12v or 48v system in RV?

[justinm001]

For me, I'd personally prefer to stay with 12v on an RV, and just use two Victron Multiplus 3000 in parallel to get 6000w, if I needed to go over what one 12v inverter could do, because I wouldn't want to fuss with DC-DC buck converters on everything to get back down to 12v for the 12v accessories.

Or if I really wanted to go 48v (doubtful I'd ever decide that), I would just build it alongside (add in the 48v battery bank) and leave all the 12v stuff alone, and use one master 48v to 12v DC-DC charger to charge the 12v packs from the 48v pack, or something to that extent. I guess it depends on how much 12v stuff one uses on their RV..

The problem is you'd still need 500amps of 12v just 250a on each inverter. This means you likely need 3 batteries (if bms is only 200a) and they can't be wired together so all 3 need equal length cables to something like a lynx power-in then need the shunt and buss bars all to be 600amps or so to handle the 500a inverters and the 12v loads.

Running the same in 24v is 250a which allows you to just wire the batteries together and run off opposite posts all using 4/0 wire to a 300a buss bar and shunt. Which saves like a grand, then just get a $130 70a 24 to 12 Victron Orion 70a forbl the 12v loads.

 

[justinm001]

I don't have a boat (still testing the idea of boats w/ dollar bill bonfires), but I believe they sometimes have "split systems" (12v & 48v).

Depending on the actual size & carrying capacity of your "travel trailer", it might be possible to have a full 48v system (inverter, battery-bank, panels) for all heavy-draw items, and a 12v "battery-bank, charger" system for all 12v items. The 12v side could be recharged via shore power, and the 48v system could step in as shore power to the 12v system. If done right, possibly no 48v to 12v converter needed.

Purely from a design standpoint, I'd do a planning diagram of two "bubbles" of components (48v & 12v). With these laid out on paper, you might be able to spot the relationships between all the components. A bit more planning, and you might be able to transfer very efficient wiring runs between devices and the 48v or 12v systems, directly onto your travel trailer spaces.

Hope this helps ...

This is basically what I did with my coach. Pair of 48v quattro 5000s for most AC loads and to pull 50a from shore, then have a 12v quattro 5000 which grabs AC power from the 48v inverter to charge my 12v system and it also powers 1 AC and a few outlets.

I plan on using alternator power and a couple small solar panels for the 12v to keep it topped off when not on shore and when on shore it just passes power thru the 48v. Also allows me to set logic to pull from 48v to 12v through the AC which loses some efficiency but still works. Plus I get a separate input so can plug in the 12v directly too and pull a ton more power. I'm starting to play around with Node red that Victron has for their cerbogx so both systems can talk together and plan to have one tell the other what power it's on so it changes. Right now I just use the screen and change it to invert only or set the input limit low so when I run the 1 ac it uses both inverters together.

 

[MTC1014]

wow I cannot believe all the replies in less than a day. I can tell this community is going to be great for this new adventure of learning solar. Hopefully one day I'll be able to contribute more..

How many watts do you need? If more than 2,500, then 48v. Under that, 12v should simplify things.

I think I'll be able to squeeze 6x 250w panels to start, and possibly add a 400w suitcase.

Can you explain this more? Some people think a “little bit” of air conditioning is running it full blast for 5-8 hours. Also it depends upon the energy needs of your ac unit and whether or not it will work with a soft start device.

How many ac units does your rv have? If more than one, you’re going to need a huge solar system as running even one can be challenging unless you size everything right and keep your wire runs short. Ie, place your battery and inverter as close to the ac unit as you can get away with.

I just say a little bit because I realize running the A/C non stop is not going to be possible with this current setup. I have a 2023 Intech Terra, 26ft. it has 1 15k BTU. no soft start, but I may add one if that will really make a difference. it looks like on startup I've seen it pull around 1500-1700w. I really think my install space is going to be limited, so I want to get everything going first, and then see how big of a bank I can add. Down the line if I end up keeping this trailer and not upgrading, I'd likely install a more efficient mini-split.


I think this thread has convinced me to keep it simple with 12v, especially for my first install, but absolutely go with Victron components. Everything but 3 or 4 items run off 12v DC.

 

[justinm001]

Definitely get a soft start. With just 1 AC and not much other ac loads I'd stick with 12v and get something like a mp2 2x120 3000w if you have 50a shore cable or just the mp1 3000w if only 30a. That'll give you 2400w AC power which is enough then run 4/0 wire

 

[fpgt72]

Sorry for chiming in here but I am trying to learn as well. I have, from what I guess is a fairly large 12v system. My reasons for doing that are basically 12v stuff is much more available locally just about everywhere, and I am pretty firm in the "tin foil hat" camp with thinking on how the world is going.

I am using this inverter feed with 4awg wire, "real" copper is expensive, but not horrid. 4awg wire also ties the batteries to the bus bars.


With everything on this little gizmo shows me the max draw that everything will pull. I have checked this against "better" meters and it is in the ball bark .X of being accurate, like .3 ball park.



That red wire, or the black for that matter are cool to the touch, no difference in temp that my fingers could tell on a hot summer day.

So my question is, am I screwing up somewhere. This system is generally "off" when I am at work, then in my shop when I am out there it runs the lights, radio, fans and such. With a "normal" draw I have run all day on the batteries, being 6 to roughly noon, then off for lunch, then back out till roughly 4, running everything I need out there but the high current things. Welders and such.

I was wanting to run the AC off of it as well but it looks like I have hit the limit on 12v. I really don't want to change things, so I might just punt the idea all the way around, I like the way the thing works as is and am very happy with it. I have a feeling I have the "juice" to do the AC, window unit 240v. But it seems my options for a 240 inverter in 12v are limited.

Am I missing something

Sorry to hijack the thread.

 

[justinm001]

Sorry for chiming in here but I am trying to learn as well. I have, from what I guess is a fairly large 12v system. My reasons for doing that are basically 12v stuff is much more available locally just about everywhere, and I am pretty firm in the "tin foil hat" camp with thinking on how the world is going.

I am using this inverter feed with 4awg wire, "real" copper is expensive, but not horrid. 4awg wire also ties the batteries to the bus bars.
View attachment 167483

With everything on this little gizmo shows me the max draw that everything will pull. I have checked this against "better" meters and it is in the ball bark .X of being accurate, like .3 ball park.

View attachment 167484

That red wire, or the black for that matter are cool to the touch, no difference in temp that my fingers could tell on a hot summer day.

So my question is, am I screwing up somewhere. This system is generally "off" when I am at work, then in my shop when I am out there it runs the lights, radio, fans and such. With a "normal" draw I have run all day on the batteries, being 6 to roughly noon, then off for lunch, then back out till roughly 4, running everything I need out there but the high current things. Welders and such.

I was wanting to run the AC off of it as well but it looks like I have hit the limit on 12v. I really don't want to change things, so I might just punt the idea all the way around, I like the way the thing works as is and am very happy with it. I have a feeling I have the "juice" to do the AC, window unit 240v. But it seems my options for a 240 inverter in 12v are limited.

Am I missing something

Sorry to hijack the thread.

4ga is completely different than 4/0 gauge. 4ga is 60a vs 260a for 4/0. You're running a 3000w inverter but wiring can only handle 800w or so. But since it's always cool I'm assuming you don't have a high load which is fine. But yes copper is very expensive so if you got a 48v inverter you'd be able to use 1/4 the wire size.

 

[Johneb]

I don't have a boat (still testing the idea of boats w/ dollar bill bonfires), but I believe they sometimes have "split systems" (12v & 48v).

Depending on the actual size & carrying capacity of your "travel trailer", it might be possible to have a full 48v system (inverter, battery-bank, panels) for all heavy-draw items, and a 12v "battery-bank, charger" system for all 12v items. The 12v side could be recharged via shore power, and the 48v system could step in as shore power to the 12v system. If done right, possibly no 48v to 12v converter needed.

Purely from a design standpoint, I'd do a planning diagram of two "bubbles" of components (48v & 12v). With these laid out on paper, you might be able to spot the relationships between all the components. A bit more planning, and you might be able to transfer very efficient wiring runs between devices and the 48v or 12v systems, directly onto your travel trailer spaces.

Hope this helps ...

This is what I did. Added a Samlex EVO4248 AIO with a 302ah 48v DIY battery. Left the 12v system alone. Still working on solar. I should add I have a 35 foot fifth wheel with a huge basement area.

 

[Tomthumb62]

wow I cannot believe all the replies in less than a day. I can tell this community is going to be great for this new adventure of learning solar. Hopefully one day I'll be able to contribute more..


I think I'll be able to squeeze 6x 250w panels to start, and possibly add a 400w suitcase.


I just say a little bit because I realize running the A/C non stop is not going to be possible with this current setup. I have a 2023 Intech Terra, 26ft. it has 1 15k BTU. no soft start, but I may add one if that will really make a difference. it looks like on startup I've seen it pull around 1500-1700w. I really think my install space is going to be limited, so I want to get everything going first, and then see how big of a bank I can add. Down the line if I end up keeping this trailer and not upgrading, I'd likely install a more efficient mini-split.


I think this thread has convinced me to keep it simple with 12v, especially for my first install, but absolutely go with Victron components. Everything but 3 or 4 items run off 12v DC.

If you need a lot of 4/0 wire, then shop around for the best price for a whole roll. Not sure how long but I guess maybe 100’.

If you need less than that, I highly recommend batterycablesusa.com. They have all high quality wire and good prices and ship fast.

 

[Samsonite801]

The problem is you'd still need 500amps of 12v just 250a on each inverter. This means you likely need 3 batteries (if bms is only 200a) and they can't be wired together so all 3 need equal length cables to something like a lynx power-in then need the shunt and buss bars all to be 600amps or so to handle the 500a inverters and the 12v loads.

Running the same in 24v is 250a which allows you to just wire the batteries together and run off opposite posts all using 4/0 wire to a 300a buss bar and shunt. Which saves like a grand, then just get a $130 70a 24 to 12 Victron Orion 70a forbl the 12v loads.

Yeah, like I said, that's just what I might've considered (if I had initially needed more than 2800-3000w on my 12v system).. I have six 280Ah 12v batteries so that's around 1680Ah, so in this case, sure, just add some more cables onto the bus bar. Maybe consider a 1000a Victron shunt instead of the 500a shunt I had purchased. The current system doesn't draw more than 250a though..

On my current 2800w Magnum inverter setup (I have that only because the RV came with it), I ran two 2/0 runs back from the battery, in parallel (in a PVC conduit), which for me was way easier to manage it could fit two more cables if I had wanted (two 2/0 cables bends easier than a single 4/0 cable run). I can run one of the two roof AC units all day (at a time) with the 2800w though (both have soft starters on them).

I'm actually using my 12v (only with that Magnum 2800w inverter), parked in the shop now, and working on building up my permanent 48v system which will serve for the long run. So I am kind of doing what I had said before in my previous post about building out a 48v system alongside the 12v one. It's not actually in the motorhome, but on a wall basically right next to the motorhome.

Once the other 48v system is going, I will likely just hook the 50a motorhome cord up to run the Magnum charger off the system with the 48v, but leave 12v system's solar connected as it was already, and supplemental charging can come from the 48v system if needed.

I don't know, there's like 50 ways one could do this.. Different people may have different needs and want to do theirs in some other way, depending on what they want. Mine was more like to build a decently robust temporary 12v to start with, later build 48v system for shop/property. Build house, move loads off of the 12v system, but it is still there in place and operational in case I want to travel with the motorhome later, or if I just need some backup means of power.

Mine's not the best setup in the world, but sometimes you have to work with the parts and budget you already have.

 

[Tomthumb62]

don't know, there's like 50 ways one could do this.. Different people may have different needs and want to do theirs in some other way, depending on what they want.

This is essential to keep in mind when reading this entire forum. Some people get fixated on doing it a certain way, when it’s just the best way to do it in their situation. Many times I’ve had to explain my use case and then they’d back off and say, oh yeah that makes more sense to do it that way.

That said, once you learn the different personalities here and know how to translate some of the super smarter folks info into your use case, you can learn a lot!

 

[fpgt72]

4ga is completely different than 4/0 gauge. 4ga is 60a vs 260a for 4/0. You're running a 3000w inverter but wiring can only handle 800w or so. But since it's always cool I'm assuming you don't have a high load which is fine. But yes copper is very expensive so if you got a 48v inverter you'd be able to use 1/4 the wire size.

Not sure I understand, I have had several amp meters show me 100+a, and with it being 12v at its best it is only a few volts above that.

The same circuits also show when on "main" have the same amp draw when on the inverter. I know I am missing something, forgive me I am new.

I have done "house electrical" for decades, so I got a good grip on that. I am new at this "solar stuff". But it would seem the current coming out of the inverter matching what the current is when on "mains" or "grid" I am working apples and apples. I understand the DC going into the inverter itself is oranges.

There is a 300A service running into the shop, with a 100a sub panel in the barn close by, not much on the barn just a couple battery tenders for tractors mowers and such.

I have hit "overload" on the inverter before. Once with my big belt sander when everything else is on, and again with the boost battery charger. I am not sure now if the cable could not deliver the current or the inverter said, no way I am out. I think it is the latter as the inverter does shut down. That was to me, a note to self moment, don't turn this stuff on when running in battery.

Sorry I am a bit confused.

 

[justinm001]

Not sure I understand, I have had several amp meters show me 100+a, and with it being 12v at its best it is only a few volts above that.

The same circuits also show when on "main" have the same amp draw when on the inverter. I know I am missing something, forgive me I am new.

I have done "house electrical" for decades, so I got a good grip on that. I am new at this "solar stuff". But it would seem the current coming out of the inverter matching what the current is when on "mains" or "grid" I am working apples and apples. I understand the DC going into the inverter itself is oranges.

There is a 300A service running into the shop, with a 100a sub panel in the barn close by, not much on the barn just a couple battery tenders for tractors mowers and such.

I have hit "overload" on the inverter before. Once with my big belt sander when everything else is on, and again with the boost battery charger. I am not sure now if the cable could not deliver the current or the inverter said, no way I am out. I think it is the latter as the inverter does shut down. That was to me, a note to self moment, don't turn this stuff on when running in battery.

Sorry I am a bit confused.

If the wires from the battery to the inverter are 4 gauge you can only run 70 or 85 amps through it so 1105w (13volts x 85amps) when using the battery. If not on battery and its just passing thru the 120v power then you can run as much as its rated for.

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.

www.cerrowire.com

 

[Samsonite801]

Not sure I understand, I have had several amp meters show me 100+a, and with it being 12v at its best it is only a few volts above that.

The same circuits also show when on "main" have the same amp draw when on the inverter. I know I am missing something, forgive me I am new.

I have done "house electrical" for decades, so I got a good grip on that. I am new at this "solar stuff". But it would seem the current coming out of the inverter matching what the current is when on "mains" or "grid" I am working apples and apples. I understand the DC going into the inverter itself is oranges.

There is a 300A service running into the shop, with a 100a sub panel in the barn close by, not much on the barn just a couple battery tenders for tractors mowers and such.

I have hit "overload" on the inverter before. Once with my big belt sander when everything else is on, and again with the boost battery charger. I am not sure now if the cable could not deliver the current or the inverter said, no way I am out. I think it is the latter as the inverter does shut down. That was to me, a note to self moment, don't turn this stuff on when running in battery.

Sorry I am a bit confused.

On my RV, when I bought it, it only had certain select A/C circuits wired through the inverter, so I wound up rewiring the RV breaker panel so all A/C circuits go through the inverter (since I have no normal grid input).. Then I could run the air conditioners on inverter too, and all the outlets in the coach are going through inverter as well.. So I bridged the 2 halves of the breaker panel, and ran them all through the inverter, and wired my main ATS to only feed the inverter input in case I want to charge batteries through the grid line power cord or the Onan genset line (via ATS)...

You can check and see how yours is configured from factory.

 

[Samsonite801]

On my RV, when I bought it, it only had certain select A/C circuits wired through the inverter, so I wound up rewiring the RV breaker panel so all A/C circuits go through the inverter (since I have no normal grid input).. Then I could run the air conditioners on inverter too, and all the outlets in the coach are going through inverter as well.. So I bridged the 2 halves of the breaker panel, and ran them all through the inverter, and wired my main ATS to only feed the inverter input in case I want to charge batteries through the grid line power cord or the Onan genset line (via ATS)...

You can check and see how yours is configured from factory.

Yeah BTW, if I am running on my Onan or grid cord which is powering only my inverter input, while in charging / passthrough mode, it then CAN run both air conditioner units, where when on inverting mode / battery, it can only run one AC unit or it will trip inverter.

 

[ericfx1984]

So I've been living on a 12 volt system in an RV for the last 2 years

Knowing what I know now, struggling to and succeeding at keeping things running and making it all work together, you could not pay me to do a 12 volt system again... I do have a mini split air conditioner and a 5,000 BTU window air conditioner running, we stay cool... But there are a lot of losses in the summer when the heat picks up

There's just no way that you could talk me into doing a 12 volt system ever again It just doesn't make any sense

 

[Samsonite801]

So I've been living on a 12 volt system in an RV for the last 2 years

Knowing what I know now, struggling to and succeeding at keeping things running and making it all work together, you could not pay me to do a 12 volt system again... I do have a mini split air conditioner and a 5,000 BTU window air conditioner running, we stay cool... But there are a lot of losses in the summer when the heat picks up

There's just no way that you could talk me into doing a 12 volt system ever again It just doesn't make any sense

Yeah the general rule of thumb always had been, if you needed more than about 2800-3000w, then bump to 48v is what you'd normally opt for naturally.

While I never needed to or do it yet (go past 3000w), when I had noticed the Victron 12v Multiplus's can be paralleled it raised an eyebrow, as curious thing to try.

There is nothing wrong with going 48v (I'm sure better for many scenarios), I personally wanted to push back on moving away from 12v for the simple fact, that I run a lot of 12v appliances too, and so each of those loads would require down-conversion solutions, adding more electronics and converters that can fail too. Not a horrible switch to make for a few appliances/circuits, but again, it just depends on the person's needs, and the way they'd like to do it.

 

[justinm001]

Yeah the general rule of thumb always had been, if you needed more than about 2800-3000w, then bump to 48v is what you'd normally opt for naturally.

While I never needed to or do it yet (go past 3000w), when I had noticed the Victron 12v Multiplus's can be paralleled it raised an eyebrow, as curious thing to try.

There is nothing wrong with going 48v (I'm sure better for many scenarios), I personally wanted to push back on moving away from 12v for the simple fact, that I run a lot of 12v appliances too, and so each of those loads would require down-conversion solutions, adding more electronics and converters that can fail too. Not a horrible switch to make for a few appliances/circuits, but again, it just depends on the person's needs, and the way they'd like to do it.

I wouldn't want to run parallel inverters if possible, much rather get a Victron 5000w inverter which which I know they make the Quattro 12v 5000 and they make some MP's in 5000 but I don't think12V. I'd also split phase instead of parallel so you could charge off 50a shore but when combining multiple inverters with Victron you have to use different apps and things get complicated.

Also if going 48v you wouldn't need down converters for each load just 1 or 2 converters in parallel then another buss bar for all your 12V loads. You then get redundant converters on top of a solid stable voltage for all your 12v needs. Its better than 12V because adds a bit more protections for overcurrent/undercurrent as the converter will fry and not the electronics.... Read my post about my alternator on here, had a voltage spike and it fried a ton of electronics but with converter it fried the converter. Would have saved me thousands.

 

[fpgt72]

If the wires from the battery to the inverter are 4 gauge you can only run 70 or 85 amps through it so 1105w (13volts x 85amps) when using the battery. If not on battery and its just passing thru the 120v power then you can run as much as its rated for.

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.

www.cerrowire.com

So three different meters are telling me lies?

 

[fpgt72]

So I've been living on a 12 volt system in an RV for the last 2 years

Knowing what I know now, struggling to and succeeding at keeping things running and making it all work together, you could not pay me to do a 12 volt system again... I do have a mini split air conditioner and a 5,000 BTU window air conditioner running, we stay cool... But there are a lot of losses in the summer when the heat picks up

There's just no way that you could talk me into doing a 12 volt system ever again It just doesn't make any sense

In building my system I had a few things in mind, one of the top things is the world falling apart.

I chose 12 because it is far more common, and far more easy to power should things get "really bad".

 

[fpgt72]

On my RV, when I bought it, it only had certain select A/C circuits wired through the inverter, so I wound up rewiring the RV breaker panel so all A/C circuits go through the inverter (since I have no normal grid input).. Then I could run the air conditioners on inverter too, and all the outlets in the coach are going through inverter as well.. So I bridged the 2 halves of the breaker panel, and ran them all through the inverter, and wired my main ATS to only feed the inverter input in case I want to charge batteries through the grid line power cord or the Onan genset line (via ATS)...

You can check and see how yours is configured from factory.

This thought has crossed my mind and I am really leaning this way. I am also thinking about different things as well as playing with this stuff is just fun.