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Noob solar set up/controller questions

OUBob

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Oct 4, 2021
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Hello,

I'm new to the solar experience, looking to utilize solar on an rv using a few components I already have and I am looking for advice on the remaining equipment I will need, with a goal of deleting the generator.

I have 2 Trina 250w panels, putting out 37.4v and a 1500w continuous Schumacher inverter. I'm hoping to use the panels along with batteries to cover my needs for a half dozen or so weekends a year.

I need to identify a solar charge controller that can take the panel voltage and charge 12v batteries. I was given an El cheapo eBay controller, but it auto selects parameters for a 24v system, I assume due to the voltage coming from the panels. I may not be interpreting the Engrish on the "manual" completely.

I'm also in the air on battery selection, lead acid vs LiPO. I understand if I go lithium, I will need a BMS for safety concerns at a minimum. I expect very low demand, basically I just want to maintain 12v to the fridge and furnace, with enough juice left over to run the furnace fan at night. Would it be easier to just stick with LA and keep them on a trickle charger when not in use? This will not be a permanently installed system initially, I'm not willing to poke holes in the roof yet.

Thanks,
Bob
 
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I'm not willing to poke holes in the roof yet.
I’m never willing to poke holes in a roof.

Don’t poke holes in the roof.

To support panels, make a “roof-rack” system that is side-mounted.

For wiring, buy rooftop dual-wire ‘gland’ fixtures- but side mount that with a drip-loop.

Problem: fridge.
Is that a 12V/propane fridge? Running that on 12V will either be almost a deal breaker or a failure (you pick).
If it’s a true 12V compressor refrigerator you’ll want all of the 500W panels- same with a 120V fridge- to do what you want. Add the furnace fan and you may be marginal with 300Ah of usable fla battery or 300Ah of lifepo. For the furnace I’d see about getting two more panels for 1000W total. That will insure quicker recovery at sunup. And 300Ah I’m guessing is too little for colder temps/longer furnace use.

Those aren’t scientific conclusions- just wild hat guesses. Cuz I don’t know the exact consumption you’ll have.
 
Fridge, furnace and water heater bill all be run on propane, just need 12v for the igniter. I'll be using the rv primary in the summer/fall and only spend time in it for sleeping.
 
Well I operated on 400W all summer with an electric fridge. So ther than furnace use (fan: 8amps?) it’s reasonable to assume that you have enough power and storage.

Is the schumaker inverter a true sine wave inverter?
Modified sine wave inverters gave me a lesson a couple times- right in the wallet when I replaced things much more expensive than a proper true sine wave inverter would have cost at the time.
I run a 1200W pure sine 24/7 currently

FWIW 400W doesn’t or just barely works out on paper for me.
But in actual use it worked fantastic all summer. I need to bump in two more 100W panels it seems. It’s still ok but I’m sometimes averaging .1-.2V lower in the AM with shorter light periods and I have the two panels. I don’t have heat that requires a fan, but I’m going to get the RV furnace going this fall just to see what it does. Experiments you see…
 
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The Schumacher is not PSW. Sounds like this experiment may be dead. Replacing stuff sounds both expensive and unsafe.

But just for poops n grins, what kind of charge controller would I be looking at to run a 12v battery system off of the 37.4v panels?
 
I used a windyNation PL30 pwm controller for several years successfully. While it does appear to be a ‘clone’ and is much higher priced (or was it cloned?) than “similar” units it has good reviews, I used it long enough to be confident in it, and windy support has been quick to respond when I thought I had problems (I actually didn’t after learning from the responses).

There’s very good controllers in the $350+ range, but for $85 to $200ish mppt’s like epever can be had. (Not a renogy fan due to numbers of failures reported and support concerns)

Those are two entry level SCCs that are more expensive than others but seem to provide excellent performance and longevity in comparison.

My ‘last lesson’ in modified sine inverters was a crt desktop monitor that was $289 to replace and I could buy the smallish true sine inverter I needed for $250ish and didn’t. I had cooked a couple other things previously, too, but I kept lying to myself like that the drill was just dirty and such…
I don’t know where it is but I still have an old old statpower 400 or 500W msw inverter somewhere. It runs a soldering iron and incandescent bulbs fine; not big enough for the coffeemaker. Some wall warts worked, others just stopped without even any smoke and never worked again.
I even knew better but did it anyways. >sigh<

Cheap inverters: stay away. Except that the 1200W Giandel true sine I’ve had for over three years is still going strong, has started every fridge I’ve plugged into it, and runs my ?9A shop vac fine. I buffed out a canoe paint job for well over an hour this summer, like 6-7A, and it never faltered even though the fridge was cycling on and off at the same time and I was charging a 20V cordless tool battery (fridge is 900ish watts startup for a sec, 60-80W running).
 
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Does that Epever allow charging a 12v battery off of a 36v panel?
 
The PWM controller is your issue here. Those are pretty basic and assume that the power in and the power out are the same. Jump to any MPPT controller and you'll get better use of your panels AND it should be able to take All-The-Volts* and put them to a 12v battery.

*Read the manual of your charge controller, it'll tell you what the voltage and wattage range for 12v is.
 
The PWM controller is your issue here.
I have run 2S 100W panels into the WN P30L and it will output/charge at 12V. Basically it makes 13.2V+ when 2P would be stupid like 10VOC. Yes, on nice sunny winter days you don’t get some watts, but it seemed to help with the typical winter semi-overcast- making a few amps at 13/14V where 2P was not really making anything.

With mppt, it “sees” the series voltage usually 38-40V and the amps - and outputs the 13.x to 16V at higher amps which is what your battery needs to take a charge (or 14V-ish if lfp batteries).
 
Yes

Epever has a good rep

Other ones are cheaper or the same price or more and don’t have a good rep

I bought the epever on will prowse’ video recommendation. I don’t regret it.
 
The good victron etc brands, top end stuff are reputed to be better but epever so far so good.
 
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