12V vs. 24V vs. 48V system in a camper

[Marco.B]

I am building out an all new electrical system for an old airstream. I’d like to keep things simple, cheap and expandable. To start, I want to build something like this
1 LiFePO4 battery from EG4
1 Growatt all-in-one inverter (5kW or 3kW)
900W of solar panels
I could use some help. First, I can see a lot of advantages of running a 48V system. Would there be any concerns of running all 48V in my camper?
Second, I’m looking at a growatt 5kW inverter all in one that runs at a 240VAC output. I’m located stateside so I want to run at 120V. Are there 5kW growatts or other comparable all in ones that output 120VAC? If not, Would I have to run a transformer for this model? Are there transformers you recommend?
Third, do all solar panels work for these voltages? Are there specific panels for 12v or 48v systems?
Lastly, do I have to run a 48V to 12V step down converter to run tail lights? Or can that all be powered by my truck’s power connection?

I’d love any advice you can give as I am new to solar and there is a steep learning curve. Thanks,
- Marco

 

[FilterGuy]

First, I can see a lot of advantages of running a 48V system. Would there be any concerns of running all 48V in my camper?

@Will Prowse has recently taken the position that systems should be either 12V or 48V. However, I still think there is room for 24V in campers.

In the last 48V camper system I designed, I ran into a few problems:

1) Availability of 48V appliances. In a camper there are several things that are nice to run directly off the 'native' DC. (Fridge, heater-blower, lights) This allows you to run them without the inverter losses. Depending on what you want to run on DC, this may or may not be a problem.
You can always use a buck-converter to get to 24V or 12V but...

2) Availability of affordable 48V buck converters with Low Voltage Disconnect. You will almost certainly have some 12V loads (and maybe even 24V loads) so you will almost certainly need a DC-DC converter. There are some nice ones out there, but if you want to have a low-voltage disconnect on them, you might have a problem finding one that is affordable. Victron makes a 9A 48-12V converter that you can parallel to get more current... but it gets expensive quickly. If you are willing to have the battery BMS be the only line of defense, this is not an issue.

3) Availability of reasonably priced alternator charging DC-DC converters. Since it is a trailor, this may not be an objective so it may not be a problem for you.

 

[Zil]

5000W? That is a mighty inverter for a RV trailer. 48V 100AH battery is a small battery for that inverter.

What Filterguy said. Plus I think home-built 48 volt dc is dangerous in a camper.

 

[John Frum]

To reiterate what @FilterGuy has said its the integration with the legacy 12VDC stuff that complicates things.
I prefer 24 volts for mobile systems with inverters larger than 2000 watts continuous.
For greater than 4000 watts continuous its time to start looking at 48 volts.

 

[Will Prowse]

I am actually doing a video on 24V RV system right now. It is more safe than 48V, but more efficient and cheaper than 12V. I personally only build 48V and higher, but 24V seems to be a good voltage for some.

 

[John Frum]

Here is a 30 amp 48 volt buck converter https://shop.pkys.com/Victron-Energ...4812-30A-Isolated-DC-DC-converter_p_7277.html
@Marco.B check the ac2dc converter in your rig to see how much amperage you need.
Also you may be able to get away with less.

 

[time2roll]

Running lights, brake lights, brakes are driven by the tow vehicle. The emergency breakaway braking system will need 12 volts and at least 3 amps per wheel.

While there are advantages of 24 and 48 volts I camp just fine with 12 volts and 2000w inverter. Can't imagine needing more unless you plan to run the air conditioner near continuous in which case you probably need 3x solar and battery.

 

[FilterGuy]

Can't imagine needing more unless you plan to run the air conditioner near continuous in which case you probably need 3x solar and battery.

My advice to the OP is the same as I tell everyone else: Do an energy audit in order to get a handle on the needs. The tool I use is this:

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

The tool is not perfect, and you may have to fill some of the slots with guesses, but it goes a long way to help understand the energy needs.

 

[CarlCruzin]

I'm in the process of putting together a 48v 10kwh system in my rv with at 4kw pure sine inverter. I picked up a 48v to 12v converter with a 100A output rating. This will power the hydraulic leveling system, and all other 12v systems. I also plan to run 1 AC unit off the inverter when needed.

 

[FilterGuy]

I picked up a 48v to 12v converter with a 100A output rating.

Link? Is there any low voltage disconnect?

 

[Firetodd]

I built a 48v 280ah battery, paired it with a MPP LV6548 inverter, and it to a sub panel in my 5th wheel. I left the rv electrical system in place, and plug the camper into the solar set up. I then added a Victron 48/12 converter to keep the existing lead acids house batteries charged. 3500 watts of panels to charge the system.

The fine people in this forum helped me with the entire build.

 

[CamoGreg]

I built a 48v 280ah battery, paired it with a MPP LV6548 inverter, and it to a sub panel in my 5th wheel. I left the rv electrical system in place, and plug the camper into the solar set up. I then added a Victron 48/12 converter to keep the existing lead acids house batteries charged. 3500 watts of panels to charge the system.

The fine people in this forum helped me with the entire build.

Well done.

I'm still in the design stages of a similar system. Leave the 12V in place, with 48V to run the AC side.

But it takes a big 5th wheel with enough roof and compartment space to have that much system.

Charge the 12V stock batteries with the AC either with the stock converter or a dedicated charger like the Victron IP22. In my case, the stock battery compartment is neither big enough or climate controlled for anything other than the original batteries. It simplifies the assembly a bit.

 

[Firetodd]

Well done.

I'm still in the design stages of a similar system. Leave the 12V in place, with 48V to the AC side.

But it takes a big 5th wheel for enough roof and compartment space to have that much system.

I put 6 350 watt panels on the roof of the 5th wheel and 4 350 panels on a patio at my lake site.

 

[CarlCruzin]

Link? Is there any low voltage disconnect?

36V 48V to 12V 100A 1200W DC DC Step Down Converter Voltage Regulator w/ACC

Wide input voltage from 30 to 60V Work for appliances from 0AMP to 100AMP automatically 100% full rated power 100% full stable output current 100% burn-in test High-efficiency up to 95% Waterproof sealed Cooling by free air convection Surface mountable 3-year warranty Over-current, over-voltage...

daygreen.com

 

[FilterGuy]

36V 48V to 12V 100A 1200W DC DC Step Down Converter Voltage Regulator w/ACC

Wide input voltage from 30 to 60V Work for appliances from 0AMP to 100AMP automatically 100% full rated power 100% full stable output current 100% burn-in test High-efficiency up to 95% Waterproof sealed Cooling by free air convection Surface mountable 3-year warranty Over-current, over-voltage...

daygreen.com

I have looked at that unit before but never bought it. How do you like it?

It does not look like it has any know of control that could be used for a LVD.

 

[12VoltInstalls]

in the design stages of a similar system. Leave the 12V in place, with 48V to run the AC side

I think that’s a good plan if you have to support ac/climate control. 12V can handle so much on just a 1200W inverter and all the 12V stuff is already there. Other than my vacuum, the fridge, and coffeemaker I don’t use 120V.
Well there’s the laptop charger and cordless tool chargers but that’s very intermittent.

My camper had 6 or 7 120V light fixtures. There’s only two left. One gets used rarely and the other might have been turned on a couple years ago.
The 12V LED stuff I installed uses milliwatts and the two bigger ceiling fixtures put out more light!

 

[CamoGreg]

I think that’s a good plan if you have to support ac/climate control. 12V can handle so much on just a 1200W inverter and all the 12V stuff is already there. Other than my vacuum, the fridge, and coffeemaker I don’t use 120V.
Well there’s the laptop charger and cordless tool chargers but that’s very intermittent.

My camper had 6 or 7 120V light fixtures. There’s only two left. One gets used rarely and the other might have been turned on a couple years ago.
The 12V LED stuff I installed uses milliwatts and the two bigger ceiling fixtures put out more light!

My wife and I have been full time in the RV the last 4 years. It's more a residence than occasional use.

The 12V system has many occasional uses. Leveling jacks, slides, break-away, brakes, power awnings, roof fans and rarely the water pump. Lights are all 12V LED and along with the furnace blower in winter, see the most consistent use of the 12V system.

Since it's parked most of the time (soon to be all of the time) 120V residential appliances get the same use as most homes. Microwave, countertop appliances, small 120V washer/dryer combo, small chest freezer, fridge, laptop, vacuum and tool battery chargers.

Heat is mostly from LPG. We use 19 KWH/day consistently through the year except for June - Aug when it's about double. Better managed we could likely get that down to 15 kwh/day and still not have to sacrifice any comfort.

It's already a great way to live. Being capable of generating most of our own power is attractive and interesting as hell.

 

[CarlCruzin]

I have looked at that unit before but never bought it. How do you like it?

It does not look like it has any know of control that could be used for a LVD.

Well, I couldn't tell you since I haven't installed it yet lol. But it looks pretty.

I'm trying to get the system installed this month