a proven recipe at all. This is all just brainstorming at this point.
I am a relatively new owner, so A lot of this is subject to change. I have a lot of other stuff I want to address before I get to this stuff, and I want to be certain I intend to keep this coach for a very long time before I make such a big investment.
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Wow! That’s a great response, Andrew. Here are a few things that stood out to me:
I had overlooked the ability to configure the 230v Victron stuff to 120v/240v split-phase. Their product line makes more sense to me now.
I didn’t know you could squeeze that kind of performance out of a 50DN. I wonder if doing that and then pulling 250 amps max would make it more or less likely to fail than pulling 250 amps from its current 270 amp configuration. Being gear-driven, it is oil-cooled but very tough to access. I had planned on limiting it to maybe about 150 amps to try to avoid failure.
I plan to merge my two 12v house systems into one, and the existing battery balancing solenoid provides a perfect spot to do that. I already have two of the Victron 70 amp converters to bring the alternator output down to 12v, so I agree with that approach.
I’m keeping solar in the back of my mind, but it would have to be installed without disrupting the looks of the bus. It sounds like flexible panels aren’t ready for mainstream use yet. Am I correct that your proposed setup would allow for shore, solar, and generator use?
I appreciate your reply.
Chad
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Hello, Chad. Yes, my intention was to use shore, generator, solar, and alternator to provide power and/or charging. The solar could be used in combination with any of the other sources of power.
As for the alternator, I guess we have different placements between our coaches (mine is easily accessible). IMO, as long as the alternator is cooled adequately, I would think it would be able to operate at its max amperage. Perhaps one thing to consider would be an alternator temp sensor included in the regulator’s control. I think Victron had a video about this, where they monitored alternator temps. I believe they had a whole series of videos on charging LiFePO with alternators and how it is very different from charging lead-acid. The biggest take-away I got was that a more advanced regulator is certainly needed.
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Consider using Victron batteries and all Victron pieces. Their system is set up to handle everything. Their batteries BMS communicates with the other pieces etc, etc, etc.
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Hi Andrew,
saving your alternator is but one of the benefits of splitting your house bank into two banks, one Li and leaving at least some of your lead acid house batteries in place for the other. Using a BtoB charger will limit the amp draw the Li batteries can take from your alternator. If you want faster charging than you can get from one BtoB charger, just add a second in parallel.
Jerry
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Mikee, I plan on using mostly Victron products but they’re pretty proud of their batteries. My current plan is to go with the rack-mount batteries that are becoming popular. Roughly 1/3 the cost per Watt Hour. Here’s a video talking about them.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
Hello, Chad. Have you looked at Dakota batteries?
Ron
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