E-bay cells solar panels

[sandovalch]

Just wanted to know how everyones e-bay cells solar panels are doing. Does someone already have output data.
I'm asking, because my output is lower than expected. I have 36 cells in series. I've already built 13 panels and I'm getting only 20Amps at 14Volts for all of them in parallel in a 12V system. My panels are 14m from my charge controller and I'm using a AWG4 cable.
Has anyone better output? Maybe I'm having a heat buildup problem?

[fishfarm]

I'm getting about 70% of rated power. My panels have 210 cells and per specs should generate 285 watts peak. My measurements give me about 200 watts each. The details are located in this section (near the bottom):

http://www.fieldlines.com/story/2005/1/7/204547/8060

[picmacmillan]

 my ebay cells are working fine..i get 3 amps per panel and 15.5 volts or better..i like them and will order more..

 below is a post by internetfred ...it may explain your issue...

 i was wondering if one of your panels or more may be weak...this weak panel will dictate the power from the rest....i also don't know if 14 volts is good enough to charge batteries, it is at 14 volts but you have losses due to a bunch of different factors.....read the post below and see if it may help you...

OK, The more panels in parallel the higher the current, the more in series the higher the voltage.

 The cell size= amps - any cell regardless of size produces a given voltage and for most cells that happens to be around .500 vdc. or ½ a volt.  

  And the size of the cut cell indicates to current. All the cells I have are rated for .500 vdc or ½ volt @ 3 amps. This means that any cell hooked in series is doubled in voltage. Any cell hooked in parallel with another cell is doubled in current or amps. Example; 2 in series=.5+.5=1vdc -> 2 cells in parallel will produce 1/2vdc and 6 amps.

 It does not really matter how you hooked them up provided that, no matter what you must meet the charging voltage or your batteries and the controller.

 This is why when you look at most installations, you will see that 4 panels are hooked in series and then all the rest are generally hooked in parallel to increase the amps only after the charging voltage has been met.

 Most installations use both series and parallel hookups. As far as matching is concerned. Again this is a simple case of the size.

 It is best to match the main panels to produce a charging voltage and then you can use mismatched panels to cover the current in parallel. The smallest size panel in any series will be the net result of all the output (even if the other panels are larger, the smaller panel will dominate. However in parallel it does not care and just adds the current. This is why the matched panels are used for compliance for charging voltage and the -don't care about size dimensions panels are placed in parallel. Makes sense?

  Now as far as how many cells you put into a panel in series is as far as I am concerned totally flexible based on this above information. So, here is the criteria to help you decide quickly how to make a panel.

 First and foremost is the controller.  

 What does the controller require to keep the batteries charged no matter what? I like to be a bit above this by a factor or 3 or more. That way the charging voltage is always met even in a cloudy day. A rough estimate would be about 28-33vdc or slightly higher. This would also allow for compensation for losses. (wire resistance, controller heat and internal losses for conversion etc).

 In my panels I have 28 cells hooked in series, this produces .500 x 28 = 14 vdc. And I hook 2 in series this us 28vdc. The controller voltage is met. The battery charging is met. And produces 3 amps. The controller will later convert the voltage and current to produce a full charge voltage of about 13.8 vdc and increase the amps from voltage not used during conversion. It's hinged on what the controller requires and can put out.

 Now here is the interesting part. Since the charging voltage and controller voltage has been met the rest of the panels (10-20) are put into parallel. Increasing the amps way up. In this case, 3ampsx10 panels=30+ amps or 3ampsx20panels=60+amps. @ 13.8 x 30amps= 414 watts or 828 watts. The neat part about my panels is that for some reason for which I can't explain is that my panels are putting out 16.5vdc @ 3 amps each giving me a total of 49.5 watts each panel.  

 In my case I have already produced 12 panels and am continuing to create more as we speak. I figure I have enough to make about 20 or so panels.

  Each panel produces You can also opt for hooking a large majority of panels in series to produce 128vdc @ 3 amps and then let the controller sort out the amps. It is more efficient and produces less loss. But the expense of the controller is the question.

 Hope some of this makes sense and clears it up.. I wish you good luck and keep us informed.http://www.internetfred.com ->> Encourage alternative energy use!![ Reply to This |  

http://www.frecklefarmloghomes.com

  hope this post helped....pickster

[sandovalch]

OK, I have read the post by internetfred many times and have tried the things he explains with my panels. But when I hook 2 sets of 2 in series and the rest in parallel, the voltage increment is very little, perhaps 1 to 1.5V, and the current drops to 18A. All my readings are while charging the batteries, meaning voltage after the charge controller and charging Amps. So I have seen no advantage in cabling some of the panels in series.
If I choose to leave them in parallel the Amps increase to about 22.
The strange thing is that while charging the batteries I turn on an appliance (500W/110V) the charging Amps increase to about 27A.
I have also tried to cool down the panels spraying water on them and also the Amps increase to about 23A.
I believe I have a heat dissipation problem with my panels. I used 1/2" plywood as backing.

[sandovalch]

If you are getting 70% of the rated power from each panel that is more or less what I'm getting. I'm getting 66% percent. What wire gauge are you using from the panels to the charge controller?

[sandovalch]

Are your reading 15.5V open circuit? And 3A short circuit? Because my panels produce 19V open circuit and 3.1A short circuit.

[picmacmillan]

i just put my volt meter on volts an then switch the red wire to the 10 amp hole and touch it back to the red wire on my panel...pickster

[sandovalch]

picmacmillan: have you tried setting up your panels the way internetfred explains? When I hooked them up that way I did not get the high voltage he says. I can explain it the next way: you add up all your voltages and divide them by the number of panels in parallel. Meaning:
33V (2 panels in series, with 16.5V before charge controller, 36 cells in series x2)
+
33V (second set in series)
+
16.5
+
16.5
...(9 panels in parallel)
divided in my case by 11 (4 sets of 2 in series and 9 in parallel)
= 19.5V. But this is in theory! I was getting about 15.5 to 16V before the charge controller and my Amps were down, because I was missing 2 panels in parallel.

[iFred]

You have either a bad cell or a bad wiring problem, take your pick. Go through the wiring very carfully. I found one like this one day that freaked me out, found out that I had reversed and wired wrong one of the cells in the series of cells.

[iFred]

YES, he is...

The voltage is 15.5 and the current is 3a short through the meter. this was done as a fast test to make sure each panel puts out the max. though this condition normally would be a bad thing to do, I suggest it only to find problems. make sure your meter has some form of resistance internal or that you know it can handle the current. most newer 10 amp dc meters can and have an internal resistance. Basically your going to dead short through meter. If your not sure then add a known resistance in series with the panel. Caution should be obeyed when dealing with amp checks. know what your doing.

[iFred]

IF you are getting 15.5 vdc at 3 amps per panel, then you should get 28-30vdc with two in series no matter what and at 3 amps, if your not then your doing something wrong! Check your wiring. The positive output on one panel connects to the negative of the second panel. You should then have two wires, a positive and a negative.

Two panels in series of 15.5 volts each will give you 31 vdc, Typically however there is some losses, which is acceptable. So in this case around 28-30 volts is good. The total amperage will be 3 amps for both panels because they are in series. So 3a @ 30VDC = 90 watts for the two panels in series, and that is what you should get regardless of the configuration of 56 cells or how you wire them. What I am trying to tell you is that you want to configure the proper voltage for your controller and meet "no matter what" the charging voltage and be higher for cloudy days.

So, in this case - My controller says it handle 32 vdc without issue. So the idea is, give it 28-30 vdc and let it handle charging the batts at the lower voltages and current. The unused voltage between 15.5 on cloudy days and 28-30vdc on sunny days will be converted within the controller to current, increasing the amps to the batts during charge and doing the conversion automatically. Is sweet, it works, it's been tested.

[sandovalch]

I have now a total of 13 panels. I tried putting 2 sets of 2 in series to get up to 30V 3A each and the rest I left in parallel. I only got 15V with all of the panels connected and about 18A.

Each of the individual 32 cells panels I checked for voltage and Amps and almost all of the provide 2.9A at 19V.

Is it possible that my cable going from the panels to the combiner box is wrong, I use 14 AWG?

I cable every 2 panels in parallel to the combiner. This means that for 13 panels I have 7 cables going into the box. From the box to the charge controller I use 4 AWG cable, 14 meters.

How many panels have you produced and which configuration do you use?

[ghurd]

Forgive me if this is too obvious.

Are the batteries about fully charged?

Full batteries, or a small battery, and the charge controller will slow the amps to the battery.

This would explain why the current jumps to the expected output when an appliance is turned on.  The battery voltage drops and the controller sends more amps to the battery to make up for the appliance.

It sounds like everything is working properly if the battery is almost full.

G-

[sandovalch]

Yes, I think you are right. I checked my hole installation today and tried everything. And yes, when I turn on an appliance the Amps jump to a normal current for the amount of panels. I guess every time I returned from home at 1 o'clock my batteries are nearly fully charged, thats why I always saw less charging Amps than expected. Nevertheless I will leave 2 sets of 2 panels in series just for "meeting the charging voltage".

Thanks to all! And happy energy producing!

[ghurd]

I believe you should have all of your 36 cell panels connected the same, in parallel.

It is my fault if my previous comments have you confused.  I intended to say in some places, sometimes, 40 cells could be better than 36 cells.  I did not intend to say 72 cells are ever better than 36 cells.

The 36 cell arrangement is great.  The very minor gain of 2- 36 cell series panels would be a much much greater gain if placed in parallel.

About meeting the charging voltage...  If the cells can not meet the charging voltage, the amps they can produce is very small.

Rough example (very rough)...  

With 2- 50w PVs capable of 2.5a (average) for 5 hours per day.  They give 25ah/day.  In series they only give 12.5ah/day.

A very bad day comes along. One PV can not make charging voltage.  2 can.  But, they can only make .2a for 3 hours on such a day.  Or only about 0.6ah.  The battery would have been better with 25ah yesterday from parallel PVs, almost 42 times better.

Using 4 PVs (2 sets of 2 in series) with a total of 13 PVs, the output on good days will be 18% better.  On very bad days, the total output will be very small and insignificant.

It is better to have 118% on Monday, nothing on Tuesday, and 118% on Wednesday.

Put them all in parallel.  There will be power to use everyday.

G-

[ghurd]

Afterthought,

If the batteries are full by 1 o'clock, you are probably making more power than you are using.

Try a heavier load on the system.

Where are you? Northern or Southern hemisphere?

There is more PV power available in the summer, usually much more.

G-

[sandovalch]

Thanks for the advice.

I am in Guatemala, Central America. And I probably have 80-85% sunny days here. I am still in my tryout phase and still producing 36 cell panels. Since I have cabled my house by myself I am able to connect each of the house circuits separately. So far only the "big" loads of my kitchen are not in the ALT energy system, the rest of the house is. I have changed everything to fluorescent lighting and efficient consumption and apparently, as you say, I am producing more power than I'm using, for now.

But my system is still small and I'm planning to get more batteries so I have more backup for cloudy days. So far what I'm producing in the first 6 hours of the day I have consumed by night, because my battery voltage drops to about 12.20V.

I assume farther up north you need more cells in series to compensate the lack of sunlight and as you say I will probably change my system back to 13 panels in parallel.