Eco-Worthy 12v solar panels, Now drifting to... mono vs poly

That's why there are real life users. Here you can see just about any combination of gear being used in a multitude of ways successfully. We compare the results, cost, convenience, up side and down side of those systems. If you can't find a solution, you can at least get ideas.

Hi jrnymn7,

I'd really recommend a temperature sensor for what ever controller you decide on. They do cost more but the sensor will increase the battery life.

When I purchased my system it was $4.50 per watt. MPPT made financial sense at that price. I also had a #10 prewire and going to higher voltage (33) made lots of sense.

Today, with panel price per watt in free fall, I would probably go for a pwm with temperature compensation.

If the roof real estate has already been maxed out, MPPT may provide for more energy harvest per day.

Thanks, Green. That's my thinking, exactly.

It's like spending an extra $3000 on attic insulation for your house, in order to save $100 a year in energy costs. Likewise, if the break even point surpasses the life expectancy of a given electrical device, it's just not a good investment.

But the need to make a better informed choice comes in when comparing a $100 mppt with say a $30 pwm. That extra $70 could be well spent. Unfortunately, Marketing and Dis-information has us all by the short and curly's.

jr, for maximum value start with a cheap PWM controller and nominal 12V (~18V) panels. Make them somehow portable, even if only to lean against your RV. Run these for a year and then figure out what the ideal system would be, and spend your big money and drill holes for that.

I wish I'd done this, I'd be $1500 richer right now. My Kyocera 315 panels and my FlexMax 80 are nothing but museum pieces, while my Renogy portables and cheap PWM actually get the job done. If I buy enough Renogy panels to bump the voltage, maybe I can get some use out of the Flexmax. But until then I've basically pineconed myself.

Consider:

--"Cost per amp" of panel at 12v PWM. Now SUBTRACT the cost savings of PWM vs MPPT.

--"Amps per square foot" of panel at 12v PWM. These are "actual amps" vs "potential amp gains" of MPPT, subject to heat loss, light clouds, etc etc etc.

Dont spend $500 additional on an MPPT (it really IS MPPT) controller than cannot possibly harvest an extra $500 worth of power over its service life.

Isc goes up with heat, Voc and Pmax go down. What happens at 14.2976v ????

BFL13 wrote:

RJsfishin wrote:
Yeah, all you little straps, quit tryin to be big straps when you don't understand it all !

Heres a hint, 12v panels are for RVs and boats. 24v panels are made for houses,.....take it !

My 12v 300w system w/ a $8 controller works great. If I ever need another panel or 2, I would maybe series them up and go MPPT, but it sure isn't on my wish list.
BTW, I have a brand new 20 amp MPPT still in the box, not to speak of several PWMs, so if you think MPPT is so great, send me a $50 bill, and its yours. But tell ya right now, I only paid 12 bucks for it :)

That would be this RJ Special which I bought last year at his urging. :) It turned out to be a fake MPPT and is actually an ordinary PWM, but it does well at that job.

I used it for a while with my 130w panel. Its charging profile is to get to 14.5v and stay there till dark. The lights on it tell you what the state of play is--more lights means the battery is getting higher in SOC.

I sold this along with my 130w panel and the guy used it no problems all summer.

So actually this is a decent little controller as long as you know it is not MPPT and don't try to run a 24v panel with it :)

http://www.ebay.ca/itm/20A-MPPT-Solar-Panel-Battery-Regulator-Charge-Controller-12V-24V-Auto-Switch-KJ-/171112316078?pt=LH_DefaultDomain_0&hash=item27d716bcae

OK I confess. I did try this with my 230w panel on the notion that it would just treat it as any other 8.3a panel and that would be my max amps, same as my 130w panel doing its 8.2a. ( I didn't know about bucking etc then)

Result was the little controller lit up all its lights which started flashing rapidly like some kind of crazy UFO. I disconnected. I figured that's it, I fried it. Tried it back on the 130w panel and it worked normally! Whew, I got away with it.

Thanks guys... very helpful.

Jim, I'm leaning toward poly, only because there seems be an issue with cloud cover and mono's, whereas, I doubt shade from a tree limb or something will be a continual issue. I'm also leaning toward mppt (if it will work well with 12v) because during the 10-14 hours of hot summer sun, with little to no cloud cover, getting every little watt out of the controller is not as important as maximizing power scavenging during the short 3-5 hours of often cloud covered sun during the fall and spring.

Regarding heat: it is my understanding that solar panels loose significant amounts of efficiency once they get to a certain temperature. I haven't seen anyone addressing this issue. ( perhaps in past threads they have? ).

Who cares what panels are used? A system that covers someones needs, within their budget and conditions is a good system. It may not work for me for a number of reasons and I don't get upset if what I use or do isn't for someone else.

Tomorrow there may be a new panel, controller or battery that will change all of our minds, who knows.

RJsfishin wrote:
Yeah, all you little straps, quit tryin to be big straps when you don't understand it all !

Heres a hint, 12v panels are for RVs and boats. 24v panels are made for houses,.....take it !

My 12v 300w system w/ a $8 controller works great. If I ever need another panel or 2, I would maybe series them up and go MPPT, but it sure isn't on my wish list.
BTW, I have a brand new 20 amp MPPT still in the box, not to speak of several PWMs, so if you think MPPT is so great, send me a $50 bill, and its yours. But tell ya right now, I only paid 12 bucks for it :)

That would be this RJ Special which I bought last year at his urging. :) It turned out to be a fake MPPT and is actually an ordinary PWM, but it does well at that job.

I used it for a while with my 130w panel. Its charging profile is to get to 14.5v and stay there till dark. The lights on it tell you what the state of play is--more lights means the battery is getting higher in SOC.

I sold this along with my 130w panel and the guy used it no problems all summer.

So actually this is a decent little controller as long as you know it is not MPPT and don't try to run a 24v panel with it :)

http://www.ebay.ca/itm/20A-MPPT-Solar-Panel-Battery-Regulator-Charge-Controller-12V-24V-Auto-Switch-KJ-/171112316078?pt=LH_DefaultDomain_0&hash=item27d716bcae

AND it isn't MPPT. ;)