Still Don't Get It (Solar)

[Grodyman]

What will charge 2 6v golf cart batteries better, a single 270 watt high voltage panel with mppt or two 135 watt 12v panels (parallel) with PWM and why???? Thanks.

Gman

[jrnymn7]

BFL, is that a Fawlty Towers reference?

[JiminDenver]

Again, altitude has it's advantages. You might see a hawk soaring around but at 10.000 ft most smaller birds stay on the ground. The bugs sure do like the heat though.

[BFL13]

pianotuna wrote:
Hi jrnymn7,

Losses when the panel is at 50 C are about 12%. Raising the panels so that air can flow beneath them easily makes sense because it is a passive fix.

This is my 230w panel where it gets to 44C when ambient is 16C and to 51C when ambient is 25C. Hate to think what panel temp would be if flat on a roof like most installations



BTW photo taken in morning with panel facing Easterly. When twirled to Southerly I lower the tilt, then raise it again for Westerly mid-afternoon. My contraption has some tilt angle options for that reason. The wire across the top is to keep robins off. They poop down the panel.

I laugh at those guys who post they don't have to climb on their roofs once they install the solar. They must not have seagulls bombing them, or else they just don't know what is happening. You don't see any graphs of panel loss vs seagull activity in those insolation guides. Might be bad for the solar business. "Basil, don't mention the seagulls!"

[pianotuna]

Hi jrnymn7,

Losses when the panel is at 50 C are about 12%. Raising the panels so that air can flow beneath them easily makes sense because it is a passive fix.

[jrnymn7]

I wonder what a thin line, compact cooling design would entail? I'm thinking along the lines of any power supply, but on a larger scale. A shallow sheet metal box mounted to the back of the panel, making it say 3" deep overall. A fan at either end, tunneling air thru a narrow channel. Or even slots on the ends, and a central exhaust fan blowing out the back?

Would there be any significant net gain?

I guess I'll have to experiment with that, next summer.

[Snowman9000]

Yeah, you can't beat portable panels when it comes to output. If a person isn't running any big inverter loads and has energy efficient stuff, I would think 100-200W of portable could handle most situations. I've posted before how I got 56AH from 100W on a sunny March day in AZ. Sunny, that's the key, though. 🙂

I tested my WFCO 55 in absolute best case wiring conditions, and it only puts out amps in the teens, at 13.6v, during the first couple of hours. So OP's numbers sound right. Poor, but right.

[NinerBikes]

jrnymn7 wrote:
Niner, I pulled the trigger on a wave 3. It's compact size and 1600-3000btu output should do just fine for my little camper.

I'm planning on having a mixture of heating sources; catalytic, hydronic, and a little bit of electric. With 280w of solar, I hope to keep gen charging to a minimum. That little portable set-up of yours puts out quite a bit of power. I'm curious how my numbers will compare to yours, as I am a little ways north/east of Arizona.

Portable panels, aimed 3 to 4x a day, will pull their full rated amps or close, a lot longer than roof mounted panels. Also, because they are in storage when not in use camping, they won't have yearly loss of amps output like solar panels exposed full time to the sun 365 a year.

[MrWizard]

as I am a little ways north/east of Arizona

boy thats an understatement

[jrnymn7]

Niner, I pulled the trigger on a wave 3. It's compact size and 1600-3000btu output should do just fine for my little camper.

I'm planning on having a mixture of heating sources; catalytic, hydronic, and a little bit of electric. With 280w of solar, I hope to keep gen charging to a minimum. That little portable set-up of yours puts out quite a bit of power. I'm curious how my numbers will compare to yours, as I am a little ways north/east of Arizona.

[jrnymn7]

Gman,

You may be surprised how much even a small load on a fairly discharged pair of 6's can pull down the voltage. Nevertheless, 2 hours of "charging" did not replace your evening and overnight usage. This speaks volumes to some, but seems perfectly normal to others.

The good news is, solar will help significantly. The bad news is, your wfco isn't charging your batteries like it should. A 55a charger, on a 208Ah bank is actually a rather high charge rate of C/3.8. You should be able to do a 50-80% (62Ah replaced) in 2 hours, no problem, and in the example you give, a 66-90%, no problem. So, if you were at 12.4v (~66%), and then charged for 2 hours, you should have been up around (and quite possibly above) 90%. So, to go from 90+% down to ~60% (12.3ish) throughout the evening and over night, that would require over 60Ah usage.

I'm not doubting your estimated usage, but I am doubting your wfco's ability to charge your bank in a reasonable manner. Let's say you used 40Ah's throughout the evening and over night, if the wfco had done its job properly, that should have brought you down from 90% to above 70%, (40Ah = 19% usage), not down to 60%. In this example then, that means the wfco only replaced about 25Ah's in 2 hours. How does a 55a charger replace only 25Ah's in 2 hours on a fairly deeply discharged 208Ah bank?

For comparison, I have done a 50-90%, on a larger bank (215Ah) with a smaller charger (45a) in just over 2 hours.

[NinerBikes]

Grodyman wrote:
Thanks all, I'm considering portable. I use most power during winter when running furnace all night. I roughly figure I use about 40-45ah a 24 hr cycle based on my multi-meter readings in my 208ah bank. I read 12.4 first morning (running furnace overnight and watching 2 hr movie that evening off inverter), and after charging with WFCO onboard for two hours on the Honda 2000, ran heater all night and watched a movie again, and read about 12.3 the second morning. My Rockwood Minilite likes the heat it seems. In summer, without the furnace, I figure about half that consumption rate.

I'm thinking a 12 solar panel, maybe 80 watts, or two 60's, and using one of the Morningstar junctioin box mounted controllers.....

Gman

There's your problem! Buy an Olympic Wave 6 catalytic propane heater, some hose, crack a top vent and a window, and turn that blower fan off. Saves electricity, saves gas from your generator too. Your heater fan sucks 5 amps while running at least. I know mine does, and it's annoyingly noisy to boot, at night. The Wave 6 takes no electricity, it does take a little bit of venting, and is far more efficient 96%, with use of propane. Your heater blows 40% of it's heat energy outside out the vent, as exhaust.

TT is a Palomino Gazelle G210.

Before I got the Wave 6 my usage was identical to yours. I bought a 120W portable solar panel. It's for sale, very lightly used. PM if interested. I'm in so cal.



This was first week of Jan 2014, right after the Las Vegas CES convention. I harvested 30- 35 amps that day. By Feb, you will see 40 +, by June 60 amps / day, with aiming 3 or 4x a day following the sun.

I was in Montana and harvested 55 amps on the 3rd day, June 16th, camped on the Madison River, after 2 days of camping without charging and about 75 -80 amps down on my battery. By noon, on the 4th day, I was fully charged again, with this 120W portable solar panel unit. Plug and play.

[NinerBikes]

Edit

[Grodyman]

jrnymn7 wrote:
Gman,

First off, the numbers don't line up. 12.4Vbatt is about 66% soc. 45Ah usage would only be 22% of C. 100-22=78%. So, either the batts were not even near fully charged to begin with, or the Vbatt reading was with a load on them, and thus lower as a result of peukert effect.

If you can provide the size of wfco you have, we can estimate how many Ah's are being replaced in two hours, from 12.4v/66%soc. Clearly, it's not enough.

You're looking to go portable? In that case I recommend you save considerably on pwm over mppt, and put the money where it counts... proper wiring. Do NOT buy a kit that offers 10ga, or less. And yes, 24v panels are usually much cheaper, but there are deals to be had with 12v. I just paid $1.05 can./watt for 140w 12v panels. And I bought a 30a pwm for $35can. Subtract 15% off those prices for $$u.s.

Moreover, mppt only makes a significant difference on large solar systems. I've crunched the numbers, and an average daily increase of say 15%, using mppt only translates to about 20Ah on a really good day, and much less on a short or cloudy day. And going portable blows those numbers out of the water.

The nice thing about going with two panels vs. one is you can always use only one, if two are getting the bank charged up too quickly. Your needs will likely change with the weather, so it's nice to have options.

I figure I used roughly 90ah over two days/nights all included, with a two hour charge in between, and my batteries ended at 12.33ish (only draw being fridge on propane and co monitor etc. when measuring). Seems fairly accurate.....I roughly figure the 2 hour charge (WFCO 8955) replaced about 38ah.....ending with 75% capacity.

A Trimetric is in the future.

Gman

[jrnymn7]

I wish it was spring. I wanna get going on putting to use all the info you guys have supplied me with!

The solar install will definitely be an interesting project, as I figure out a somewhat universal mounting system for the various situations I find myself in. That smoke you smell will either be a bad connection, or my brain going into overload!