Small solar charger system...

[oakmandan]

I am interested in using a basic solar panel with my camper to charge one or two 12V batteries. I would want to be able to run the water pump, a light or two and a 12V fan. Any suggestions of how to and what equipment I would need ?

Thanks, Dan

[oakmandan]

Thanks for all the info !

[JiminDenver]

We are generator free with 230w of solar and a 345ah battery bank. To watch us use the rig you would think we are plugged in and we are. We just happen to bring our own 12v grid with us.

No longer do we use the rig like a hard sided tent with a bathroom. Using HF puck lights, setting the stat at 50 and only on nights in the 30s or below and watching a tiny TV or portable DVD player. Now we light er up end to end with LEDs, set the stat to a comfortable level day and night and watch a big flat screen with a tailgater dish set up.

So solar is really nice if you know your needs, conserve where you can, have enough battery for a few days of clouds and enough solar to bring it back up quickly. Oh yeah some kind of back up is nice too.

[Almot]

EsoxLucius wrote:
Handy Bob isn't very trusting, but I don't know if I can trust anyone who can't figure out an IPN-ProRemote either. His message for the most part is correct.

Correct in essence, not in details. And easier, more interesting to read when you're not much into pure engineering. He touched all the important issues - shading, wires, tilt, monitoring. After his blog all this should be clarified through sources like Jack Mayer, or this forum 🙂

[EsoxLucius]

Handy Bob isn't very trusting, but I don't know if I can trust anyone who can't figure out an IPN-ProRemote either. His message for the most part is correct. He just makes receiving it difficult. Jack Mayer's message is received a little easier. http://www.jackdanmayer.com/rv_electrical_and_solar.htm

[2oldman]

I can meet my needs (and then some) with 800w, but not on 4 batteries with 3 days of clouds.

[Almot]

pianotuna wrote:
Hi Almot,

Hi, eliminate air conditioner use and almost any 400 watt solar system would meet full time needs. I find his page mostly a (needless) rant.

I meet mine with 256 watts.

Don't touch Bob 🙂 ... Yes, a useful advice is scattered over many pages of rant on his blog. The Golden Rules in your link earlier are a better, more comprehensive and condensed read, with fewer extremes.

Yes, 400W will meet your needs including a microwave, and 256W will almost meet them with MW. There are necessities like heating, refrigeration, ventilation in hot weather, cooking - none of them requires high current or 120V. And then there are extras like MW, vacuum, entertainment etc, this is a slippery slope as there is no end to this list. The only reason why I bought more than 300W was for future 12V fridge.

[pianotuna]

Hi Almot,

Hi, eliminate air conditioner use and almost any 400 watt solar system would meet full time needs. I find his page mostly a (needless) rant.

I meet mine with 256 watts.

I aimed at 1% or less myself and used a #10 prewire, which is another reason I went MPPT.

[Almot]

pianotuna wrote:
Hi barntt,

No, so long as the wire is able to legally carry the number of amps and is using a PWM controller voltage drop is a NON factor. That's just one of the mistakes at the page you suggested folks read.

If it is MPPT then wire size is important and should be as big as can be accommodated with the shortest possible run.

Handy Bob tends to err on the side of caution. Still, he is living generator free, one of very few solar users that can.

Yes, with PWM the wire size from panel doesn't matter as long as the voltage on the battery end is over 15V, and as long as the wire ampacity is adequate for the current.

No, with MPPT it doesn't have to be the thickest possible and the shortest possible cable run from the panel. When doing calculations for my 490W system, I found that at 60V that despite pretty long 70ft total wire run from panel, the difference between wire gauge 10 and gauge 8 was 0.7% of power loss at the very peak (which happens less than 1/3 of the time, daily). This is roughly 0.2 AH or 2.4W loss daily. With MPPT it's all about lost watts, nothing else. Considering much easier installation with #10, and the fact that people have 750W system with #10 wire, the choice was obvious.

Yes, wire from controller to battery is very important, there should be no more than 1%-2% voltage loss.

[Almot]

oakmandan wrote:
I am interested in using a basic solar panel with my camper to charge one or two 12V batteries. I would want to be able to run the water pump, a light or two and a 12V fan. Any suggestions of how to and what equipment I would need ?

Will see if my brains aren't sleeping yet...

Water pump: 10A? @20 minutes a day = 3 AH
Light: LED? You should go LED if you go solar. One light 4 hours = 2 AH
12V fan at medium speed 2A, 12 hours = 24 AH.

As you can see, a lot depends on how often you run the fan.

No radio? No 12V circuits in propane fridge? I've seen some minimalists, but wouldn't it be more sensible to use a hand pump on a 5 gallon jar in this case, rather than running a 12V pump, and save some AH for a 2nd light or a radio? 🙂

OK, total 29 AH = 100W-120W flat panel approximately. Make it 140W to compensate for battery losses. With 10A MPPT controller and #12 wire. If you are willing to mess with titled panel, 120W should do.

Like somebody noted, on a weekend trip you can just forget about solar and come back with 50% discharged battery after 2 days.

[pianotuna]

Hi barntt,

No, so long as the wire is able to legally carry the number of amps and is using a PWM controller voltage drop is a NON factor. That's just one of the mistakes at the page you suggested folks read.

If it is MPPT then wire size is important and should be as big as can be accommodated with the shortest possible run.

Large wire and short runs are an advantage from the controller to the battery bank.

The trimetric doesn't measure as well as the Victron gauge, and is more costly. I don't use an amp-hour counter myself.

[barntt]

Wow you mean somebody did a study on this? Sorry just funning ya. Not looking to have a argument here only trying to help the ones who are unsure about a DC system. Put a Trimetric 2025 or 2025 RV on your system it will tell you if the batteries are in shape or just surviving. Just look at the average system a lot of people don't know and just install from the instructions. From what I have observed very few systems are using large enough wire for getting the volts that are available from the panels to the charge controller and then to the batteries. The equipment is installed to far apart and the wires to light to get the batteries full. Figure your wire losses and voltage drop Bigger is better when choosing wires. It will be a real eye opener. Keep it short and as close to the batteries as possible. Really the only monitor you need to install in the coach area is the Trimetic meter and keep that away from a heated area (Fridge)if you can. Put everything else as close to the batteries as possible but out of the gasses from the batteries, don't want that corrosive stuff on the electronics. One more thing cheaper charge controllers are not getting high enough voltage to the batteries to TOP them off, that means you will replace your batteries more often and get less out of your system. Keeping everything as close as possible will help with that. 400 watts of panels and 4 Six volt batteries are plenty for the average boondocker some want more some less. Always fuse protect your systems. My money comes the hard way and I want the most bang for my buck. Just trying to help here. Don't kill the messenger. Have a great Day! One more thing use a Hydrometer for checking the specific gravity of the cells and a chart will tell you the health of your batteries.

[pianotuna]

I find this link pretty much says it all with the exception of balanced wiring for battery banks. It is a tiny bit dated. http://www.jackdanmayer.com/rv_electrical_and_solar.htm#The%20Golden%20Rules

[pianotuna]

Hi barntt,

Please support your statement. Which study shows this to be true?

barntt wrote:
97% of the solar systems are under wired

[time2roll]

tplife wrote:
12V AGM batteries will provide you with more Ah in a smaller space without the many drawbacks of lead-acid batteries. Rock My RV recently showed their solar/power setup using a pair of Group 24 Optima AGM Batteries like the one we use for a "house battery", sans panels...

Might need to review the Ah specs on that Optima vs wet cell battery.
Most AGM are actually about 10% less Ah rated and Optima is 1/3 less.