How Much Solar ? First Hand Report

[RJsfishin]

Just got set up here in Quartzsite, two 100 watt solar panels on my receiver hitch mounted polar mount, moving it 3 times during the day.
Panes were partly shaded by an old power pole till 9 am, then full sun all day. Solar display was blinking by 2pm, batts near full charge. We are a little conservative w/ led lites etc, but still burn sat tv at least 6 hrs a day.
This 200 watts (190 actually) it more than enuff for us, ......if we can depend on the sun even 50% of the time.
All this hype about voltage drop,......undersize wiring, etc etc, is a serious waste of time IMO,
......my voltmeters looked better when I got up this morning, than they have ever looked running my generator. I am thrilled w/ solar here in AZ. I wish I could be 1/2 this thrilled in Oregon ! :))

[RJsfishin]

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27422525.cfm

[RJsfishin]

[NinerBikes]

That's a mighty compact package for 190 watts. Take a pic of the back of the pole mount and bracket fabrication, por favor.

[RJsfishin]

Darn pole ! A bit later the pole goes thru both panels, killing them both for about 20 minutes. But, when ya have too much solar, we don't haggle about a lil ole pole getting in the way ! 🙂

[BFL13]

RJsfishin
Posted: 02/26/13 04:24am Link | Quote | Print | Notify Moderator

Specs on the panel I have coming,...
.
Maximum Power(Pmax):90W
Tolerance:±3%
Maximum Power Voltage(Vmp):17.27V
Maximum Power Current (Imp):5.2212A
Open Circuit Voltage (Voc):21.934V
Short Circuit Current (Isc):5.638A
Maximum System Voltage:1000VDC
Number of cells:72Pcs
Solar Cell Size:156mm*156mm
Solar Cell Type: BOSCH
Solar Cell Efficiency:13.5%

[RJsfishin]

NinerBikes wrote:
wonder how long RJ is staying down in the Q. RJ what model 100 watt panels did you end up going with and specs on them? Mono or polycrystaline?

I'll be here for at least 2 months
They are poly panels, are different from each other, different wattage, specs, but are working great paralleled together. Not sure of make/model, from China.

[NinerBikes]

wonder how long RJ is staying down in the Q. RJ what model 100 watt panels did you end up going with and specs on them? Mono or polycrystaline?

[mena661]

BFL13 wrote:
So a two year old battery could be down 10% in normal service anyway.

And solar could easily mask that "lost" 10%. A couple hours of good sun or all day with crappy sun will more than make up for that difference. And the days you don't have even crappy sun you're gonna be in conservation mode (or firing up the genny) and still won't notice.

[BFL13]

There is a huge difference doing 80-98s on solar from doing 50-90s wrt progressive capacity loss. You hardly notice a thing on solar like that.

You could get sucked in to going way too long getting only to 98% every time and when you finally do get it done to 100, you find that your 100 of what? now is less in AH capacity than your 100 of what it was before.

Eventually your batts lose capacity anyway, so you are just delaying things. Might not be worth the bother. If a battery lasts ten years and that means (according to some definitions) it is down to 50% capacity from new, then that is 5% lost per year. So a two year old battery could be down 10% in normal service anyway.

[mena661]

smkettner wrote:
I don't think it adds as much time as most people think because the charge is more complete with reduced sulfation issues.

That would be reduced stratification issues with lower charge rates. No issues with sulfation at high charge rates. But with most peoples converters (55A or less) and battery types (12V's and GC's), there's no issue at all.

smkettner wrote:
I am thinking if half the amps were used the sulfation issue would be significantly reduced.

No it doesn't. I only charge my bank with a 40 and 55 amp charger. That's 5% and 7% charge rates. Akin to most peoples solar setups. That does not reduce sulfation at all. I still have to do the higher volt finish charging that BFL does (but not as long as he has to though). All the really low charge rates do is induce some stratification (not enough in most cases to matter...does matter on mine though) and save some plate material.

The only times I have NOT had to do the high volt finish charge is when I keep SOC above 80%.

[time2roll]

90% of what? You have posted many times about successive sulfation when going 50-80. By the end of two weeks capacity is measurably reduced.

I am thinking if half the amps were used the sulfation issue would be significantly reduced.

This is the same effect RJ is finding with the 10a solar. For me solar just seems to add capacity. I just have no monitor to quantify it. Could be just perception. Could be less than perfect charge maintenance before getting solar.

[BFL13]

I still find the concept of a higher quality recharge than another recharge to the same SOC in a shorter time hard to accept.

In my ugly graph above you see they all get to 90% SOC but higher amp chargers gets it done in shorter times, even though Vabs is reached at a lower SOC. This is because even though the amps are tapering sooner, they are still higher than the amps of the constant amps of the smaller charger until they meet on the line and after that it is the same. All the time the amps are higher even while tapering is still faster.

Anyway, I just don't have a feel for how the battery has a better recharge if you take longer to get to 90% using lower amps. Are there two kinds of 90%?

[time2roll]

BFL13 wrote:
IMO it is more likely SOC will be in the 90s when absorption starts, due to the low charging rate. Solar has low amps compared with the usual converter size amps, so where you might be at 80% with the converter, it would be much higher in SOC with solar on the same size battery bank.

This is another reason I tend to recommend smaller converters and slower charging even if it takes a little longer. I don't think it adds as much time as most people think because the charge is more complete with reduced sulfation issues.

[BFL13]

The controller only knows the voltage, but the battery knows its SOC, and the battery has a "natural acceptance rate" which depends on its capacity, voltage, and SOC, so the battery decides what it will accept.

The higher the charging rate the lower the SOC when you get to Vabs and vv. My ugly graph shows that clearly. For a typical solar amps of say 15a on a 220AH bank (7% charging rate) you would hit Vabs at about 88% SOC but the same 15a on a 440AH bank would be only a 3.5% rate, and hit Vabs at 90something.

RJ sees 10a on two 12s. Using 220AH that's 4.5% charging rate so it looks like low 90s SOC to me.

[pianotuna]

Hi BFL13,

How does the controller know to "back off"? The only measurement it can check is voltage. The controller doesn't know if it is charging 1000 amp-hours or 10 amp-hours of battery bank.

It may be that absorption voltage has a higher voltage set point (or can be so adjusted) in a solar charge controller--but if is not then it would seem logical to me that the set point would default to 80 to 85% state of charge, just as if it were a converter doing the job.