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Discussion Starter #1
When talking about a power system, I've seen several systems that utilize a 110V AC and 12V DC system. That seems to be the most common.

I spent time talking to a master electrician today who recommended a 48V system. (See image)


He said to run everything through the AC system so that I don't have to worry about powering in DC at all. DC would just be used to collect and store energy.
I was so stuck on having a 12V DC system from all of the RV websites that it was hard to hear him out.

I am about to start wiring and want to "do it right".
What do you guys think about the above plan?
Does it work for an RV situation?
 

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I don't know about a 48v system or how that changes anything but you want to run as little as possible off the 110 system because there is a lot lost during conversion to 110 as I've understood. Your power storage is dc so you want to make everything dc if possible because that's the most efficient. Your lights and fridge should be 12V. An AC fridge uses twice as many amps. I think what he isn't realizing is that shore power isn't guaranteed. He is assuming that you'll always be able to plug in.

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Discussion Starter #4
Aren't you missing any benefit of charging from your alternator in this setup? That's always around whereas shore power is fleeting.
He didn't add that because the focus is on wether or not 48V is desirable (over 12V), and should most/all electronics be running on AC.

... there is a lot lost during conversion to 110 as I've understood....
An AC fridge uses twice as many amps. I think what he isn't realizing is that shore power isn't guaranteed. He is assuming that you'll always be able to plug in.
Good points...

12V converting to 110V has better efficiency than 48V to 110V? I'm interested to read more about that.

A thought: If you say all/most of my stuff should run off of DC, then is there any reason not to use 48V? I'm guessing here, but it sounds like the efficiency loss would be negligible since very little would run on AC during boondocking.
 

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Sounds like "Sparky" wants to make up a complicated, expensive system to solve a non-existent problem. Why would you have to worry about powering anything with 12v? I just got rid of my 110vac fridge and now I only use the inverter a few minutes a day (at most) to power my microwave.

Is he a politician also? ;)
 

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There is no point in 48v. The army uses it but you have no reason to. You'll have to size down to 12v to use the power and lose power at that point. Put everything you can on 12v. Unless there is something I don't know, that electrician doesn't know what he is talking about in regards to wiring a system for a van.

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It would be a good way to waste a bunch of power doing conversion and to waste a bunch of money too. On this forum it seems like someone is sure to do it as a way to do both! Advantage? None really as 12V appliances are available, cheap, frugal in their use of the limited power from solar and efficient in terms of space and wiring. You could convert the van to 48 volts too. Wow what a money, time, and resource waster that would be. (sarcasm meant for your electrician not you)
On the other hand 48 volts and a few sticks of 6010 or 7018 rod and you can weld! You can weld right? Perhaps the electrician can? Use a #10 mask.
 

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The only reason I see for a 48V system would be if you were running a very large inverter, over 3500W output - for such an inverter you would need more voltage to keep the input current down.

Otherwise, unless you have a very specific reason for 48V, such as running telco equipment or military gear, it just adds complexity. If your inverter is less than about 2000W, just run 12V. Then run your LED lights and fridge on 12VDC, and set up a charging path from the alternator to the battery for the times you aren't on shore power. Plus, having the alternator path allows you to do things like run the inverter while running down the road, which means you can do things like run an oven during travel, thus saving battery power for when you aren't running.
 

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I should be the last one to comment on this because I know so little about power systems... but from everything I've been reading... the 48V system will probably become the desired route for RV's in the future. One benefit supposedly, is the ability to run air conditioning successfully on battery power... for hours... not minutes.

Off grid homes have been using 48V systems with great success and it is starting to find it's way into the RV world.
Again, I have very little electrical knowledge, but I've been reading that the 48V system will be the answer for finally being able to run high powered appliances like air conditioners, successfully and efficiently in RV's.

I personally wish I had more time to investigate ... but it's a new thing and only just beginning to be used... I need to use my van for my business, and we're already about 2 months behind schedule.

I recently watched a video that the Fit RV posted about "What is new in the RV industry". I think it was a company named Advanced RV... or something like that. They were experimenting with a 48V system and lithium batteries, and supposedly ran the air conditioning for 7 hours... and still had not depleted their batteries... that's pretty impressive!!
 

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For larger systems 48v can make sense for a number of reasons, including what wowbagger mentions above. These include: smaller wire gauge for DC, cheaper inverter options for same power, possibility to use EV battery systems more directly. It depends if you have a lot of 12V loads, then you'll need to convert down again. If you are dealing mostly with AC with high power demands then it might be worthwhile.

David Dixon has documented a build using a Chevy Volt battery pack for his heavy duty truck RV, but that's much bigger than a van conversion.

Here's the most recent presentation I've seen, but he has done others over the past few years.

http://eastcoasthdtrally.com/wp-content/uploads/2017/04/ECR-2017-Lithium-Battery-System.pdf
 

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I'd read some articles about all the hoops Toyota had to go through to run air conditioning off of batteries on the Prius. It rivals the complexity of the drivetrain. I'm sure AC in EV's is just as complex. I'm hoping that some of this technology will trickle down to RVs.

To me RV air conditioning is stuck in the stone-age. None of the added efficiencies of household or more modern mobile air conditioning. Worst of both worlds.

As for this electrician he's probably a residential or industrial electrician, and you design what you know. For an off-grid residence with all AC appliances and higher loads, it makes some sense. Not for a near-term van conversion, however.
 

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For many years the rail and locomotive industry generated, stored and used 32 volts. Remote farms had it for their radios too. Some boats have 32 volt systems today. There was lots of 32 volt equipment available in the 70’s when we installed a wind power system at our remote home in Vermont. In fact 32 volt wind generators made by Jacobs were all over the mid-west left from before the REA brought them power. Many were free for taking them down in the 70’s. Inverters were essentially non-existant so one used a very inefficient motor-generator to change voltage. Why 32 volts is not a better option now eludes me as it is safer than 48 volts and usually sufficient to reduce current losses and wire sizes. 8 volt golf cart batteries are readily available now too so 32 volts is four of them. I wouldn’t be surprised to find appliances still available for it as well. Why don’t one of you do a 32 volt system and report back? BTW we opted for a new Dunlite 114 Volt DC (19-6 volters).
 

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I would think they would use 2/12v batteries not 1/24v but I really don't know. Cost is no object in the military.
 

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And the weight of 8 6v fld batteries would be 480lbs and take up 4sqf of floor space with 800 ah at a cost of $700. 4 12v sla would be 260lbs takeup 2.25sqf with 400ah at a cost of $1150.
 

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Discussion Starter #16
Response on the electrician: You're all right - While being a master electrician, he only has experience setting up off-grid systems for businesses but not mobile systems.

Seems like the loss in conversion from 48V to 12V or from 48V to 110V would not be worth the extra cost and equipment (weight). I made this post to discover these good points you guys bring up. I knew there was a valid reason that 48V felt wrong to me but couldn't put my finger on it.

While I agree that 48V systems will make their way into the RV world, time limitations and cost are preventing me from being the pathfinder on that one (sorry RD, no 32V system for me!). I'll just resolve myself to contributing to the RV world in my sound deadening research. :)
With that said, I am looking hard into lithium for the weight savings and lifespan advantages.

I started drawing up a new plan based on everyone's critique and realized that it was pretty much identical to Gary's buildagreenrv so I'll just provide the link to that.

Does Gary or anyone else have any recommended changes to his plan? Any new mods/designs/improvements that I should make to the ground he already plowed?

Thanks for the great info, everyone!
 

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Response on the electrician: You're all right - While being a master electrician, he only has experience setting up off-grid systems for businesses but not mobile systems.

Seems like the loss in conversion from 48V to 12V or from 48V to 110V would not be worth the extra cost and equipment (weight). I made this post to discover these good points you guys bring up. I knew there was a valid reason that 48V felt wrong to me but couldn't put my finger on it.

While I agree that 48V systems will make their way into the RV world, time limitations and cost are preventing me from being the pathfinder on that one (sorry RD, no 32V system for me!). I'll just resolve myself to contributing to the RV world in my sound deadening research. :)
With that said, I am looking hard into lithium for the weight savings and lifespan advantages.

I started drawing up a new plan based on everyone's critique and realized that it was pretty much identical to Gary's buildagreenrv so I'll just provide the link to that.

Does Gary or anyone else have any recommended changes to his plan? Any new mods/designs/improvements that I should make to the ground he already plowed?

Thanks for the great info, everyone!
I basically copied Gary's system. He's been a big help for me. If you look in http://www.promasterforum.com/forum/showthread.php?t=66666/ thread to see my schematic. I just changed Gary's up a little.



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Thanks, I remember this post. I'll read it again with fresh eyes.
Also check out this post http://www.promasterforum.com/forum/showthread.php?t=64610 it helped me with hooking up my inverter. You'll see how I arrived at my inverter setup around post 45. I did hook mine up a little different than Gary. My inverter/charger will still have a warranty because I hooked it up the way the manufacturer intends (by not cutting off the power cord).

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