100W Poly panel in Home Depot

The lifespan of your house batteries... for one. Any one voltage no user control device is a battery lifespan killer.

Almot wrote:

Gonzo42 wrote:
That might just make me go for it. Wonder how much the controller and other required items cost?

With 100W you need 8-10A PWM controller. The cheapest 3-stage controller with temp compensation will cost $40-50: Sunsaver SS-10. Few more bucks with free S/H on Amazon. You could find a whole bunch of fly by night gizmos for $15-20 on Ebay and Amazon, but I strongly recommend against this.

Wires with connectors - $15 or 20, depends on the length.

100W panel is a substantial source of power but not unlimited. It would run DC circuit of propane fridge, lights, pumps, cell phone. Or will top the battery up after 1 hour on generator. Living off 100W solar alone for several weeks would be difficult unless you are really in minimalist mindset.

Almot - I bought the home depot panel, and now I'm shopping for a controller. In the one you are recommending, what makes it stand out? What is the difference between it, for instance, and the "fly by night gizmos for $15-20?"

Thanks,
-Speak

Searching_Ut wrote:

With the several series parallel type mppt setups I've looked at they all had output current drops more significant on the non shaded string than you would expect if you shaded out one leg.

I meant 24V panels all parallel with MPPT. Lower current, less resistance losses than with 12V, lower cost per panel wattage, higher cost for MPPT. The result is more output amps, though hot weather would TAD negate this.

Top-end MPPT have better algorithm, more programmability than PWM, and higher amps.

Bogart PWM is the only exception, it's hooked up to "brains" of the Tri. The Tri will control the controller, so to speak, adjusting it on the go, and clipping excessive amps up to 45A input, so you can use more panel wattage in shoulder sun. But peak amps are still 30.

Almot wrote:
Yes, parallel wiring is (usually) more reliable in partial shading. Though this is a panel bypass issue, not a PWM-MPPT issue. Parallel would work with MPPT same well, if not better. Depends on location and weather pattern.

With the several series parallel type mppt setups I've looked at they all had output current drops more significant on the non shaded string than you would expect if you shaded out one leg. For instance, on a 4 panel setup, two strings of two panels if you shaded out a single panel on one leg the output drop was more like two thirds loss rather than the 50 percent or less you would expect. With single panels in parallel and mppt controller I've always seen similar loss. They seem much to require balanced panels more than the simpler PWM setups do. Some controllers may do better under these sorts of conditions based on how they are programed, but based on the ones I've observed, simpler can be better in many situations.

Bogart controller with Trimetric monitor is a nice combo, but you have to buy exactly a combo - both controller and Tri. Without Tri, this controller won't work well. Many already have a Tri, though many have a different monitor or no monitor and no plans to buy one.

Yes, parallel wiring is (usually) more reliable in partial shading. Though this is a panel bypass issue, not a PWM-MPPT issue. Parallel would work with MPPT same well, if not better. Depends on location and weather pattern.

Almot wrote:

Arrays larger than 400W are usually made of bigger high-voltage panels. Cheaper per watt, more expensive controller, and easier install without rooftop junction box. Though they never ship big panels for free, you have to be near some solar warehouse.

I wasn't all that concerned with price per watt as much as I simply wanted a system that would perform in the conditions I wanted. Being the guy always asked to troubleshoot and sort out generator/solar issues for others, I very much prefer the flexibility of a parallel setup and PWM controller which doesn't get "confused" as easily. That little bogart SC controller has better adjustability and controllability that anything else I've seen available right now and doesn't really care if some of the panels are not producing as well as the others because of shading, tilt or what have you. Obviously if I was setting up the system on a fixed facility roof, or a tracking system my choices would be different.

If your Class C has rubber-ish EPDM roof with 3/4 plywood, you'll be following in footsteps of many before you. Dicor sealant under the bracket foot, few tapping screws #10, - done. There are dozens screws there already.

200W you'll find for less $ per watt than this 100W panel. Probably for $160-180. The problem with 200W panel is that it is nominal 24V and therefore needs MPPT controller, those are more expensive.

Using 200W as a portable? It weighs 40-42 lbs and monstrous size doesn't make it any easier. Unless you camp in one place for weeks at a time. I have 2 of them - on the roof, this is where they belong.

With your mostly hookup camps, and some charging from alternator, you could do without 200W on the roof. Probably - without any solar at all. Trick-L-start will take care of both chassis and coach battery.

Gonzo42 wrote:

My purpose is to mainly maintain battery charges both house and chssis. We primarily use FHU sites (I say primarily).

I now have a 200W PSW inverter mosttly for the Sat TV receiver and the new TV I am currently installing.

I habitually use a small battery charger off 120 VAC to keep the chassis battery up, since shore power alone won't do that job but only charges house batteries.

May I suggest installing a Trik-L-Start or similar device (though most of the others are considerably more costly) to keep the chassis battery up? It seems to me it would be a lot handier and more efficient with solar than rigging up an inverter with a battery charger.

Should I stall until a reasonably priced 200W panel is available?

I'd say don't stall. The size of the module is dependent on the number of cells. You wouldn't want to schlep around a 200+ W panel. The price of these Grape solar panels is low since there is no shipping involved. I'd suggest to buy two to achieve a 200 W array. A piano hinge or two small butt hinges attached to the frame sides will result in a "suitcase" although it might be easier to deploy them as singles.

As far as roof mounting, there should be no worries about fasteners through the roof membrane. That process has been covered extensively on this Forum. I have not heard of one leak through a panel bracket. For the very squeamish, there is also VHB tape but that is not a good attachment for a membrane roof. It does work brilliantly for fiberglass and aluminum roofs, though.

As a former department scrounge, a long-term tech and an engineer, I think I can build whatever is required.

Having said that, a 24-foot Class C as limited roof space. Couple that with a reluctance to drill into the roof and I have a personal problem.

My purpose is to mainly maintain battery charges both house and chssis. We primarily use FHU sites (I say primarily).

I now have a 200W PSW inverter mosttly for the Sat TV receiver and the new TV I am currently installing.

I habitually use a small battery charger off 120 VAC to keep the chassis battery up, since shore power alone won't do that job but only charges house batteries.

Should I stall until a reasonably priced 200W panel is available?