Need help in refining my first attempt
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elesaver
Solar Expert Posts: 185 ✭✭
OK, after beginning to learn a bit, I have continued with my attempt at a small solar plan at the barn. It is not working as I thought it would. My plan is to use the solar power to run some box fans to cool the livestock. When I attempt to run the fan for the day, the batteries are depleted too much. The batteries tested at 12.54 at the beginning. The alarm on the inverter was going off at 4 pm so of course I turned it off. I failed to test the batteries at that moment. The fans (2 of them) use 5 amps/hour. I know the inverter would use some power but for such a small demand, I had expected the fans to operate from noon until 7 pm. There is direct sun on these panels for 45 hours/day. Here's what I have in the set up:
3 ea 12V batteries in parallel with 248.6 Ah
1 ea modified sine inverter, 2000W with 4000 peak
3 panels all 12V but there is no sticker on the back of any to know the specifics
1 10 amp controller pwm
I bought these 3 panels a long time ago and used them for a gate opener. In actually physical size, they are not large. Two of them are about the same size as the one larger one but it is not as large as the dimensions I've seen for panels for sale at N. AZ site. I did not count the cells so I can't report that at this moment. I do not know how to test the amp output.
So, "help me, Wanda." I don't know what adjustments I need to make OR if I just expected too much...or both?
3 ea 12V batteries in parallel with 248.6 Ah
1 ea modified sine inverter, 2000W with 4000 peak
3 panels all 12V but there is no sticker on the back of any to know the specifics
1 10 amp controller pwm
I bought these 3 panels a long time ago and used them for a gate opener. In actually physical size, they are not large. Two of them are about the same size as the one larger one but it is not as large as the dimensions I've seen for panels for sale at N. AZ site. I did not count the cells so I can't report that at this moment. I do not know how to test the amp output.
So, "help me, Wanda." I don't know what adjustments I need to make OR if I just expected too much...or both?
1st system: 24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V fforklift batteries in series 938 aH, (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)
2nd system: 24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4)
2nd system: 24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4)
Comments

Re: Need help in refining my first attempt
Sounds like you are expecting to much, 5 amps @ 120 V = 600 watts. Run that for an hour it is 600 WH. or 0.6 kWh.
Sounds like you need much more panel, if it was big enough it would run the fans and charge the batteries for late in the day. I don't think I would want the batteries left "flat" even overnight.
Have you tried to charge them another way (generator or grid) and see how long they last? 
Re: Need help in refining my first attempt
Math.
248 Amp hours of which 124 is usable max. Times 12 Volts = 1488 Watt hours at best. Convert to AC and allow for inverter consumption: about 1.2 kW hours.
5 Amps of 120 Volt fan is 600 Watts. Divide 1200 by 600 you get about two hours run time. Any extension of this is due to PV contribution.
Problems builtin:
12 Volt system. Inherently less efficient than higher Voltage.
Three batteries in parallel. Likely to share current inefficiently.
MSW type invert. Will cause motors to draw more current, further reducing efficiency and increasing power usage.
Unknown panel specs. Could be anything.
10 Amp PWM controller. Limits panel output to 10 Amps even if they were 140 Watt panels capable of over 20 Amps. Insufficient for charging 248 Amp hours of battery.
There's very little chance this setup will do what you want. 
Re: Need help in refining my first attempt
Now don't that beat all? I already had the batteries, panels and inverter before I found this site. People on here are talking about doing such grand things. My little ditzy fans seemed like an easy place to start. At this point in time, I don't think I want to start all over again so...is there a way that I can adapt what I have? Solar_dave says that perhaps more panel would help. I could get a couple more panels that could be used in a new system when I'm able to begin again. I could get offgrid panels that are 12/24V. A true sine inverter is something I want but not at this time. (Cash has left the building.) Then, I could get a higher amp controller plus more battery amps. I've read that it's not good to mix batteries so I'd have to get the kind I have. They are cheapies but seem to be able to work if I get the other things right. I could get 3 more batteries so that would double the Ah. I want to purchase the equipment that can be put to use on a "good" system...mppt controller, etc. Would you mind suggesting corrections or if you think I'd be well served to start over, I can handle it. Not pretty, but I can handle it. Thank you for your help.1st system: 24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V fforklift batteries in series 938 aH, (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)
2nd system: 24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4) 
Re: Need help in refining my first attempt
If you can add enough PV to offset the power use while there is still sun available then the batteries would only have to carry the load once the sunlight could not longer manage it. Depending on how good your insolation situation is that might be 5:00 PM to 7:00 PM. But again that charge controller would be choking you off: 10 Amps @ 12 Volts is basically 120 Watts and the load is 600 Watts.
No easy, cheap solution here. But when is there ever? 
Re: Need help in refining my first attempt
Got it. I'll look into a higher amp charge controller and see where that takes me. Thanks again.1st system: 24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V fforklift batteries in series 938 aH, (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)
2nd system: 24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar minidc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4) 
Re: Need help in refining my first attemptThe fans (2 of them) use 5 amps/hour.
That would really compound your problems. I don't think that's what you mean. Amps is a rate. Amps per hour is a rate of a rate. I think your fans are drawing 5 amps.
If your fans were drawing 3 amps at noon, and 8 amps at 1 PM, and 13 amps at 2 PM, and 18 amps at 3 PM, you would say that the current was increasing at 5 amps per hour.
vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i 
Re: Need help in refining my first attemptI've read that it's not good to mix batteries so I'd have to get the kind I have. They are cheapies but seem to be able to work if I get the other things right. I could get 3 more batteries so that would double the Ah.
Let the knowledgeable guys correct me, but I believe "not good to mix batteries" is referring to age not "kind". You don't want to mix old batteries and new batteries. It will ruin the new ones. When you replace the batteries do them all at once is what I've been told. 
Re: Need help in refining my first attemptAlaska Man wrote: »Let the knowledgeable guys correct me, but I believe "not good to mix batteries" is referring to age not "kind". You don't want to mix old batteries and new batteries. It will ruin the new ones. When you replace the batteries do them all at once is what I've been told.
Actually both, and for the same reason.
An AGM and an FLA will not have the same charge characteristics even if they are the same Voltage and Amp hours.
Two (or more) of the same type of battery but of different capacities will not charge the same.
Two 'identical' batteries of different ages will actually have different real capacities, and so the same thing happens.
The greater the differences due to whatever reason (age, capacity, type) the worse the results from mixing. 
Re: Need help in refining my first attempt
It's best to do most of your power consumption calculations in watts, since power calculations in amps don't necessarily give any insight as to what voltage you're using for your calculations.
5 amps @ 12VDC is a 60watt load (5A * 12VDC = 60W). As many folks have already stated, 5 amps @120 VAC is a 600watt load (5A * 120VAC = 600W = 50A * 12 VDC). Before any of the graybeards here can troubleshoot your situation, they'll need to know all units used in your calculations. That being said, even I (a newbie, albeit one who has learned much in my time on this forum) can see that there's a chance that you never considered the difference between amps @ 12VDC and amps @ 120VAC.
ETA: Your original post said "some fans." How many is "some," and what is the wattage rating of each fan? If you can get accurate watts used (using a KillAWatt meter is the easiest way to find this), so much the better. 
Re: Need help in refining my first attemptHere's what I have in the set up:
3 ea 12V batteries in parallel with 248.6 Ah
Is that 248.6 AH per battery for a total of 745.8 AH
OR
a total of 248.6 AH which would be ~82.9 AH per battery? 
Re: Need help in refining my first attemptIs that 248.6 AH per battery for a total of 745.8 AH
OR
a total of 248.6 AH which would be ~82.9 AH per battery?
I sincerely hope it is the latter as that is bad enough. Were it the former he'd have about 3.8 kW hours of AC power available and the fans would run for 6 hours. 
Re: Need help in refining my first attempt
I hope that it is the latter as well, but if it isn't, then I'm thinking that he's really in a deficit charging scenario. 
Re: Need help in refining my first attempt
<<snip>>
3 panels all 12V but there is no sticker on the back of any to know the specifics
1 10 amp controller pwm
I bought these 3 panels a long time ago and used them for a gate opener. In actually physical size, they are not large. Two of them are about the same size as the one larger one but it is not as large as the dimensions I've seen for panels for sale at N. AZ site. I did not count the cells so I can't report that at this moment. I do not know how to test the amp output.
Folks on this forum might be able to guesstimate the rating of the solar panels you're using, if you can provide an accurate description of the dimensions and appearance of your panels. The dimensions will provide the area receiving sunlight, while the appearance description can help figure out how efficient they are (an accurate appearance description can help in figuring out whether your panels are amorphous {low efficiency}, polycrystalline {reasonably efficient} or monocrystalline {most efficient with current technology}).
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