20w coleman solar panel

[Zacvv]

Hello,

I have just purchased a 20w coleman solar panel and a charge controller. I was wondering if there are some things i should know before i chuck this on the roof? Im going to just screw it to the roof and use a stack of silicone.

Wiring ideas? Cover needed for panel?

[westend]

Zacvv wrote:
Thanks for everyones help! Ill let you in on a few photos of the trailer so you can appreciate its specialness

Bring 'em on, Zac. I have a '71 so am always into the vintage rigs.

[Zacvv]

Thanks for everyones help! Ill let you in on a few photos of the trailer so you can appreciate its specialness

[westend]

Eyetattoo wrote:

westend wrote:

Eyetattoo wrote:

Zacvv wrote:
Thats a good thing to hear i was starting to feel like i may have made a bad purchase. How much do you use your 12v system and for what things?
eye tattoo

We power our sound system during the day and usually a 21 inch LED TV. At night the TV and lights get used. I used to run the generator for 6-8 hours a day, now roughly 4 hours. I do plan on adding 1 more 20w panel so it can keep up a little better.

There is no possible way that a 20W solar module will equate with two hours of generator run time even with the smallest RV converter. You are either running the generator too long or have misjudged the amount of charge the module can deliver.

If can you state how many AH's you are using in a day, I'll retract my previous statement.

No I cant state my actual AH's, don't know how to calculate it, but I have no reason to lie. Maybe its because we camp at Pismo where we get a good 10 hours of sunlight, who knows. All I know is that the 20w panel does a great job for our usage. Once I convert to LED lights and the temps rise(which means no need to run the heater at night) at the beach I might not need to run the generator at all. I still want to add one more panel just for good measure though.

I don't think your honesty is in question. I hope you didn't get the impression that I was questioning it. I do question whether you have accurately estimated the contribution of the 20W solar panel. That's important not so much to me or even you, but may be important to someone shopping for solar modules and reading this thread or to the OP.
If someone thought that a 20W solar panel would take care of their battery charging needs and at the end of a 24 hr. cycle that battery State Of Charge (SOC) would be near 100%, they may be disappointed or feel that they were misinformed.

Maybe breaking it down a bit would help: A typical RV'er will use 40-100 AH per day off their 12V system. The OP will be at the lower end of this (maybe lower), since he doesn't have alarms, a working furnace, or an inverter. For the sake of this discussion, let's say his use is 40AH (maybe he uses a radio).
Let's also say that he has a brand new 12V marine/deep cycle battery that has a 20hr. rating of 90 AH. We need some type of battery to compare since drawing the battery below 50% SOC will limit the longevity and we need some type of threshold to compare. The threshold amount in this case means the user has 45 AH of usable power, just a bit more than the daily usage estimation.
Our user goes to the beach on a nice sunny day and parks. At the end of his first 24hr period he has used 40 AH and the 20W panel has returned 5AH back into his battery. He is now down 35AH and in the next 24 hr. period, without a generator, will draw his battery down below 50% SOC. Somewhere in this second day his battery will not be above 11V and typical 12V devices won't run. If someone leaves a light on during the first 24 hr. period, he'll be down to 11V in short order. Repeat this scenario a handful of times and a new battery will be needed.

For the sake of this discussion lets say the above is what actually happens and now the user is contemplating a new battery. Maybe he's getting smarter and buys 2 x 6V GC2 batteries this time. This allows 105-115 AH to the 50% SOC mark. If his use and solar system remains the same, he'll now be able to use his 12V system into a third day but will be at the 50% SOC threshold at the end of that time. The 20W panel will only return 5AH/daily back into the battery at the maximum.

[rbpru]

Let’s say you want to off-road and depend solely on your solar panel.

Well, there is nothing mystical here, at full power (full sun) you solar panel will deliver 20 watts or about 1 .6 amps. So if you run your water pump at 3 amps for 5 minutes I will take about 10 minute to recharge.

Let’s say you have four hours a day of full sun and at total of 3 hours of partial sun, such as shade and early or late in the day sun, at only 10 watts from your solar panel. Then you will have generated 4 x 20 = 80 watts hours plus 3 x 10 =30 watts hours for a total of 110 watts hours of sun power that day. This is not very much power.

The question is what are you going to do with this power. In an idea world you could run a 25 watt light for about 4 hours or your 36 watt water pump for 3 hours etc.

Unfortunately theory hit the cold light of reality and other factors come into play.
• The systems are only about 80% efficient so you really have only about 90 watts hours to play with.
• You are dependent on tomorrow’s sun to make up for this evening usage.
• You may have various phantom loads that draw power that you have to account for.

On the plus side, if your water pump start and stops totals 1 hr of time and your total lamp usage is about two hours you, are within your limit and you battery will be recharged; if the next day is sunny.

The question in your case is whether it is worth the effort to mount the system or not. Keep in mind that a shady camp spot will cut into you solar output, unless you can move the panel into the sun during the day.

Some battery dependent people buy a bigger solar panel and switch to LED replacement lamps.

When my wife and I are battery bound for a few days we drag out the camping lanterns and othet gear to minimize our battery load until we can get shore power.

[Eyetattoo]

westend wrote:

Eyetattoo wrote:

Zacvv wrote:
Thats a good thing to hear i was starting to feel like i may have made a bad purchase. How much do you use your 12v system and for what things?
eye tattoo

We power our sound system during the day and usually a 21 inch LED TV. At night the TV and lights get used. I used to run the generator for 6-8 hours a day, now roughly 4 hours. I do plan on adding 1 more 20w panel so it can keep up a little better.

There is no possible way that a 20W solar module will equate with two hours of generator run time even with the smallest RV converter. You are either running the generator too long or have misjudged the amount of charge the module can deliver.

If can you state how many AH's you are using in a day, I'll retract my previous statement.

No I cant state my actual AH's, don't know how to calculate it, but I have no reason to lie. Maybe its because we camp at Pismo where we get a good 10 hours of sunlight, who knows. All I know is that the 20w panel does a great job for our usage. Once I convert to LED lights and the temps rise(which means no need to run the heater at night) at the beach I might not need to run the generator at all. I still want to add one more panel just for good measure though.

[westend]

Zacvv wrote:
My trailer has cost me just over 1000 dollars once i have renovated the thing fully and bought new batteries. If i spend 80 dollars on giving me a little extra juice when im in the bush why not.
If i switch my lights to LED im sure this panel will do me wonders. Plus in the area we camp its the sunniest spot in bc

I don't think anyone that's posted has an issue with your intentions about using solar power. A lot of us have migrated towards it and find it's a great deal. Batteries aren't cheap and a small solar installation will keep them in top shape.

Yeah, LED lighting will save a lot of power and are an inexpensive retrofit.

I would suggest that you use the energy audit spread sheet posted by Pianotuna and do some math to find out what your needs will be. 20W won't take care of your needs but it's certainly a start. Forum member BFL13 lives in your neck of the woods and is always looking for good deals on modules and gear. Maybe a PM to him would give you a vendor name with good pricing.

Good luck with your solar installation!

[hedge]

I know they're now branded as coleman but I think it's the same Sunforce stuff that they used to have. It's really not very good quality.

I think you'd be wiser to return it and if you want to buy it from CT wait until they have the 40 or 60w panels on sale, they come with the controller.

[JiminDenver]

Thank you.

The others have explained how much power it produces and on that budget I am not sure how much more could be bought. It might work out well enough and if it doesn't, you are not into it for a lot. I'm not one to follow the recommended road often and yet somehow it works out. I hope the same for you.

[Zacvv]

My trailer has cost me just over 1000 dollars once i have renovated the thing fully and bought new batteries. If i spend 80 dollars on giving me a little extra juice when im in the bush why not.
If i switch my lights to LED im sure this panel will do me wonders. Plus in the area we camp its the sunniest spot in bc

[Zacvv]

The 20w panel was on sale at canadian tire here in canada for 64.95 thats half price and the controller was 20 dollars.

[JiminDenver]

If I may ask, how much do they get for a 20w panel and controller? I've thought of getting one to keep the batteries from discharging over the winter. It wont be a issue once I install the real system but I'm still curious.

[Alfred622]

Agree with Westend. Good advice.

[pianotuna]

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

[westend]

Eyetattoo wrote:

Zacvv wrote:
Thats a good thing to hear i was starting to feel like i may have made a bad purchase. How much do you use your 12v system and for what things?
eye tattoo

We power our sound system during the day and usually a 21 inch LED TV. At night the TV and lights get used. I used to run the generator for 6-8 hours a day, now roughly 4 hours. I do plan on adding 1 more 20w panel so it can keep up a little better.

There is no possible way that a 20W solar module will equate with two hours of generator run time even with the smallest RV converter. You are either running the generator too long or have misjudged the amount of charge the module can deliver.

If can you state how many AH's you are using in a day, I'll retract my previous statement.