Renogy solar?

BFL13 wrote:

RJsfishin wrote:
BLF, thanks for your comments.
I have all the specs on the panels, even tho they don't mean much to me.
But I remembered the IMP specs at 5,12a on the 90 watt, and 5.35a on the 100 watt. Add them together for a total of 10.47. Seldom if ever do I buy anything that isn't exaagerated a bunch, so seeing 10.4 output, I was delighted. And that was w/ 2 near full charged batteries, w/ only a bunch of lites on to get the 10 amp output. Not long after turning everything off, the controller would start into float mode w/ only a couple amps output.

ISC 6,15 & 5.72
VMP 17.56 & 18.7
VOC 21.96 & 22.20

You should get Isc. First find what Isc really is by measuring at the panels with no battery connected, then connect and see what amps you are getting on a low battery.

If panel Isc is less than spec:

-could be some haze
-panel not tipped high enough
-sun not high enough
-temperature doesn't bother Isc so unlikely a factor unless extreme

If panel amps not reaching battery,

-confirm battery voltage is under 13.x
- check wiring

(Your Isc amps will decline slightly once batts get up to 13.x as seen on your panel's IV curve. eg, might see only 7.9 instead of 8.2)

When checking Isc at the panel, aimed at the sun when sun is high, tilt the panel up and down slowly to find max amps.

With 12v and PWM, only the Isc spec means anything. Vmp, Imp mean nothing (those are for the MPPT crowd) Voc means nothing either, since it changes a lot with temperature and when it does , nothing happens with your amps, you still get Isc when Voc is down a whole volt. Ignore all except Isc.

My swivel is at fixed tilt and tilt is a bit low, so I get Isc mid day ok, but when sun is lower earlier and later I get less than Isc with panels pointed at sun. I could get Isc then if I tilted higher for the lower sun. Eventually when the sun is even lower than that early morning/evening, you can't get Isc even when tilted right up because the sun is in atmospherics that low.

I chose the lower fixed tilt for when I just leave it pointing South all day. In that case, you want it lower than perfect for noon so you can get more in the shoulder hours, so there is an optimum fixed tilt for that. There is a formula for figuring that out for each season and latitude at www.macslab.com

What do you think of the idea of splitting the angle of the different panels? Maybe aiming the bigger one optimized for getting out of bulk as early in the day as possible, and the other for keeping the amps and volts above the charging threshold as late in the day as possible? So one panel probably biased more east and the other more west?

Hmm I guess that is more optimized around battery charging though, and does not take into account whether or not you are getting enough yield during the day with real time usage loads. You are generally much better off with any load you can draw from the array directly. You skip all the losses of discharging and recharging the bank like Peukert losses and charging efficiency losses entirely.

Jim

W/o getting real technical (I don't like real technical) it seems to me like it would be a wash. But being as I'm set up to move the polar mount every hour (if I'm around) or 2 or 3, I don't see it helping any.

RJsfishin wrote:
W/o getting real technical (I don't like real technical) it seems to me like it would be a wash. But being as I'm set up to move the polar mount every hour (if I'm around) or 2 or 3, I don't see it helping any.

No if you move throughout the day you get the max benefit. Peak power plus long charging day.

Jim

RJsfishin wrote:
being as I'm set up to move the polar mount every hour (if I'm around) or 2 or 3, I don't see it helping any.

Rotating it helps less (compared to fixed tilt), than fixed tilt compared to flat. Fixed tilt improves the output by 60% in winter, and 20-30% in summer, depending where you are. You may gain another 10%-15% by rotating it every few hours, but normally it's not worth it.

Also, don't listen to BFL when he says that solar is "all or nothing" and generator is inevitable :). With 120W this is correct because such a panel is a little more than nothing, so to speak. Increasing the wattage 4-5 times with some increase in battery bank is necessary to collect enough on cloudy days to stay put for 3-4 days, until weather improves. "Adjusting" yourself, i.e. your consumption might still be necessary from time to time. In coastal BC there can be more than 4 days of clouds, so ultimately an all-solar RV is difficult thing to accomplish. RV is not a home, and even in a solar home you have to adjust your consumption - which doesn't necessarily means sacrificing something, but replacing some devices, and keep an eye on it, to be able not to use generator. It's not that people "can't", it's that they don't want.

In May at 49N, with my 130w in the contraption, ran a controlled test in perfect conditions each time (so results are valid), got daily:

Flat- 56AH
Tilted-70AH
Tracking (three moves a day)-90AH

In terms of percentage improvement
-70-56 = 14/56 = 25%
-90-70 = 20/70 = 28%
-90-56 = 34/56 = 61%

Such a test requires a load running all day to soak up the AH. With just battery charging, the afternoon amps drop off so you don't get the "full" AH you could have had.

So best time to do some extra things where timing is optional, is in the afternoon when you can run them "for free" without affecting battery SOC much if any.

This year with my 200w in the swivel contraption and the 130w just tilted South, I can get the same 70AH from the 130w and 200/130 x 90 = 138AH for total of 208AH. A lot of that goes to waste on perfect days with our daily usage being more like 80AH days.

However, most days are with mixed sun/cloud. We can keep up by aiming the 200w at the sun whenever it appears. If it clags right in, we are back to gen/charger in a three or four days. 458AH bank to 50% is 229AH and 229/80 = 2.86 days. So on the fourth day we are a tad below 50% and out comes the gen and the 100amp smart charger. (takes about 2 hrs of gen time to do a 45-85 )

Just after they told me I wouldn't need my generator ever again !!
1.5 amps max !:?

Solar homes people say "go big - or go home". You can't go big with RV - there is no space. If you want to keep the same lifestyle in RV as in your shore home - then generator is your destiny. Even if max up your solar wattage and battery bank size.

BFL, how often did you have to rotate your tripod to achieve 28% boost compared to fixed tilt?

H Almot,

At the same time RV's are far less energy hungry than a home.

An RV could, with some effort have two layers of panels. One on top of another. While traveling the would not be deployed, but once the RV arrived it would be easy enough to have them "push out"

Almot wrote:
Solar homes people say "go big - or go home". You can't go big with RV - there is no space. If you want to keep the same lifestyle in RV as in your shore home - then generator is your destiny. Even if max up your solar wattage and battery bank size.

BFL, how often did you have to rotate your tripod to achieve 28% boost compared to fixed tilt?

As stated, three times a day. RJ has found that is sufficient too. At sunset to SE, 1145 to S, 1445 to SW (where 1315 is high noon)

The dips in amps between moves are small so you don't lose much in AH. Just not worth it to be rotating it more often.

If one of those spotty days for when the sun is out, then you might play with it more to grab the sun when it is available--if you have nothing better to do with your time! :)

I can see the attraction of having a roof-full of flat panels and then forget about it for the next several years. You get what you get and there is nothing you can do, so just enjoy your day. :)

I can see the attraction of having a roof-full of flat panels and then forget about it for the next several years. You get what you get and there is nothing you can do, so just enjoy your day.

My kind PV array installation - Leaves more time for fishing