Solar Panel System Troubleshooting - Charging Battery

[Tom.G]

re: post #88
@Wolst73 Excellent data, but a few questions remain regarding the 0.12A and the 0.35A you measured from the panel.

In several ways, the numbers don't seem to compute.
For instance you have a 19V panel that has an open-circuit voltage of 12V. However your post #72 states 19V output.

Voltage of panel showing about 19v.

The short-circuit current is rated 1.23A but reads or 0.12A (or 0.35A).
Based on your present numbers, the internal resistance of the panel is 99 (or 35) Ohms, making it a 1W to 3W panel.

1) What was the panel orientation relative to the Sun when taking the readings? (directly facing the Sun? flat on the ground? facing due South? Other?)
2) Did your shadow, or another shadow, fall on the panel while taking readings? Even on a corner of it?
3) Time of day the readings were made?
4) Anything else that may or may not describe the situation?

Part (much?) of the descrepencies may be attributable to Latitude, time of day, and partially cloudy weather.

I hope @jim hardy can come up with some more queries for all this. He is much better at digging up the patience for detailed instructions than I am!

 

[Wolst73]

1) What was the panel orientation relative to the Sun when taking the readings? (directly facing the Sun? flat on the ground? facing due South? Other?)

1. Tried to aim the panel directly at sun to get the initial 0.12a reading. The 0.35a reading had the panel laid a bit flatter to the ground but high enough to get to the terminals.

2. No shadows other than clouds going by.
3. Readings were about 1:30pm.

Any other reasons why the output would be so low. Panel is slightly dusty??

 

[jim hardy]

@Wolst73 Excellent data, but a few questions remain regarding the 0.12A and the 0.35A you measured from the panel.

The difference is curious. I attributed it to variation in sunlight.

Fact that neither short circuit approached what the panel should do, 1.2 amp, shouts "panel"
and his open circuit of 19 not 22.4 shouts "panel"
and that panel terminal voltage drops from 19V at zero current to around 12V at just 0.07A shouts "panel" , that's not even a watt !

so i yielded to the old practical adage
"There comes a time in every project where you have to shoot the engineer and get on with it"
time for me to step aside.

I think we all 'synergized' as a group and did pretty good troubleshooting. We have a lot of evidence pointing to "panel" .

All i did was maybe help a little bit with communication... that was a big part of my job my last twenty years.

old jim

 

[Wolst73]

I will repeat tests next weekend. Hopefully be more of a normal sunny day then.

P.S. Jim, I ordered a 3 amp dc panel meter as per your suggestion. Went a bit bigger just in case I need the extra amp down the road. Toys! (wife is starting to question my sanity).

 

[Tom.G]

Maybe I missed it, but what is the make and model of the solar panel? Is there a link where the datasheet can be found?

I strongly suspect the panel is under-powered for your use, by a factor of two to six. Could be a defective panel or just the wrong model (too small.) Since there are too many variables that we can't control for the measurements, all we can do is attempt re-engineering the system from the data sheets. No guarantees though! Also realize that we are working at the best time of year for solar power. Winter will double or triple the needed panel size for the same lights-on time.

Other approaches I can think of is get a duplicate panel and compare those readings with the existing panel. If the new panel is substantially better, return the existing one as defective. If the readings are similiar, connect the two in parallel, Red to Red wire, and Black to Black wire. This will double the solar capacity; although that still may not be enough. Alternatively, find a local Solar Power company and see what recommendations they have. (I'm pretty sure they will want to sell you SOMETHING.)

Also, using the site that @jim hardy referenced (http://www.pveducation.org/pvcdrom/properties-of-sunlight/arbitrary-orientation-and-tilt ) the optimum tilt angle for best year-round performance is 72 degrees. i.e. the panel should tilt 72 degrees from horizontal, or facing 18 degrees upward from standing vertical. This will give you approximately equal power in the summer and in the winter. This is based on your Latitude of 48 degrees.

Sorry about all the 'could be' and 'maybe', it's been forty years since I've done any of this Solar stuff.

 

[Wolst73]

Maybe I missed it, but what is the make and model of the solar panel? Is there a link where the datasheet can be found?

Recap: 30A solar charge controller (also have a 10A), 12v 18ah battery (bought new but might be a problem too), 6 3W LED lights hopefully powered for 3 hours per night.

 

[OmCheeto]

I still don't see where we've done measurements for the following configuration:

And with the new ammeter, we could figure out the efficiency of the Luxdrive.

 

[Tom.G]

Well, I did some research and 'back of envelope' numbers with these results.
Panel Azimuth: 180 Degrees
Panel Tilt: 72 Degrees
Nominal panel Current: 1A

The following is for Winter configuration with roughly 6Hrs of sun and clear cloudless sky.
Corrections for:
Low angle during Winter: 0.67 (same value for Summer Latitude mismatch)
Azimuth correction during the day: 0.68
Battery charge Efficiency: 0.8

1A x 6Hrs x 0.67 x 0.68 x 0.8 = 2.18AH per day in winter
If the controller adjusts/tracks the maximum panel power output at around 18V:
2.18 x 18 = 39WH per day in winter.
So you will need two panels in the winter if there is full Sun every day.

For cloudy days corrections are:
High Clouds: 0.83
Med. Cloud coverage: 0.3
"Really, Really Overcast": 0.15 (rain?) 0.15 x 39 = 5.9WH per day

Bottom line is if you want to carry thru from two days of rain you will need at least ten times your current panel area.

For those of you that are willing to check these calcs, here are the references:
http://www.ftexploring.com/solar-energy/clouds-and-pollution.htm
http://www.ftexploring.com/solar-energy/clouds-and-pollution.htm
http://www.pveducation.org/pvcdrom/properties-of-sunlight/arbitrary-orientation-and-tilt

 

[sophiecentaur]

10 ma ? I didnt know they had that kind of resolution

LSD, iirc.
Quite good enough to see if you're doing worse or better.

This will give you approximately equal power in the summer and in the winter. This is based on your Latitude of 48 degrees.

If we are doing garden lighting the demand will (could) be greater (longer) in winter so it may be better to tilt the panel down a bit. (A real world consideration). Adjustment during the early cycle could give the best of both worlds.

 

[jim hardy]

Wow @TomG nice job with those calcs !

it's been forty years since I've done any of this Solar stuff.

you're one up on me - i never have...

Recap: 30A solar charge controller (also have a 10A),

I am curious about "efficiency"
a controller rated 30 amp 12 volt is rated to handle 360 watts
if it's spec'd 99% efficient it is entitled to consume 3.6 watts irrespective of actual load
which does not sound unreasonable , it takes considerable power to charge those gates on big power mosfets
so its idle current might well be ~0.3 amp
and who'd complain about 99% efficiency ?
The question to ask is "99% of what?"

that'd be worth measuring per Om's suggestion
when you get that ammeter and a better panel , try that ten amp controller too

can you return your panel on a warranty claim ?
Sounds to me like it has an internal short that's stealing power , except at zero terminal volts
that would explain the difference in Isc on opposite sides of the blocking diode
upstream of it you got 0.35 amp, that'd be zero across the panel terminals (well maybe a few millivolts across ammeter )
downstream of it you got 0.12 amp , that'd be about ¼ volt across panel
as voltage across panel increases the short steals more and more of your 1.2 amps

Try modelling it as a Norton equivalent: 1 amp source paralleled by 15 ohms ? Where's my slide rule...

 

[Tom.G]

If we are doing garden lighting the demand will (could) be greater (longer) in winter so it may be better to tilt the panel down a bit. (A real world consideration). Adjustment during the early cycle could give the best of both worlds.

That's sort of what I did. With the high Latitude of the installation (48 Degrees), I first optimized tilt for Noon on the Winter Solstice, Dec. 22, then checked the Summer Solstice results. They turned out within a couple percent of each other. At that point I said "the heck with it, optimize for worst case!"

Fudging the tilt in general depends on intended usage of the power. In this case there is no use for any excess power in the summer. If on the other hand this was for domestic usage as a supplement for mains power, then the tilt would be optimized to maximize total annual power. The total-power optimum tilt is accomplished by aiming the panel slightly down from the Latitude of the installation.

 

[sophiecentaur]

If on the other hand this was for domestic usage as a supplement for mains power, then the tilt would be optimized to maximize total annual power.

Absolutely. I'm surprised that people with grown up mains connected systems don't use some manual adjustment to improve their returns from the Feed in Tariff over the year. I'm sure you could get a result for the man hours put in.

 

[vadslram]

Why do you say no? The picture says CYCLE on the side. It is a starting battery.

It doesn't mean motor CYCLE. That is a battery that is used for UPSs and emergency lighting. The cycle count is the number of discharge/ recharge cycles that the battery can do and still keep the rated AH.

 

[anorlunda]

It doesn't mean motor CYCLE. That is a battery that is used for UPSs and emergency lighting. The cycle count is the number of discharge/ recharge cycles that the battery can do and still keep the rated AH.

I stand corrected.

 

[Tom.G]

The cycle count is the number of discharge/ recharge cycles...

Although a useful number, I don't recall anyone mentioning 'cycle count' in this thread. Can you point me to where it was brought up?
Thanks.

 

[Wolst73]

still don't see where we've done measurements for the following configuration:

I will get those measurements this weekend.

I emailed the seller of the solar panel last night explaining the low amp readings we found. They responded this morning "asking for the test date of the voltage(?)Will replace if panel is bad." Are they checking my weather?? I never mentioned any voltage findings just amperage.

Also, I see we are 6 pages into this thread. Just want to thank everyone for their time and advice in helping me out on my little project. Very much appreciated and I have learned a lot (should have bought a clamp meter!). It's a challenge now to make it succeed

 

[vadslram]

Although a useful number, I don't recall anyone mentioning 'cycle count' in this thread. Can you point me to where it was brought up?
Thanks.

When a poster confused the "cycle use" charging information as printed on the battery as meaning it was a motorcycle starting battery.

 

[OmCheeto]

I will get those measurements this weekend.

Another useful measurement would be the resting voltage of the battery each day. I would do this measurement in the morning, before you go to work.
Assuming you have the system set up now to charge the battery, and no lights on in the evening.

I emailed the seller of the solar panel last night explaining the low amp readings we found. They responded this morning "asking for the test date of the voltage(?)Will replace if panel is bad." Are they checking my weather?? I never mentioned any voltage findings just amperage.

I'm still not convinced that there is anything wrong with your panel.
We have too little data, IMHO.

Also, I see we are 6 pages into this thread. Just want to thank everyone for their time and advice in helping me out on my little project. Very much appreciated and I have learned a lot (should have bought a clamp meter!). It's a challenge now to make it succeed

Threads like this actually prompt me to do lots of testing, and figure out what's going on with my panels.
Somewhere in the forum, in a very old thread, I claimed my panels were all putting out 100%, even though they are 25 years old.
One person questioned that, and since I'd never actually checked their output, I kind of shut the hell up.
I did a load test of them on May 2nd this year, and finally figured out how wrong I was.
Their average peak output is only 22 watts. They are rated at 50 watts.

But anyways, in looking for that post I found something in one of the bazillion solar panel threads, which I had forgotten about.

Dollar Store Pumpkin Light Solar Conversion [physicsforums]
Post #8, Oct 2, 2011

From Battery University:

100% depth of discharge on a starter battery = 12–15 cycles

What that means, and probably why Tom.G made the query;

Although a useful number, I don't recall anyone mentioning 'cycle count' in this thread. Can you point me to where it was brought up?
Thanks.

is that, if you've discharged your battery 12-15 times, it is most likely a very good candidate to be turned in and recycled.

Ah ha!
Found that post. {Feb 2010}

ps. My 1981 1991 Kyocera panels are still operating at 100% rated capacity. Trust in quality, not statistics from the 1950's.

Yep, trust in quality. Let's also trust in physics. How do you know the panels are still 100%? Have they been in daily use since 1981?

This is one of the best things about PF, IMHO.
There is always someone around, who will call you on your, ummmm... , male-Bos taurus-excrement.

In my defense, for being a bit late, it was February.

 

[Wolst73]

Assuming you have the system set up now to charge the battery, and no lights on in the evening.

You assume wrong! I didn't think it would be good to have the panel hooked up if it wasn't sending enough charge to the battery. Didn't want to harm the battery any further. I will hook it back up tonight.

 

[OmCheeto]

You assume wrong! I didn't think it would be good to have the panel hooked up if it wasn't sending enough charge to the battery. Didn't want to harm the battery any further. I will hook it back up tonight.

hmmmm... My passport expires in 2 months.
Perhaps I should make my third road trip of the year, and come visit you in Victoria, this weekend.
I have lots of resistors and thingys.

ps. Lovely town, btw. I've been there 3 times, back around 1980.

 

[Wolst73]

I'm still not convinced that there is anything wrong with your panel.
We have too little data, IMHO.

The results from Jim's tests don't convince you? Do you think multimeter is not accurate enough (+\- 2% + 5 for DC current) or perhaps the operator lol? I will repeat them this weekend with both charge controllers (30A and 10A) to see if we get different results. Hopefully will be sunny as its been unseasonably crappy all week.

No response yet from panel seller.

 

[jim hardy]

I emailed the seller of the solar panel last night explaining the low amp readings we found. They responded this morning "asking for the test date of the voltage(?)Will replace if panel is bad." Are they checking my weather?? I never mentioned any voltage findings just amperage.

This should help... tell them

Open Circuit voltage in mid-day sun: 19 (do i remember right ?)
Short circuit current in mid-day sun: 0.12 amp downstream of blocking diode, 0.35 amp upstream (do i remember right?)
Voltage across blocking diode : 0.23V (ditto ?)
Voltage when connected to battery in mid-day sun: 11.8, current 0.07 amp (ditto? )

and i have got myself a Canadian sunburn trying to get this frustrating thing to work.

 

[OmCheeto]

The results from Jim's tests don't convince you?

Nope.
I want to see the results from the test I described in post #97.
From your V3 measurement in post #47, of 19.2 volts, we know that your lighting system is actually only consuming 13.4 watts.

 

[Wolst73]

This should help... tell them

Thanks Jim. That did the trick. They are sending a new panel. Hopefully not the slow boat. Worst case, I'll have two panels to wire together.

 

[jim hardy]

Great!

Meantime try OM's test ?
It'd be interesting to know how much current the led driver sends to those lamps.
As you know, LED voltage is rather constant, related to how many electron volts it takes to make photons of whatever color is the LED.
White LEDS used to use a UV diode that excites phosphors inside the plastic to make visible light. So they were rather high voltage, and i think you measured 19 volts for six of them ? That's probably fairly independent of current.
3.1 volts each? Hmmm that's more like green per these folks..
What is part number of yours, or datasheet link ? I looked all over Cree for 3 watt yard lights to no avail..

https://wiki.analog.com/university/courses/eps/diode-curves

so
It'll be interesting to get a current reading on LED side, too, like OM suggested, and see if it makes its 0.7 amps.. i hope we don't find a perpetual motion machine here...

old jim

 

[Wolst73]

http://www.ebay.ca/itm/262356750301?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Hopefully that link works. They are the warm white 20mm led.

 

[Wolst73]

Another useful measurement would be the resting voltage of the battery each day. I would do this measurement in the morning, before you go to work.

11.67V Thursday and Friday morning. Checked it last night around 7pm and it was 11.76V.

 

[OmCheeto]

11.67V Thursday and Friday morning. Checked it last night around 7pm and it was 11.76V.

Well, that gives us a couple of more clues.
Another handy clue, would be an estimation of what time in the afternoon the panel was shadowed, given that sunset is 9:10 pm.

Interpolating the "State of Charge(SOC)" to "Voltage" table provided by Battery University, I came up with the following equation: SOC = (volts - 11.89)/0.0076
Plugging in the change in voltage, and battery capacity(≈240wh) numbers, I come up with 28.4 watt hours of charge, for yesterday.
Given that you live only 200 miles away, and roughly the same distance as I from the Pacific ocean, and my observations of the color of the sky yesterday, I'd say your panel is working fine.

Of course, with your battery still reading below dead, this is just a rough guess.

Whoa! I see it's already cleared up, up there. We are still under full coastal morning cloud cover.

 

[jim hardy]

probably there's such a table at Batteryuniversity
but i couldn't find it
this one's from

http://jgdarden.com/batteryfaq/carfaq4.htm#ocv_soc

 

[OmCheeto]

probably there's such a table at Batteryuniversity
but i couldn't find it...

Post #21.