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RobD.

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I have a single 12v 100Ah LiFePo4 battery in my 5th wheel now, but want to change it out for a larger form factor such as Enduro Battery in the 2-300 Ah rating. I don't have solar currently, but may/will add it at some point. My main objective is to add an invertor so I can run my absorption fridge while traveling and run the fireplace when it's cooler outside but not cold enough for the gas furnace. I do have a 5500 kw Onan generator for A/C loads. Boondocking is also something we want to do more of.

My question is, should I consider future proofing my build by starting off with a 24v system? I plan to use the Victron Multiplus II 2x120, but haven't decided on voltage rating yet. I do understand I would need a DC/DC converter, which adds cost. But is it more than the cost savings of lighter gauge cables smaller rated MPPTs for 24v? If you suggest 24v, should I consider 24v batteries in parallel or 12v in series? I know batteries prefer to be in series. At least with Enduro battery, two 12v 200 Ah batteries are only $40 cheaper than two 24v 100 Ah batteries. Voltage, Amp hours, and Kw hours would be equal in both scenarios.

Rob
 
I would start by figuring out how much rewiring it would take to move from 12v (existing) to 24v.
Then you could evaluate if the 12v loads could run from a step down converter (24 to 12) or if the loads really need to stay 12v (think power levelers, etc.)

The advantage of the higher voltage is that you can use smaller wires and have less power loss to heat. In high amperage applications, it becomes harder and harder to "do it right" with 12v.

In my case, I had so many 12v loads that it didn't make sense for me to do anything but stay 12v. And a number of them were things like Slide Out motors, leveler motors, compressors, etc. It just didn't make sense to try and adapt all of that to higher voltage. So I just had to increase the wiring size and fuses to match and understand those limitations.
 
I would start by figuring out how much rewiring it would take to move from 12v (existing) to 24v.
Then you could evaluate if the 12v loads could run from a step down converter (24 to 12) or if the loads really need to stay 12v (think power levelers, etc.)

The advantage of the higher voltage is that you can use smaller wires and have less power loss to heat. In high amperage applications, it becomes harder and harder to "do it right" with 12v.

In my case, I had so many 12v loads that it didn't make sense for me to do anything but stay 12v. And a number of them were things like Slide Out motors, leveler motors, compressors, etc. It just didn't make sense to try and adapt all of that to higher voltage. So I just had to increase the wiring size and fuses to match and understand those limitations.
My idea was to leave everything as in in the RV and use a step down converter to power the 12v circuits. I do see what you're saying tho. I, too, have hydraulic leveling and slides as well as electric slides. So it's a mix of higher amperage loads with 12v lighting. The complexity might not be worth the potential savings. I really don't have a preference other than I don't want to have regrets later.
 
Victron is bringing its 24-volt Multiplus-II x2 to America later this year (currently Europe first). IMO I’d go with 24-volt batteries in parallel. 24-12v converters vary in features and price (research reviews). You won’t need to change your 12v wiring to 24v. The 12v out line runs to the DC panel and its loads. You can create your layout, and see what your savings are via awg pricing.
 
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Alternatively you could keep a 12 volt sealed lead acid battery as a buffer for the big 12VDC loads.
More complexity and expense though.
 
My main objective is to add an invertor so I can run my absorption fridge while traveling and run the fireplace when it's cooler outside but not cold enough for the gas furnace.
To run the absorption fridge on electric will use 350-400 watts from the battery.
The fireplace I assume is electric and will consume 1000+ watts.

Both of these ideas are better utilized when connected to utility power. Propane will last far longer than the battery for this usage.
 
I have a single 12v 100Ah LiFePo4 battery in my 5th wheel now, but want to change it out for a larger form factor such as Enduro Battery in the 2-300 Ah rating. I don't have solar currently, but may/will add it at some point. My main objective is to add an invertor so I can run my absorption fridge while traveling and run the fireplace when it's cooler outside but not cold enough for the gas furnace. I do have a 5500 kw Onan generator for A/C loads. Boondocking is also something we want to do more of.

My question is, should I consider future proofing my build by starting off with a 24v system? I plan to use the Victron Multiplus II 2x120, but haven't decided on voltage rating yet. I do understand I would need a DC/DC converter, which adds cost. But is it more than the cost savings of lighter gauge cables smaller rated MPPTs for 24v? If you suggest 24v, should I consider 24v batteries in parallel or 12v in series? I know batteries prefer to be in series. At least with Enduro battery, two 12v 200 Ah batteries are only $40 cheaper than two 24v 100 Ah batteries. Voltage, Amp hours, and Kw hours would be equal in both scenarios.

Rob
I struggled with this issue. I ended up keeping my 12 volt battery to handle surges like the landing gear but installing a much larger 24 volt pack fed by ac charger and solar to run my inverter. I have a Victron 24 volt to 12 volt dc to dc to keep the 12volt charged. I like the new setup.
 
The main advantage of 24v systems is that you can use thinner cabling because they are carrying half the current (amps). The 12v Multiplus manual calls for twin 1/0 cables protected by a 400 amp fuse(!).


Yes, you can double the amount of watts going into a MPPT charge controller (so you can have twice the amount of panels on one controller). Better efficiency and you are operating your inverter with 1/2 the amp's input.
 
To run the absorption fridge on electric will use 350-400 watts from the battery.
The fireplace I assume is electric and will consume 1000+ watts.

Both of these ideas are better utilized when connected to utility power. Propane will last far longer than the battery for this usage.
I'm wanting to use the inverter to run the fridge ILO of propane when travelling.
 
I personally don't worry about propane running the fridge while traveling.

Better option might be 12V compressor fridge. They are pretty durn effective and stable
 
Yeah, those 12v compressor cooler units are the shiznit. A little spendy, but easy to power.
Unless you're wanting to run air condition on battery power, 12v is much simpler.
I was surprised my lpg ducted furnace used 12A. I thought they were more like 8.
The lpg water heater works just killer as well.

 
I have run my absorption fridge on inverter-electric a couple times when the igniter was being temperamental just as I wanted to roll. Arrived with a low battery as expected. The charge line from the truck could not keep up. Fridge worked, food was cold. Cleaned the igniter at the destination and all was normal.

Is there trouble with the fridge during transit or is this just wanting the propane to be shut off while in motion?
 
I personally don't worry about propane running the fridge while traveling.

Better option might be 12V compressor fridge. They are pretty durn effective and stable
Me, either. The experts in the Internet say you can't run the fridge on propane while driving, but I've never had a problem. If the itty bitty little flame ever blew out, then the gas valve just shuts itself off.
 
I have run my absorption fridge on inverter-electric a couple times when the igniter was being temperamental just as I wanted to roll. Arrived with a low battery as expected. The charge line from the truck could not keep up. Fridge worked, food was cold. Cleaned the igniter at the destination and all was normal.

Is there trouble with the fridge during transit or is this just wanting the propane to be shut off while in motion?
More of a preference to not travel while using propane. I've seen too many RV fires in my travels to want to do it anymore.
 
More of a preference to not travel while using propane. I've seen too many RV fires in my travels to want to do it anymore.
Fair enough. Just saying running the fridge in transit is reasonably practical compared to running the electric fireplace in the evening using battery power.

To get back on topic I recommend 12v power for simplicity. Multiplus is great but I am not sure it is needed. Biggest feature (to me) is the ability to combine power with a smallish generator and the RV has a 5500 Onan. Stand alone 2000 watt inverter is probably all that is needed to run the MW or brew some coffee for a few minutes. Existing battery charging system is probably fine. I would prefer to spend that saved money on more battery or solar.
 
More of a preference to not travel while using propane. I've seen too many RV fires in my travels to want to do it anymore.

As an aside, I suspect this has more to do with the danger of overheating a gas-absorption refer, and less to do with 'traveling while using propane'.
Consider a ARP controller. I have their version 3.1 from about ten years ago, works great, has never had an overheat shut down. Sensors on burner and coils. A worthwhile investment.

And yes, these appliances need regular maintenance to keep the igniter and burner clean and working properly. Same for gas-fired water heater. I have experience with them going back forty years.

ARP Fridge Defend:
 
Don't fear the fridge. I run my absorption refrigerator on the road all the time. There was a recall on the Dometic absorption refrigerators. That recall was to address the potential fire issues.

However, when my absorption refrigerator dies, it will be replaced with a DC compressor model.

A 12 volt system is a lot less complicated in your case. At pointed out already, the slides and leveling system will require a hefty step down converter, or two. You can still go with the Multiplus II. I helped a friend install a (12 volt) Multiplus II in his fifth wheel last year. It was a fairly quick install that also included four 100 Ah Lion Energy LiFePO4 batteries.

I too have an on-board Onan 5500 watt generator. I rarely use it now because my PV/LiFePO4/Multiplus system takes care of 99% of my needs. That remaining 1% is when it's hotter than hell (Moab in August) and I need to run the air conditioner. My generator gets exercised monthly, following the recommendation in the Onan owner's manual.
 
Victron is bringing its 24-volt Multiplus-II x2 to America later this year (currently Europe first).
This makes no sense. European 230v is single phase. One hot. There is no reason for the 2x version of the Multiplus II over there.
 
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