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Old 03-18-2018, 09:36 AM   #1
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Convert 12v to 48v system

I want to run the ac with a 48v to 120ac inverter.

Is it worth it to upgrade to a 48volt system?

I 'll have to get a 12volt converter to run the 12v system.
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Old 03-18-2018, 09:44 AM   #2
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No. Now, we need more info for you to get a helpful response. Are you going to install a very large (2kw) solar array using large 46v panels? Multiple inverters? How about your battery bank? 1,200ah or more lithium??
More details needed.
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Old 03-18-2018, 09:46 AM   #3
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Can it be done? Yes.
Is it worth it? From a ROI perspective - no. Outside of ROI - only you can decide.
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Old 03-18-2018, 06:37 PM   #4
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Originally Posted by vsheetz View Post
Can it be done? Yes.
Is it worth it? From a ROI perspective - no. Outside of ROI - only you can decide.
here ^^.

on my coach, there is too much bling linked to 12v - alternator 12v charges chassis battery and also house battery; genset outputs 120vac but also 8a 12vdc to house battery... if i upgrade to 48v, all of these 12v stuff wouldn't function.

i have been inverting from 12v to 120v for years with a happy result, i have seen sometimes my inverter drawing 220a at 12v. does my wire size impaired the efficiency? would 48v to 120v ease out of wire burden? theoretically yes, but we live in a real world there might be way many bigger impairing items dwarfing the wire size and voltage disparity.

now, if you are building a trailer electric system from scratch, let's say just a shell nothing in it, yes, you can go for 48v. just as vince said, only you can tell.
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Old 03-18-2018, 07:29 PM   #5
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Originally Posted by ctarmor View Post
I want to run the ac with a 48v to 120ac inverter.

Is it worth it to upgrade to a 48volt system?

I 'll have to get a 12volt converter to run the 12v system.


No!
The only thing 48-120V buys you is savings on wire size between your battery bank and inverter. That lead should be as short as possible anyway.

If you have a battery and solar bank capable of a sustained draw of 150+ Amps for hours, go for it.
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Old 03-19-2018, 07:40 AM   #6
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It is very uncommon to have a 48 volt input converter in a RV. Some bus conversions have them because the chassis was designed for 48v. Stationary home solar systems are often 48v.

1. Wire sizes will be larger gauge number (smaller) due to higher voltage.

2. There are 48 volt inverters out that are a few percentage points more efficient than their 12 volt counterpoints. But with an added 48v to 12v converter your lose some energy (less than 100%) for anything 12v powered.

You can get higher voltage/wattage alternator or install a second alternator (48v) on your engine, depending on your unit. It is all a question of time and money.

It would be much easier/less costly to design around a 12v system. It will not be inexpensive however.

We can help your here on this forum. But respectfully we need some more information.

1. Make, model and year of your RV.

2. How many air conditioners/heat pumps are involved?

3. Details of your existing battery bank. Plan on some very serious upgrade here several thousands of dollars.

4. How many hours in a day do you plan on operating your cooling system. Are you a weekender in RV parks, dry camping with no hook-up, months alone in the desert? Tell us a little about how you would like to use your RV.

5. Existing generator wattage? Gas, propane or diesel?

6. Ever think about a pair of small Honda generators for your RV? Assuming you do not have an existing generator.

7. Is a solar charging system an option to replace energy consumed by cooling system. If so start thing about maxing out PV (solar) panels on the roof. Again think several thousands of dollars more.

Let us help you. I will not bite you.

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Old 03-19-2018, 07:55 AM   #7
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Your older posts lead me to believe you have a Sprinter based RV.

You aren't going to have a lot of roof space for solar needed to recharge the huge battery bank that will be needed to run ACs for any substantial time.

Where would you put all of the batteries ?
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Old 03-19-2018, 08:59 AM   #8
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Quiet around here, I think we scared off the OP, boys!
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Old 03-19-2018, 02:09 PM   #9
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Originally Posted by ctarmor View Post
I want to run the ac with a 48v to 120ac inverter.

Is it worth it to upgrade to a 48volt system?

I 'll have to get a 12volt converter to run the 12v system.

Some people have done this with new LiPo4 $$$$$$$ and other have done it with lithium packs from Nissan Leaf or Chev Volt.

Also want to look into mini split AC which is far more efficient than roof top units.
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Old 03-19-2018, 02:29 PM   #10
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Some people have done this with new LiPo4 $$$$$$$ and other have done it with lithium packs from Nissan Leaf or Chev Volt.
Yes, folks have and here is a recent one that was in a 48v golf cart. "Fire"

Trailer Fire - need some help please. - HDT - Escapees Discussion Forum
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Old 03-20-2018, 12:55 PM   #11
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Higher voltage from solar panels to a 48 V battery suite also requires a smaller amperage MPPt.
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Old 04-16-2018, 01:50 PM   #12
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Real benefit to 48V is a 48v AC

It seems to me that the primary benefit of 48V for an RV would be to use one of these for AC: Solar Electricity | Solar Powered Air Conditioner | Green Energy Innovations

They can be a pain to install in an RV, but the key benefits of a mini-split are:

A) About twice as efficient as a rooftop AC unit
B) Frees up roof for more solar
C) Heat pump in a mini-split can be used down to about zero, whereas a roof-top heat pump only works to about 40 degrees.


As noted above, 48v is more efficient than 12v both for charging from solar and converting to 110v, which is why it is typically done that way for stand alone solar homes. But it seems that the real benefit of 48V for RV is the ability to do AC via solar, as it isn't really practical to run a rooftop AC using rooftop solar.

I supposed you can also do a 110V mini split in an rv, but then you lose efficiencies converting from 12v to 110v, so to really maximize efficiency, then 48v mini-split seems to be the best.
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Old 04-17-2018, 10:43 AM   #13
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As noted above, our 5th wheel utilizes a 48 V nominal battery bank. Power comes from 1400 W panel array at 90 V. This is 16 A at 90 V and would be 116 A at 12 V nominal. The controller converts to 48 V or about 30 A.

Power goes to cabin via 4kW PSWI and a 508 W 48 V to 12 V converter.

We have “harvested” at rates greater than 1400 W, in mid-summer and above 9000’ elevation. We can run air conditioner for 4 hours as combination of solar and battery bank. Generally just run it for an hour at dusk. We have looked at mini-split air conditioners but decided to just avoid really hot areas.

We do have a 1 kW generator which has only been used to exercise for 30 minutes or so every few months. We have only hooked the fifth wheel to line power once in several years and that was when we left the rig in an RV Park for four days; the only RV Park we have utilized in US in a few years.

Both our 5th. Wheel and Roadtrek are set to run line power through battery charger to LFP banks. We and others have had sad results with dirty power in Mexico. Battery charger to battery is most effaciousv from 60 to 200V.
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Old 04-26-2018, 02:20 AM   #14
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I am actually a very big fan of 48 volt systems, in fact it is the only type we install for new setups.

IMHO, the only reason to stay with 12 volts for a higher power setup is if you have already made a major investment in a 12 volt inverter.

For someone doing it themselves, I might suggest using 24 volts as there are more components around (since it is common in semi trucks and boats).

Not a single one of our customers has ever regretted having a 48 volt system vs a 12 volt system, and a good 48 - 13 volt converter solves a lot of problems with 12 volt compressor refrigerators and diesel heaters.
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