36 volt solar panel

[Oneleggedcowboy]

Hello all!   I had my purchase and understanding all lined up for my purchase of a 200 watt Eco Worthy system for my truck camper. Then I went to dinner a a friends house and in his shop he had a stack of solar panels. I did not have my glasses so he read the info on the back of the panels to me. The come off a solar farm that his son works at and they have problems. Like a stripped out mounting bolt or a broken cord on the junction box. Easily fixed things but they repack them and do no repairs then trow them into a aluminu recycle bin. It looks like they are 245 watts and 36 volt. Remember no glasses so I need to go back and write the specs down. My question is can I use this on my truck camper with my 12 volt marine batteries? I need to do this as cheaply as possible. Can I get a PWM controller? ?

 

[jimindenver]

It is a grid tie panel and yes you can use it on your battery. You have to have a MPPT controller to convert the higher voltage down to what your battery needs. The least expensive one that will work with that panel is from Eco-worthy for $102 shipped. It's how I made my first systems and they worked great.

You need a digital meter to check the voltage and short circuit amps to make sure the panels put out what they should. At 245w they may put out 10a or better so a 20a meter may be in order.

 

[sushidog]

Yes you can use it but must use an MPPT controller to convert the 36v output to 12v (at 3 times the amps). If on a budget you might want to look at a tracer MPPT controller. Just be sure you get one big enough for the number of panels you will be using.

Chip

 

[Oneleggedcowboy]

Thanks Chip but a MPPT controller would cost as much as a complete cheap PWM system from Renology or almost as much wouldn't it?

 

[jimindenver]

Ahhh there is the rub. get the panels cheap enough to afford the MPPT controller and they make a great system that is more powerful than the kit. The Eco-worthy 20a MPPT controller is $102 shipped, and you can catch them on ebay for as little as $85 in a auction on ebay. The Tracer can be had for not much more, especially if you get one of original versions from last year.

On the other hand IF the kit is enough power to take care of you, it is a much simpler solution than figuring out everything needed to hook up a panel from scratch.

 

[Oneleggedcowboy]

Jim Denver could you post a link please for the eco worthy mppt? Is it the yellow and black color 20 amp one? What would this 245 watt panel be equal to? I was looking at a 200 watt system with a PWM controller so the max would have been about 10 watts and I think according to the advertising I would have on a sunny day gotten about 60 amp hours back into my batteries. Would the 245 with 36 volts make a lot more amp hours? I like my microvave and drip coffee and TV with booster.

 

[Oneleggedcowboy]

I have no problem hooking the wires to the conttoller and then to the batteries etc. I can figure that out. How many amps as a swag estimate do you think I would get Jimindenver? A hundred bucks for the Eco MPPT controller, $20 for wires, I can make the mounts for the panel. So $120 for a kick butt system. Do I need a battery temperature sensor?

 

[jimindenver]

The Eco-worthy controller is here

http://www.eco-worthy.com/catalog/worthy-mppt-solar-charge-controller-12v24v-p-182.html

This is the newest model in a auction. I have seen them going for $85 including shipping.

http://www.ebay.com/itm/MPPT-20A-12...471?pt=LH_DefaultDomain_2&hash=item3f5004bd0f

I had a pair of 245w panels that I used with a pair of these Eco-worthy controllers. Each panel set up was good for roughly 16-17a in good light. I sold those to people installing them on vans for $500 each.

You will need a few other things to install including wire. I used MC4 solar cable with the connectors on it. A 50 ft run was around $30 shipped off ebay.

 

[Oneleggedcowboy]

That's got it pretty much lined up Jim. You are being very helpful. I found some 10 gauge cables for $20 on ebay that are long enough with the solar connectors already attached.

I am going to take my HF multi tester to Steve house this afternoon if he is going to be home and put a panel out in the bright sun and test it. I assume it should test 36 volts and a amp figure of whate very I'd on the tag on the back if it's in perfect condition. If I get less than 36 volts and therefore less than the tag says on amps can I still use it? Let's say it reads 30 volts as a example. The mppt would still give me a good charge amps correct?

I wonder if the panels when brand new would test perfect due to sun angle, haze in the air etc?

 

[jimindenver]

Temperature has a big effect on Voc. I have seen a single panel range from 35v normally to over 40v in cold weather. On a day in the 70's you should see around 35v from that size of a panel. I wouldn't take one that was too far under the rated listing in bright light.

The panel will be rated for just over 8a Isc. (short circuit) I can't test anything larger than a 230w here in Denver because it frys my el cheapo 10a meters This may not happen at lower altitudes but you should see what my panels do at 10,000 ft. Woohooo!

 

[jimindenver]

Any more you see a second set of ratings on the panels for what you can realistically expect to see. The main ratings are in a lab under perfect conditions and you will never see that. Even at altitude i have never seen more than 226w out of my 245w panel.

 

[Oneleggedcowboy]

Ok I got a panel!!!! We found one that tested in bright sun at 1.30 pm at 36 volts with my Harbor Freight multmeter. Actually I messed up one multimeter by leaving it in the sun and it quit. Oh well. It tested 7.27 amps. I question this because amps times volts equals warts and this would be more watts than 245. Oh well it works and looks good so I am happy. Now to get me a mppt charge controller. I think I like the Eco Worthy the best, it has a cool meter function. The tracer does not. Now I have to mount this giant thing on the slide in truck camper.

I have a round pipe rack on the back top of the camper. I could put a piece of plywood up there and paint it white and bolt the Z mounts to it. Or I could put 2x4s up there. I figure since this thing is huge it needs more support than just 4 Z mounts. I am afraid it will sag and break the glass or pull the seal loose.

How did you mount yours Jimindenver?

Thanks again Jim!

 

[sushidog]

Open circuit voltage is higher than voltage under a load. Also a brand new panel will probably exceed its rating by 4-5% but will drop to its rated voltage in a couple weeks. Does the Eco Worthy allow you to adjust your charging voltage? If charging a FLA battery, some manufacturers suggest charging at 14.8-15 volts (as does Handy Bob.) Many will only bulk charge at 14.4 volts.

Here's a good read: https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/

Chip

 

[highdesertranger]

if that rack on your camper can handle the panel you could use aluminum angle and bolt that to the rack with u-bolts. that would give the panel full length support. highdesertranger

 

[jimindenver]

Jim hasn't mounted anything yet because he had the bright Idea of starting over from scratch after deciding he didn't like the way his mono panels acted in cloudy weather. So far I have the three 250w poly panels, the stupid expensive controller to run them, 100 ft of 1/0 cable for the various runs, an industrial inverter AND yesterday I picked up three Lifeline 8-D's. I am waiting on lugs to show up and have to pick out switching, fuses, ect.

So I am hoping to get it all mounted this summer. When I do it will be with home made L brackets on the roof. On those will be a frame hinged on one side so that I can lift them up for cleaning and roof maintenance. I don't plan on tilting them while camping, the thought is to have enough to not need to tilt.

 

[Oneleggedcowboy]

I agree with enough to not need to tilt! One legged guys don't like ladders.

Another question is that I can get big 12 volt marine batteries super cheap. They are maintenance free. So can I use those because there is no way to check fluid level. What about equalization every month, can these handle the process?

 

[WheelEstate USA]

Cowboy...this solar has several answers depending on the user's needs. Often cost is a big part of the equation, it is with us. Our battery choice was Wally's deep cycle 122ah for 100 bucks. (have 100 W panel). Generally rule of thumb says 1 W of panel per each ah of battery, so I could actually use a more panel, but our needs are few and the battery is healthy. Will be adding more as money allows.

What do you plan to power?

 

[Oneleggedcowboy]

Hey Bindi people! That's hello in Southern. Well this winter will be my 3rd snowbird trip to Quartzsite and points west!

Bluntly I like Drip Coffee, microvave oatmeal and potaos, TV with my electric signal booster, and lots of lights! The first year I went in my slide in camper with Sadie Mae the killer Pug. Then last year I went in my girlfriends 24 ft camper with 400 watts of solar and 4 trojan batteries with Sadie Mae and we acquired Mic the Hangin Tree Stockdog in Wickenburg Az. This year lovely Susan, the main squeeze is in Chicago nursing her mother. Therefore it's back into the slide in truck camper with Sadie, Mic and this year I am adding a 2 horse trailer and Chips my Paint trailriding horse. Boondocking on Blm and National forest is apparently ok with your horse I hope, does anyone know the rules on this?

So I want all my comforts of home and since I don't use the blow dryer as such like Susan I figure 245 watts and two 13 volt batteries should do it.

Your Wally World battery has a amp hour rating, I can't find amp hour on marine 12 volt batteries, where do you get it?

 

[Oneleggedcowboy]

Oops that's two 12 volt marine batteries.

 

[Optimistic Paranoid]

Another question is that I can get big 12 volt marine batteries super cheap. They are maintenance free. So can I use those because there is no way to check fluid level. What about equalization every month, can these handle the process?

If by "maintenance free" you mean there are no caps you can remove to check the fluid level and add water as needed, then DO NOT try to equalize them.  Equalizing a flooded battery is a deliberate overcharge, and it WILL boil some of the electrolyte out.  You will need to add some distilled water to the cells after each equalization charge.

BTW, it sounds like what you are talking about are neither gel cells nor agm batteries, but rather the old style sealed batteries that cars started using back in the 70s.

Regards
John