StirCrazy
Kamloops, BC, Canada
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Joined: 07/16/2003
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TurnThePage wrote:I'm very near to picking up a new travel trailer that I intend to pack with solar and LiFePO4 batteries. It's a 30A 120VAC RV. I understand the electrical wiring advantages of the higher DC voltage configuration, but what does everybody do with their 12v appliances?
I'm hoping for around 1500 watts of solar and no less than 1000Ah of 12v batteries. Is there a good reason not to stick to a 12v configuration?
you have to keep the 12V apliances but use a step down converter to run them like some one mentioned already.
my question is what do you think your going to gain by running a 48V storage setup over 12V setup? you said your not worried about inefficiencys but is the very slight increase in efficiency you gain with the lower amprage levels nd higher voltage levels between your battery and the stepdown converter worth it? on the AC side its the same thing but you can offset that by proper sized wires between your batteries and inverter.
with the money you save not buying a 48v to 12V inverter converter you could buy a 270ah battle born battery.
if I was going to do your system I would get four of the 270AH dragonfly/battle born batteries which ever you can get cheeper (who am I kidding if it was me I would just build my own but thats not the pourpose of this post) then I would get a good inverter to meet the needs of what you need to run and mount it right beside the batteries. for solar panels that is where I step the voltage up and run 24V panels in series as thats the longest wires in the setups.
in a home solar storage off grid set up I can see spending the money on a 48v set up as you are running a lot higher of an inverter output and the wires from the battery bank to the inverter would just be stupid, but 9 time out of 10 your never going to need larger than a 3000watt inverter in a rv using 2/0 cable you can handle 300amps at a distance of 10 feet, so there is some safety built into that as you should cut the distance down in half and a 3000watt inverter will draw about 250amps when running full out (plus a little for inefficiency.) on the other side a home system may be running dual 5000 watt inverters (or more) to provide 220V power and run the whole home so on that scale and size the cost difference in wire and the amount of amps involved makes it benificial.
I just don't see it in a rv set up, but thats my thought, if you have a different path of reasoning I would love to hear it as maybe I am missing somthing.
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ewarnerusa
Helena, Montana
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I've heard that a higher DC baseline can help reduce the impact of voltage sag. This can allow for skinnier wires, as mentioned. Or from another angle, a higher DC inverter won't be as negatively impacted by the voltage sag when you really draw down hard to meet a big AC load like microwave or even go for the air conditioner. But if you're not devising a way to run big loads off the battery, I can't see why you would want to add the complication since your entire camper DC system is setup for 12V.
Aspen Trail 2710BH | 470 watts of solar | 2x 6V GC batteries | 100% LED lighting | 1500W PSW inverter | MicroAir on air con | Yamaha 2400 gen
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2oldman
NM
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ewarnerusa wrote:Or from another angle, a higher DC inverter won't be as negatively impacted by the voltage sag when you really draw down hard to meet a big AC load like microwave or even go for the air conditioner. This is correct. Acid batteries and huge 12v draws don't always work so well. Not only is 4/0 cable difficult to work with, batteries and connectors will start to heat up drawing hundreds of amps over more than a few minutes.
In my opinion, 12v is not the best idea IF you regularly power large appliances with an inverter. For most RVers, I don't think this is a big issue, and 12v is just fine.
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Grit dog
Black Diamond, WA
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Stick with 12V. Series/parallel however many batteries you add and leave it at that, IMO.
This is a solution looking for a problem that doesn’t exist.
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afidel
Cleveland
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Personally I'd run the 12V stepdown converter into a 12V battery, either lithium or SLA. That way peak loads for the slide motors and compressor motor get taken up by the 12V battery and the 12V converter can just top that off. I know there are folks that team a couple of 12V stepdowns together to supply the loads, but it has to be much more stressful on the components in them than if there was a decent pool of ampacity there. Since you aren't actually using it for storage capacity a 50Ah 100A LiFePO4 would work great and they're like $160.
The big advantage of 48V is you can use a much cheaper MPPT controller since they're basically priced on output amps and 48V is 4x lower amps for the same watts. Wiring costs are also much lower since you get to drop down to wire gauges which are commonly available instead of double 0 or triple 0 cables.
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2oldman
NM
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afidel wrote:The big advantage of 48V is you can use a much cheaper MPPT controller since they're basically priced on output amps and 48V is 4x lower amps for the same watts. Yep, another advantage. My motto is "Wire handles voltage a lot easier than amperage."
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Grit dog
Black Diamond, WA
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Lol, you guys are 2funny!
How much DC current u think this feller gonna pull in a little camper.
He’s not building a data center, he’s stocking up on battery reserve for off grid camping (or he wouldn’t need all the batteries he’s planning on installing…).
This is becoming laughable. Talking 2/0 and 4/0 cables. Lol. U think he’s using the batteries to start his diesel truck 20 ft away or what?
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2oldman
NM
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Grit dog wrote:This is becoming laughable. Talking 2/0 and 4/0 cables. Lol. U think he’s using the batteries to start his diesel truck 20 ft away or what? I don't know why you're hurling insults. He's loading up on a lot of power. Have you never read the manuals for large inverters and see what cables they recommend?
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CA Traveler
The Western States
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Joined: 01/03/2004
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1500W is 125A @12V hence equipment layout is also a consideration as to much wiring voltage loss is a consideration. And the solar controller, inverter, charger and battery proximity is a factor.
All of the equipment, your intended usage and expectations and cost are also factors. Look at the entire system and various tradeoffs for what is best for you as there are many considerations besides DC voltage.
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Bob
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pianotuna
Regina, SK, Canada
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Joined: 12/18/2004
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Far better off to use 48 volts for storage.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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