12v for a trailer, but 24v is more efficient.

[jvbutter01]

I have convinced my self to get the 12v/3000w Victron multiplus. Nice all in one package. Just about ready to pull the trigger, abut I keep thinking about 24v systems are more efficient. I have not purchased solar panels yet. My system is only 2 4cell LiFePo batteries under the bed replacing my FLA batteries. I need the multi for future solar panels, also 110 output for the TT and the charging of the batteries . we have soem 12v lights in the TT, and usb outlets alos it has 12v motors on board for tongue jack, awning etc. Can i just use 24v to 12v converter for the few motors? NO i don't know the amp draw at the moment. We only use 1 motor at a time, tis all manual actuated, so I can imagine taking more than 20a draw for each individual motor. If i do, it ads another component to the system, but then i can get cheaper 24v panels on the roof and smaller diameter cables battery to charger. If it matters, i have a 33ft TT, with 30a service. Batteries in front, and the fuse panel is 2/3 towards back.

 

[stewchi]

If you have native 12v loads and the system is under 1000ah of storage and 1500W of solar then IMHO 12V is better. You can run the PV panel in series with an MPPT up to 100V so your wire size for the long run of solar back to the MPPT can be 10G. The short pieces between the batteries and inverts cut off etc are small runs and not expensive or overly difficult to run bigger wire.
Unless you already need a DC to DC for another reason then keeping it 12V it simple and you can always pick up a 12V battery or charger on the road if you have a failure. 24V makes it harder to source field repairs.

 

[chrisski]

Yes you can use a converter. If i do a 24 volt conversion, I will use a 70 amp converter to power 50 amp 12 volt jacks.

I think you need 24 volts when you use more than 2000 watts more than a couple minutes at a time. That can be 160 to 200 amps going through wires. I also think you need 24 volts to use a 3000 watt inverter because that is. 250 to 300 amps at 12 volts. Fusing and wiring get very expensive.

 

[sunshine]

Stay with 12v.
The extra cost of thicker wire is recuperated with your first 12v item purchase.
Even many larger diesel trucks have reverted to 12v rather than 24v.

 

[time2roll]

If the design is to use more than 2000 watts I would be in the 24v camp.
Or pare your needs back to 2000 max. Keep in mind 2000 watts will run anything that plugs into a regular 5-15 outlet.

 

[Supervstech]

Panel voltage is irrelevant to the conversation. As the mppt charge controller you DEFINITELY should be using doesn’t care what voltage panels you use, just size the controller output to handle the watts you need at 12V, and wire to the bank properly for the amps.
While you could use step downs for the small motors you use, sizing for the maximum load put on the inverter is the consideration you want to make on.
24V inverter uses half the amps at the same wattage. 3000W quality inverter can draw over 500A when surge loads kick in... 6000 or in some cases 9000W is a LOT of amps at 12V. Be sure EXACTLY what you plan to draw from the inverter before finalizing your decision on battery voltage.

 

[jvbutter01]

Hello @stechi
yes I do have 12v loads that is the motors i spoke of,
The lights in the TT are 12v so there is that. I would use them after sundown. There is a need for my AC on the roof. that is the biggest load.

@chrisski
yes I think i saw another post talking about a dc/dc from amazon and the 70a converter. this what sparked my idea. I didnt want to run over you post.

@sunshine,
What "first" 12v item you speak of? I'm not adding any more 12v items to the TT.

@time2roll, yes I will have AC that I will run at times, its 30a

@Supervstech
thanks for the thoughts, you seem to be pushing towards the 24v system. WE have been out many times last year, never was it hot enough for AC, when boondocking. However I would like the option. I know the AC wont last very long on batteries along. Currently i only have 8 - 280ha batteries, wired in 2 banks of 12v. Maybe running the AC is a pipe dream needing to be capped off and forgot about.

 

[Sojourner1]

If you want to run A/C you better think of a big battery bank or have enough solar to offset. Saying you have 2 4cell LiFePo batteries doesn't really say the sizeof the system.

 

[Sojourner1]

Currently i only have 8 - 280ha batteries, wired in 2 banks of 12v. Maybe running the AC is a pipe dream needing to be capped off and forgot about.

560ah can give you a short run time if properly sized wire and equipment to go with.
I have run my 15k a/c unit for 4 hours off of solar/ batteries, the SOC on the pack was 69% when stopped. The solar started contributing 75a +/- but it drops as the sun does in the afternoon, batteries contributing 55a + increasing as solar decreases. I have run the a/c off just batteries for an hour to give a quick cool down. There are other low draw items running during these times, tv, humidifier, laptops, phone booster, fans.
Bottom line though if your going to want or need a/c for long cool down periods nothing beats the generator.

The 12v 3000w inverter has been on continuously since day 1 of install over 5 years ago.

I do live off my system fulltime and at times forget that and turn the microwave on while the coffee pot is brewing, 225a +/- or nearing 2,900w. Or the other day a/c going and turned the microwave on and glanced 275a on the display before remembering and turning the microwave off.

I personally have had no issues running the 5th wheel and all components in/ or off of 12v 3000w inverter/ charger with 1,280w solar contributing during the day.

Edit: should note that a Micro-air easy start was added to the a/c unit, the locked rotor amps was a hit or miss starting issue before adding. I have seen it on my display climb briefly to 190a before settling down.

 

[stewchi]

I went a different route with my setup which all comes down to how you use it. I kept the stock 1000W inverter to run most things in the camper. I don't need the microwave when camping but do use it if I am on hookups (RV park or my backyard). If I need the AC while off grid I use a small generator running on propane with a Micro Air easy start on the AC. If I am off grid its usually somewhere I don't need the AC so its rare I needed but mainly designed it so I could cool the camper down before bed if temps are higher than I like to sleep in at bed time. The amount of available surface space on my 23ft camper is only enough for 400W (335W actual output) of solar with the AC running I am pushing about 1200-1400 watts so I would drain my batteries in 2 hours (200AH). Wasn't practical for my situation to size the DC system to power the AC, generator works fine and is a good back when the sun aint shining.
I also switched from a keurig to an aeropress, the aeropress uses no electric, I heat the water on the stove (propane). I like the aeropress so much I take with with me when I stay in hotels.

 

[jvbutter01]

@stewchi @Sojourner1 it sounds like your usage will be close to mine. Boondocking, will just be cooling off before bed if too hot. Not necessarily running all day. My system is very young right now. My biggest concern after getting my TT ( 1.5yr ago) was the low supply of FLA. So i jumped onto a group buy of the 280ah. Now I'm wanting 120v for coffee and AC if needed. Also looking into a pellet smoker. 110vs12v is the next question i have to decide. Either way. new system, Multiplus is coming, solar regeneration will be next. Need to get some measures from the roof when I get it home this weekend. then I know how much i can put upstairs. I think it will come down to the design if i need AC, I can generator it, if not run the system on battery.

 

[HRTKD]

@jvbutter01 , my opinion is that most RV travel trailers are better off staying 12v. When you get into the big fifth wheel trailers with multiple A/C units, the line between 12v and 24v becomes a lot clearer.

A 24v system adds complexity and cost. You'll need a 12v->24v converter to charge from the tow vehicle. Then you need 24v->12v converter(s) to handle the 12v loads. Any cost savings in using smaller cable due to lower amperage is eaten up by the additional converters. I would be hard pressed to find room for more components like that in my compartment.

My 560 Ah LiFePO4 battery bank should power the A/C just fine once I get the right inverter. Yes, the cable will need to be 2/0, probably 4/0. But that's only 4' of that cable, round trip. Not a big cost.

 

[HRTKD]

@stewchi @Sojourner1 it sounds like your usage will be close to mine. Boondocking, will just be cooling off before bed if too hot. Not necessarily running all day. My system is very young right now. My biggest concern after getting my TT ( 1.5yr ago) was the low supply of FLA. So i jumped onto a group buy of the 280ah. Now I'm wanting 120v for coffee and AC if needed. Also looking into a pellet smoker. 110vs12v is the next question i have to decide. Either way. new system, Multiplus is coming, solar regeneration will be next. Need to get some measures from the roof when I get it home this weekend. then I know how much i can put upstairs. I think it will come down to the design if i need AC, I can generator it, if not run the system on battery.

for now, I'm running all my 120 Vac loads off of a 1000 watt inverter, except for the microwave and A/C. For those two items, I crank up the on-board generator, which is only a couple minutes in the case of the microwave. I don't use the A/C much since I boondock at high elevations.

 

[jvbutter01]

Thanks Jim for chiming in, I remember some discussions in the past about your 12v system. Hoping you would give some input. I'm leaning the same way... generator for AC and 110 converter for the rest. I guess I dont really need the 3k watt Multi if i go this way.

 

[eXodus]

A 24v system adds complexity and cost. You'll need a 12v->24v converter to charge from the tow vehicle. Then you need 24v->12v converter(s) to handle the 12v loads. Any cost savings in using smaller cable due to lower amperage is eaten up by the additional converters. I would be hard pressed to find room for more components like that in my compartment.

no you don't
You can keep the Camper 12V system untouched.

Just run 24V Battery - Inverter (hybrid charger) 120V - Converter (already existing by factory) 12V.

You got a bit of loss in the system - but when you don't have large 12V loads - very easy system

 

[jvbutter01]

@jvbutter01 , my opinion is that most RV travel trailers are better off staying 12v. When you get into the big fifth wheel trailers with multiple A/C units, the line between 12v and 24v becomes a lot clearer.

A 24v system adds complexity and cost. You'll need a 12v->24v converter to charge from the tow vehicle. Then you need 24v->12v converter(s) to handle the 12v loads. Any cost savings in using smaller cable due to lower amperage is eaten up by the additional converters. I would be hard pressed to find room for more components like that in my compartment.

My 560 Ah LiFePO4 battery bank should power the A/C just fine once I get the right inverter. Yes, the cable will need to be 2/0, probably 4/0. But that's only 4' of that cable, round trip. Not a big cost.

Yes I currently have same 560ah battery bank. cable size is an issue, currently batteries are in front, and the inverter my thinking should go close to the power box. However this means running 4/0 wire front ( under bed) to the mid section about 20ft towards rear to power box. This would keep the multi close to the power panel, and where i plan to run the cables from solar down the closets to the box also. Not sure where to run them up front.

 

[grizzzman]

Yes I currently have same 560ah battery bank. cable size is an issue, currently batteries are in front, and the inverter my thinking should go close to the power box. However this means running 4/0 wire front ( under bed) to the mid section about 20ft towards rear to power box. This would keep the multi close to the power panel, and where i plan to run the cables from solar down the closets to the box also. Not sure where to run them up front.

You realy need to put the inverter as close as you can to the batteries 120 volt losses are MUCH easier to deal with.

 

[jvbutter01]

ok, thanks for the tip. I will just run a 110v 10/2 wire to the panel then. shouldn't be too bad.

 

[HRTKD]

no you don't
You can keep the Camper 12V system untouched.

Just run 24V Battery - Inverter (hybrid charger) 120V - Converter (already existing by factory) 12V.

You got a bit of loss in the system - but when you don't have large 12V loads - very easy system

I would not want to run the inverter just to have 12v power.

 

[eXodus]

I would not want to run the inverter just to have 12v power.

you leave the full 12V system there - including the lead battery. They keep your 12V alive when then inverter is off.