Yet another solar panel question

[pmorris1274]

Hello, there. I searched the forums for over an hour, and can't find anything that fits my situation on solar panel setup.

We are not looking to mount one, we just want a portable one we can set up in our campsite to hopefully replenish the battery during the day. (our trailer only has one battery.)

I am eying a 15 watt one on Amazon, but am not certain if that will be enough to keep the battery replenished.

Can anyone recommend a certain wattage we would need as a minimum? We are not heavy users of our battery. We conserve wherever and whenever we can, but if we have to run the heater at night, we find our battery depletes much faster, and we just need a way to replenish most of the juice during the day. We are not planning on using our panel to run any appliances or anything like that.

Thanks in advance for any and all responses!

[2oldman]

JiminDenver wrote:

2oldman wrote:
Solar panels don't 'run' things.

Until this last trip I would have agreed with you. .

Agreed.. it is a fine distinction. I think many people ask that question as if RVs have grid-tie panels like houses.

RV panels' power goes into batteries which then "run" things. That's my point.

[JiminDenver]

2oldman wrote:


Solar panels don't 'run' things.

Until this last trip I would have agreed with you. However once our battery hit float, I could turn on every light, fans and even the furnace blower all on at once and wasn't able to draw down the battery. The controller upped the amps and the battery never dropped a 10th of a volt. Now our panel is a lot bigger than discussed here and we were not running the microwave or a entertainment center, still the panel kept the battery charged AND met out needs thru out the day.

There are members here that have bought several smaller panels and hinged them together like a suitcase for easier transporting and storage. I would aim for at least 100-150w.

[2oldman]

Doug33 wrote:
Is there ever an concern that a solar panel set up a ways from the TT can be stolen?

Here's a 30W panel for under $100. Could you theoretically buy several of these to get you to the wattage needed?

Concern, yes. Actual theft? Rarely. Thieves usually hang around in cities.

Theoretically, yes, but going that route will get expensive.

[2oldman]

pmorris1274 wrote:
I am eying a 15 watt one on Amazon, but am not certain if that will be enough to keep the battery replenished.
We are not planning on using our panel to run any appliances or anything like that.

Think of solar as a battery charger that runs only during a sunny day, and then only puts out 70% of its rated power for 4-5 hours. That panel is like putting a 1 amp charger on for 4 hours/day. I doubt it's going to help much.

Solar panels don't 'run' things.

[Doug33]

Is there ever an concern that a solar panel set up a ways from the TT can be stolen?

Here's a 30W panel for under $100. Could you theoretically buy several of these to get you to the wattage needed?

http://www.amazon.com/Instapark%C2%AE-Black-Mono-crystalline-charge-controller/dp/B004FOGL0K/ref=pd_sim_sbs_auto_1

[Tom_M1]

I would suggest a minimum of 75 watts. I purchased a panel last year from Solar Blvd. They have reasonable prices and shipping is not outrageous. They are selling a 75 watt panel for $93.75 plus shipping. Here's a link: 75 watt panel A 75 watt panel is light weight and easy to handle and store. You should be able to get by with wiring the panel direct to your batteries and not use a controller. Monitor your battery water levels periodically.

[Bounder94]

I also use a 230w panel, unmounted...I made a 'stand' for it that hinges off the back of the solar panel...I used bulk 10 gauge wire that looks like yellow extension cord....I made a pigtail off the back of the solar panel, about 6" long, with a female extension cord plug...my solar charge controller is mounted in a small waterproof plastic case, with a 10' cord with battery clips running out one side of the case, and a short 6" pigtail with a male extension cord plug out the other side....then I went and bought a 50' 10g heavy extension cord that I use to plug the solar panel to the charge controller....

I set it in a specific order like this: Set up solar panel in the sun, then I plug the male plug of the 50' extension cord into the female plug of the solar panel.....I hook up the battery clips to the battery bank of the RV...then I plug the male plug of the charge controller into the female plug of the 50' extension cord....and your set....

The RV stays in the shade, while the panel is sitting in the sun...I move the panel to catch the morning sun....then once around lunch for the midday sun angle, then once more in the late afternoon for evening sun...

The 230w panel charges my four 6v GC batteries to full by early afternoon....

I use this setup around the farm to charge tractor batteries out in the barn or the grain trucks, since they sit around for sooo long....when I know I am going to be wanting the tractor the next day, I will set the solar panel up and let it charge the battery the day before....I figure if I am going to spend the money on the solar set up for my RV, I might as well NOT permanently attach it to the RV....then I get more year round use of it....same with using the heavy 50' store bought extension cord, I can use it anywhere/anytime I need an extension cord...the 'system' is very versatile and multipurpose.

Your idea of a 15w panel is not a good one....go with a minimum of 130 and 230 is a good value for the buck for one panel to work with a multi-battery bank

Bounder94

[JiminDenver]

A lot depends on your needs. We are light power users, basic trailer things like lights, pump, furnace, etc. Others have TV's and satellites and inverters for their microwaves, etc. They need a lot more power to keep them charged up.

We take a 230w panel, a set of cords and a controller with us. It isn't mounted, I set it in the sun and adjust it through out the day. We could use a smaller panel but I found this one cheap on craigslist. The cool thing is all day long after the batteries hit float, if I turn on something the panel covers it without draining the batteries.

[time2roll]

Forget watts. Look at ampere rating. Isc is short circuit rating and that is what you will get on a clear day tilted at the sun.

Here is a 120 watt panel that provides 7.5 Isc amps for comparison.

Solar Cynergy 120 Watt 12 Volt Solar Panel

You may get full rating about 3 hours per day ramping up in the morning and down as the sun sets. This would be about right for a single battery and moderate use. You should also get a controller.

[hmknightnc]

Single battery recharging under light use (as you describe) 100 to 150 Watts solar is a good ball park to be in

[pmorris1274]

Thanks, Steve! That really helps!

[SteveAE]

A 15 watt solar panel will not recharge a RV battery. It will maintain your battery charge while in storage though.
If you want to replenish your battery while camping, you will need about 10 times that (150 watts).

Steve