Price of Solar! WOW

JiminDenver wrote:
You might try calling some solar installers in your area and seeing if they have any left overs. Many order a extra panel or two per project but don't want to go thru the hassle of selling them.

Problem with that is the ones used for buildings are much larger than the available space on most RV's. The Kyocera 140 Watt is probably the best selling RV panel and what makes it attractive is its narrow width. It can fit in spaces and not be shaded by something else on the roof of the RV.

CA Traveler wrote:
...
PWM allows (or did allow) the use of a lower overall cost but the Eco Worthy controller seems to be closing the gap)

So I waited before taking the plunge and hopefully it's "Do it right the first time". Which of course is unlikely to happen.

Not likely to happen unless you do it fast. When Don told me 2 years ago about Rogue 30 being the best MPPT for a "small" system, I couldn't quite wrap my mind around 500W called "small". But he was right on both points, and 500W today IS small. I haven't finished yet all the details, but already thinking of expanding, with more loads in mind.

When I read that post by BFL again - thanks God the (tedious) discussion of PWM vs MPPT didn't pick up this time - he didn't mean to compare anything. You asked whether 40-45A is reasonable to expect with 750W array, and BFL provided the answer based on 130W panel.

As to Ecoworthy "closing the gap", it can only handle one 24V panel, and yet costs several times more than some "ebay special" PWM. This can be compared to closing the "gap" between two sides of river with a rope. You can grab the rope and get to the other side but without your horses and cargo. A proper bridge is better, but then again it takes time and money to build. Ops - looks like I am starting discussion now. Didn't mean to. Read up more, CA. There is no universal recipe for everybody.

Almot wrote:
Here goes this of worms again, PWM vs MPPT, on 10+ pages :)... No, thanks, I'm out.

Funny. PWM and you don't have to worry :)

Lots of options to consider in setting up the system. Breaking each down and and working out the possibilities is the fun part for me. Actually getting it set up, crossing your fingers and seeing it do what you designed it to makes the effort worth while.

It is interesting seeing how each sees their needs and how they fill them.

Great input - Thanks to all.

Hi CATraveller,

I do series parallel for an input voltage of 33 to a Blue Sky 3024di controller. It works well.

Here goes this of worms again, PWM vs MPPT, on 10+ pages :)... No, thanks, I'm out.

I've never been comfortable comparing PWM and MPPT. Use 24V panels on PWM? - nope. Use 2 12V panels in parallel on MPPT? - nope. Us 2 12V panels in series on MPPT? - questionalble.

An 18V 12V panel loses the power of 18-14.8=3.2V * the Imp. While MPPT has to convert the higher voltage to a lower voltage and from the MS manual the larger the panel vs battery differential (12V batteries being the worst) the more the controller losses.

PWM has to use (from a practical standpoint) a combiner box and larger wire to the controller, as in higher cost. While serial MPPT panels have less wiring cost.

Panel mounting costs? MPPT panels are heavier while PWM would use more and lighter panels for equivalent wattage.

Roof space? And here is the big biased item on these boards. PWM allows the use of smaller panels to work around AC's so mount them 1" above the roof. I've talked to and taken pictures of several people that have raised panels. One in Deep Creek Alaska of all places! My larger heavier MPPT panels will be mounted 6" above the roof and I estimate I'll have summer time shadows on the panels before 6AM and after 6PM regardless of rig orientation.

PWM allows (or did allow) the use of a lower overall cost but the Eco Worthy controller seems to be closing the gap)

So I waited before taking the plunge and hopefully it's "Do it right the first time". Which of course is unlikely to happen. I can only speculate what I'll learn vs reading about what other posters have learned.

Let the fun begin!

CA Traveler wrote:
I estimated 40-45A for 750W flat mounted. Seem reasonable? That should/better handle my needs.

So as a possibility for anyone it appears that the MS MPPT could handle a 4th panel with minimum derating.

1) 40-45A - in terms of Morningstar this would be TS 45 model - will still clip some amps at peak sun, but not much. Strictly as math goes, 45A controller for 750W is the same as 60A for 1000W, but the system efficiency of the former scenario will be higher because Vmp is lower (i.e. you lose more % of daily harvest). I would say - go for it.

2) Hopefully you know your needs. For some people (and/or some locations) 45A system is not enough.

3) What MS MPPT and what 4th panel? :)
Yes, TS 60 could handle 4*240W. Yes, there will be some clipping. Depends where and when you camp.

Also - depends on your consumption pattern. I rarely give my 490W array with Rogue 30 (also slightly underrated controller for this array) to work full power, because rarely take more than 30 AH from my bank. Such an oversized system for my needs was build on purpose because on a dark day 30 AH is exactly what it would harvest, and then I'm golden. Or, I can use 60 AH on a dark day if I need to, ex. running a vacuum or power tools, and get battery to 100% the next day if there is any sun at all. If you, like Jim, are trying to avoid noise and smell, the system should be oversized (doesn't mean getting an array way too oversized for a given controller - this of course would be meaningless). There is no such thing as too much solar - don't remember who said it, but this is true.

CA Traveler wrote:
I estimated 40-45A for 750W flat mounted. Seem reasonable? That should/better handle my needs.

So as a possibility for anyone it appears that the MS MPPT could handle a 4th panel with minimum derating.

My 130w flat at 49.3N in May got 7.2a at high noon with PWM. 750/130 x 7.2 is 41.5 so reasonable indeed. Farther south with the sun higher at noon it could be a bit more like 45a. MPPT could do better but then loses that in the heat of the sun, so call it even with the PWM figure.