I would LOVE to get 10-12 amperes of 12 volt grade charging for my new group 31 Lifeline.But I have a motor-scooter size toad, that forces me to the roll-up kind of solar panel, and woe is me, these panels demand an MPPT charge controller. Champagne taste, and beer budget.I hate the thought of using a 2-cycle generator and charger during Armageddon grade storm outages (clouds depart - sun comes out - power stays off). Wheeling that monster 31 up & back on the Trail Of Tears to the gen shed bums me out. So does the thought of hiring a back hoe to lay a subterranean line 150' to the house. The three freezers are in the gen shed.But MPPT is so expensive. Jesus and I figured out which trees have to be felled in order to get sunlight to the panel.Any suggestions for (hah!) least expensive MPPT controllers?

AFAIK the least expensive "true MPPT" is the 20a Eco-Worthy MPPT for $102.It has only a 42Voc limit so it can't take two 12v panels in series but it can do them in parallelhttp://www.eco-worthy.com/catalog/mppt-solar-charge-controller-free-shipping-p-182.htmlThere are many cheaper "MPPT" marked controllers that are actually just PWM so beware of those "fake MPPT" ones.

The 68w rolls can be run with a PWM.

Aghh, My dumb, Jim: I have no idea of the link for 68 watt roll panels. Can you enlighten me?

Mex,I've seen reports by those who used these unisolar 68 watt and 132 watt 'roll up panels, as portable panels that were rolled and unrolled often, that they began to break down rather quickly when rolled and unrolled often.Also the sides of the panels are still sticky Butyl and stick to and make a mess on anything they touchUnisolar said they should not be rolled under such and such a diameter, and I found mine shipped to me about 4 inches under that diameter. I think it was 22 inches but dont quote me.I really think trying to implement these as a portable solution is not wise. People seem to think they are indestructible, but there are lumps where the diodes reside and I imagine enough pressure on one of those could break it.I think I'd be getting 2 framed panels and attaching locking handles to one side and a piano hinge on another if I were to go portable.I have the 68 watt unisolar pvl68 with the mc3 connectors, and it does seem to do well in lower light, but it sure takes up a lot of space to make those 68 watts, and was not a simple peel and stick in my application. Going over the crown in my roof caused a couple kinks here and there and these kinks are now getting ugly and I fear for its ultimate lifespan.It will be 3 years installed, in february '15.

Call this shop and ask to speak to Jack about his flex panels and MPPT chargers: http://store.evtv.me/products.php?cat=22

Roll Up Solar Panels / Ogre MPPT Controller | Good Sam Community

pnichols
Explorer II
Nov 27, 2014
pianotuna wrote:
Hi Phil,

I'd love to know more about the solar magic system and the technology they use.

Don,

This document from TI provides a pretty good explanation of how the SolarMagic module improves the harvest from solar panels:

http://www.ti.com/lit/an/snosb67b/snosb67b.pdf
JiminDenver
Explorer II
Nov 25, 2014
BFL13 wrote:
Once JiminDenver nails some panels to his roof he will need a new hobby! Buying and selling solar stuff every few months only works well if you have portables. :)

Now listen, I'm already having a hard enough time mounting the gear and losing the early and late power. I'll probably keep a portable just to take advantage of those times. Plus the systems are getting a good enough response that if I find more cheap panels, I'll just make some more and sell those too. :)
pianotuna
Nomad III
Nov 25, 2014
Hi,

Here is a great article on panel efficiency and what to choose: Which solar panels are most efficient
BFL13
Explorer II
Nov 25, 2014
Once JiminDenver nails some panels to his roof he will need a new hobby! Buying and selling solar stuff every few months only works well if you have portables. :)
JiminDenver
Explorer II
Nov 25, 2014
BTW Poly panels and mono panels do not mix well as the Voc never matches up. All of my mono's get higher voltage in bright light and considerably lower when the clouds roll in daily.

I haven't been impressed with the responses from the seller of the 300w panels. The specs don't show well on the ad and no brand is given, just that they are made with Trina components. He avoided the questions in his response so I have switch my attention to 280w polys for $212. Still too big for the Eco-w but I didn't intend to use them after mounting.
pianotuna
Nomad III
Nov 25, 2014
Hi Phil,

There are some panels that have more than one layer of material that output 27% of the energy hitting them vs the 17 to 20% that "regular" panels do. Unfortunately they won't be under $1 per watt.

Do you have any further knowledge of the "solar magic" and how it works?

On a long run I'd go for the maximum voltage that the MPPT would accept. However that does mean that efficiency at the controller drops.

Some panels have diodes between each and every cell. Those do the best output in shade conditions, but of course avoiding shade is always better.

pnichols wrote:
Hmmmm ... if one was to have an even numbered quantity of solar panels, how about compromising for best average performance by making half of them mono and half of them poly?

Now for the tough question: Assuming you want to spend the money for a high enough input voltage spec'd MPPT - what would be best for a couple of portable panels that could wind up being up to 50 feet from the batteries -> put the two panels in parallel or put the two panels in series?
(Also, I believe that the SolarMagic technology I mentioned earlier helps reduce the effects of partial shading.)
JiminDenver
Explorer II
Nov 25, 2014
I had my panels on 50 ft cables so that they could be kept out of the shadows.
BFL13
Explorer II
Nov 25, 2014
pnichols wrote:
Hmmmm ... if one was to have an even numbered quantity of solar panels, how about compromising for best average performance by making half of them mono and half of them poly?

Now for the tough question: Assuming you want to spend the money for a high enough input voltage spec'd MPPT - what would be best for a couple of portable panels that could wind up being up to 50 feet from the batteries -> put the two panels in parallel or put the two panels in series?

Series gives you less voltage drop on 50 foot wires going back to the MPPT controller in the motorhome, but doesn't parallel have some advantage ... I remember reading about parallel panels (I think) having less output reduction with partial shading? (Also, I believe that the SolarMagic technology I mentioned earlier helps reduce the effects of partial shading.)

Phil dig out and read all 9 or however many it was of these posts which will answer most of the questions you are asking. EG

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27304664

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27304651

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27304694
dewey02
Explorer II
Nov 25, 2014
Deleted
JiminDenver
Explorer II
Nov 25, 2014
Snowman9000 wrote:
pianotuna wrote:
Hi Mex,

Sunelec still has the 136 watt Uni-solar flexible panels.

$76 for 136 watts

I believe Solar Blvd has them for $79 right now, if that works better for anyone.

They will have them for that price Black Friday.

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