12v or 48v system in RV?

[justinm001]

So three different meters are telling me lies?

If you're running more amps through the cable than it's rated you're risking things melting and catching fire. Also your fuse should blow, provided you have one.

Skipping safety doesn't mean the meters are lying it means you're playing with fire, quite literally

 

[Tomthumb62]

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.

I have a homemade camp trailer so it came with no electrical system other than the trailer traffic lights. When I redid the electrical recently, I added an AC manual switch. Position 1 is inverter power, position 0 is OFF and position 2 is shore power. My 1000W Victron inverter can power anything (for a few minutes at least) I might want to use (power tool, vacuum, etc) but is there mostly to power the 120v mid size fridge. The switch controls all two outlets in the camper, including the one the fridge is connected to. My AC 30A charger is hardwired to the shore power input line (entire wiring for 120v is 12awg for up to 20A) so that when the switch is on position 1 inverter power, the battery isn’t trying to charge itself. The charger only works when the trailer is plugged into shore power.

 

[MTC1014]

is there a way to tell the voltage required for the MPPT to start operating? asking about on 48v. I believe in one of Will's videos, he states it requires 100 or 120v for the batteries to start charging. would this be the same requirement on a victron charge controller?

 

[justinm001]

is there a way to tell the voltage required for the MPPT to start operating? asking about on 48v. I believe in one of Will's videos, he states it requires 100 or 120v for the batteries to start charging. would this be the same requirement on a victron charge controller?

It needs to be at least 5v above the charging voltage for the mppt to turn on so 62ish volts. You really want 100v+ though so if it's not optimal conditions the voltage is high enough to pull the amps.

 

[fpgt72]

If you're running more amps through the cable than it's rated you're risking things melting and catching fire. Also your fuse should blow, provided you have one.

Skipping safety doesn't mean the meters are lying it means you're playing with fire, quite literally

There is a fuse, the cable is not hot.

 

[fpgt72]

I have a homemade camp trailer so it came with no electrical system other than the trailer traffic lights. When I redid the electrical recently, I added an AC manual switch. Position 1 is inverter power, position 0 is OFF and position 2 is shore power. My 1000W Victron inverter can power anything (for a few minutes at least) I might want to use (power tool, vacuum, etc) but is there mostly to power the 120v mid size fridge. The switch controls all two outlets in the camper, including the one the fridge is connected to. My AC 30A charger is hardwired to the shore power input line (entire wiring for 120v is 12awg for up to 20A) so that when the switch is on position 1 inverter power, the battery isn’t trying to charge itself. The charger only works when the trailer is plugged into shore power.

This sounds a little like how I did my shop, but with a few more switches. This is the best photo I have of mine.


It is a generator manual transfer panel, the plug at the bottom goes to the inverter not a generator in my case. For me Line is "short" of "the grid" middle is off, and top "gen" is running off the inverter. This in my case runs 5 different circuits, I have nothing on "F" at the moment. This way I can control in my shop what I want to run on what, well most of it. In the photo below you can see the tape on the breaker, this is what is on the transfer panel, so I know what goes where. You can see there are circuits on "both sides" of the panel. This is the "right way" to do something like this, where as using "suicide cables" are the "wrong way". This works fairly well as I have outlined in other areas with the execption of those high current devices.

 

[Samsonite801]

If you're running more amps through the cable than it's rated you're risking things melting and catching fire. Also your fuse should blow, provided you have one.

Skipping safety doesn't mean the meters are lying it means you're playing with fire, quite literally

I always like to find my favorite NEC ampacity chart and refer to it when selecting fuse / breaker sizes (of course the 80% rule applies and whatnot)...

https://media.distributordatasolutions.com/ThomasAndBetts/v2/part2/files/File_7437_emAlbumalbumsOcal20(USA)oc_1_g_nec31016pdfClickHerea.pdf

The any decent cable brand will have the temperature rating stamped on the cable for further reference and collaboration.

 

[Samsonite801]

is there a way to tell the voltage required for the MPPT to start operating? asking about on 48v. I believe in one of Will's videos, he states it requires 100 or 120v for the batteries to start charging. would this be the same requirement on a victron charge controller?

Sometimes manufacturers publish the MPPT normal operating range, and minimum startup voltage on their specs sheets for the controllers, refer to that first and see if you're so lucky to find it there.

 

[MTC1014]

Sometimes manufacturers publish the MPPT normal operating range, and minimum startup voltage on their specs sheets for the controllers, refer to that first and see if you're so lucky to find it there.

Thank you! from what I can tell, the victron mppt will turn on once the voltage is 5 above the battery voltage, so around 53 on a 48v system. the EG4 all in one doesn't turn on until 120v? makes me wonder why I would go that route other than the significant lower price.

 

[Samsonite801]

Thank you! from what I can tell, the victron mppt will turn on once the voltage is 5 above the battery voltage, so around 53 on a 48v system. the EG4 all in one doesn't turn on until 120v? makes me wonder why I would go that route other than the significant lower price.

Which EG4 model are you referring to? The 6400EX says range is like 90-450v, assuming startup maybe be somewhere around lower end obviously.

There are other factors too, like simply matching your panels and panel wiring layout (series/parallel/mix) to work well with the MPPT range. Once the Sun rises, it doesn't take long for voltage to rise up and wake up the charger, amps will take a bit longer build up to full strength.

I wouldn't worry too much about the startup voltage being low enough, just focus on matching your Voc well with the MPPT controller to begin with. MPPT controller and solar panel layout and matching go hand in hand, like a horse and carriage (and don't go over max PV volt input spec hehe)...

 

[MTC1014]

@Samsonite801 - I was looking at the 3000EHV-48 ($674)
either that, or using Victron components to piece together a system.

I'd likely be using 6x 250w New Powa panels (1500 w total).
I used the calculator on explorist.life's site, and it's showing array voltage would be around 205v, with output amperage at 26a if I wired all 6 in series. The calculator recommends the Victron 250/60

 

[justinm001]

There is a fuse, the cable is not hot.

How many amps is your fuse for? So your inverter is pulling over 100amps from the batteries using 4gauge wire and well above the charts but somehow it's OK?

 

[50ShadesOfDirt]

The beauty of parallel systems (48v and 12v), is that the 12v system isn't pulling/supporting any huge loads, so it's componentry is small and dedicated to all the 12v loads that others have listed in this thread.

Many 12v loads in any typical RV setup, and having a parallel 12v system (with or without a 12v inverter) would support all that ... it's doing what 12v does best. Power cables are much smaller, because of small loads ...

The 48v system is doing what it does best, which is supporting huge loads ... keep everything logically together on the 48v side, or even physically together, if RV layout supports or accommodates it. Now your expensive cables are "short", running between battery-bank & inverter, and only the load cables have to go where the big loads are.

The 12v busbar, or bluesea systems' 12v distribution box, are great ideas to run directly off of a 12v battery-bank ...

Finally, you get some redundancy built in, as (unfortunately) the current crop of AIO's might tend to fail on you, and either the vendor or seller could leave you hanging for quite some time in getting repaired/replaced. Being able to run off of 12v, means not everything is dead if the 48v side craps out ...

It's personal choice, of course, but parallel and redundancy don't really prove their worth until you need them (at which point it's too late if you don't have them), so you've got to plan this stuff in ...

 

[RvNaut]

These typically consume 40-50W continuously even if you don't use any loads.

Given my system is on and powering other items 24/7/365, it is a non-issue.

Additionally the first 200-300W of PV are unusable for loads as they're just feeding the inverter's idle consumption.

??? this does not compute.

Hence, there's a hidden cost to the cheap AiO - you have to buy more battery and more PV

I do not think so... You are missing a few points ... I live in my RV.. it is always on. I also built a massive battery on purpose, to handle heavier loads down the road. The AIO so many despise replaces $3500 in Victron... I live on SSI, so it was cheap or not at all... so I reject your claims as unrealistic for my situation.

One thing to mention is there isn't much 12v to 48v stuff yet

I found Victron's 48v-12v to be adequate, but will have to double up on mine as it isn't to fond of running the jacks. I do have a deep cycle 12v batt in line to act as a buffer.

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,

When I looked at my long term usage, I knew I would be asking for too much power for a 12v system... not that you can't do it with 12v, but it wastes a lot... the other side of that is that you can only pump so much into a 12v battery system at one time. I am starting with 1400 watts of solar but intend to up that to at least 3k or higher in 2-4 years. In order to efficiently absorb this much solar requires a massive 12v system and all that ought wiring. I could easily be running with a 24v system at this time and it would suffice for current needs. When I install the MiniSplit down the road, my consumption will go up. ... but again, I am fulltime, so my usage is different than most I guess.

Running the same in 24v is 250a which allows you to

or at 48v is 125a and even less issues with wiring......

to keep it topped off when not on shore

to clarify my setup, I am never on shore, and use a gen when I have to...

so each of those loads would require down-conversion solutions,

I just tapped in the new 12v feed (set to 12.9v on the Victron converter) direct from the 48v battery I built, into the existing 12v battery bay and connected to a 12 deep cycle battery to act as a load buffer. Poof.. no need to do anything else because you didn't change anythign in the 12v system other than disconnecting the existing inverter/controller from the 12 system.

 

[justinm001]

Eggo is saying the inverter will use 50w additional constantly so when calculating your solar there's a few hundred watts that are eaten up. If your solar produces 3kw per day then you have 2.5kw max usable because the extra is feeding the inverters consumption. Probably closer to 2kw.

 

[SendIt]

When I did my trailer, the power distribution was sort of far away from the battery bank. I opted to go with 24 volt so that the main run from the battery bank to the 12v distribution would be smaller gauge. You can get a 24v > 12v converter for pretty cheap. Depending on the loads and length of your wire run, using a higher voltage can save a non-negligible amount of weight and cost.

(I would have gone with 48V, but it ended up being cheaper per watt-hour to buy 8 x 280ah cells than 16 x 100ah cells)

 

[wopachop]

This thread helped a lot i still cant decide whether to go 12, 24 or 48. Trying to talk myself into saying 12v is fine.
If the RV has a large build in generator, do most stick with 12v since they need a 12v starting battery?
Also pretend the batteries can be 3 feet from the inverter and distribution panel, would 24v be silly?

 

[Johneb]

My battery/inverter are in the front of the basement of our 5th wheel. It takes 2 4 foot sections of 6/0 wire to wire up to the 240v system. I went 48v because of efficiency and less cost for wiring. Goid luck.

 

[HarryN]

It is tough to beat a 24 volt system for mobile and DIY.

It is easy to find 24 volt DC rated components and many appliance are dual 12 / 24 volt DC.

There is a large increase in inverter efficiency going from 12 - 24 volt, but going further to 48 volt the gain is much smaller.

The marine industry is full of 24 volt and dual 12 / 24 volt items that are easy to use in a trailer.

I like 48 volt setups but I would not suggest it to a beginner or frankly to the typical DIYer with DIY level tools and skills. This is especially true for mobile.

Mobile and stationary are not the same. The inside of a trailer gets bounced around a lot.

 

[sunshine_eggo]

There is a large increase in inverter efficiency going from 12 - 24 volt, but going further to 48 volt the gain is much smaller.

Please clarify what you mean by this. Example:



I see 1% gains going from 12 to 24 and another 1% going from 24V to 48V. A 1% gain from 93 to 94% is a 1.07% relative improvement, and a 1% gain from 94 to 95% is a 1.06% relative improvement. Smaller, yes, but it seems contrary to your claim. Sure, this is Victron specific, but I would expect similar ratios from other manufacturers.

If you're referring to the DC side, there's no difference. Going from 12V to 24V for a given power/cabling means a doubling of the voltage and a halving of the current, resulting in 1/4th the losses from wiring. But this is also exactly true for a jump from 24V to 48V.