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Old 09-27-2017, 09:08 PM   #1
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Solar battery charging graph (volts)

2017 19' 160w solar. Eagle, ID. Dual 6v wet cell.

No current used except the about 0.18amp dark current (and about 0.002amp instrumentation), which is drawn unless the main battery switch is turned off. Trailer parked, and this graph is typical of the day-to-day charging with only the dark current used

You can see the battery discharging due to the dark current 'till the sun gets on the panel about 7:30 in the morning and the voltage then increases to about 14.4 and, as the manual says, "Bulk/Absorption Charge @ 25°C: 30 minutes every morning. Applied for 1 hour if the battery voltage drops below 12.3 volts". After that it goes (I think) into float mode 'till about 5pm when the house shadow covers the panel and its output drops to zero and the whole process starts over.
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Old 09-27-2017, 11:51 PM   #2
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How does the controller know when to do the bulk/absorption charge? Does it have an internal clock? Or does it measure the duration/intensity of sunlight in order to trigger the charge?
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Old 09-28-2017, 12:08 AM   #3
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How does the controller know when to do the bulk/absorption charge? Does it have an internal clock? Or does it measure the duration/intensity of sunlight in order to trigger the charge?
It depends on the controller. Most start the bulk charging cycle when the battery voltage drops below a set level. Again, most remain in the bulk mode for a preset number of minutes/hours. If, at the end of that time the battery is still below the set voltage, it starts the bulk cycle again. Eventually, the voltage is high enough that the controller enters the absorption mode. Depending on the controller, it may stay in that mode for a preset amount of time, recheck the battery voltage & repeat, or just switch to the float mode at the end of a preset time.

Some controllers, such as the Blue Skies Sun Charger 30 are completely adjustable, both voltages & times for each stage, while others such as the GoPower controller are preset & may only have a choice between AGM & Flooded batteries (which sets the voltages for each stage). (Although the latest version of the GoPower controller does allow the user to run an extra Absorption cycle.)

None that I know of check the solar panel input. If there isn't enough panel output, most controllers just stay in the bulk mode (although since there isn't enough power from the panels to fill the batteries to 80%, they won't be overcharged).
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Old 12-07-2017, 07:24 PM   #4
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Originally Posted by Earl View Post
2017 19' 160w solar. Eagle, ID. Dual 6v wet cell.

No current used except the about 0.18amp dark current (and about 0.002amp instrumentation), which is drawn unless the main battery switch is turned off. Trailer parked, and this graph is typical of the day-to-day charging with only the dark current used

You can see the battery discharging due to the dark current 'till the sun gets on the panel about 7:30 in the morning and the voltage then increases to about 14.4 and, as the manual says, "Bulk/Absorption Charge @ 25°C: 30 minutes every morning. Applied for 1 hour if the battery voltage drops below 12.3 volts". After that it goes (I think) into float mode 'till about 5pm when the house shadow covers the panel and its output drops to zero and the whole process starts over.
Thx for posting this plot, Vermily. But what charging amperages are associated with it? I'm asking because I am unhappy with my first day charging amperage rates on my identical setup, in the week old 5.0TA we are roundabout ferrying home. We are at Pismo Beach, clear day, no shadowing of the array. Admittedly not optimally cited, with the sun not much more than 25-30 degrees above the "horizon" of the array. But our max amperage was ~1.4, which SEEMS low to me. I can see no other problems, and if I do the arithmetic, the 6-7% increase in battery charge over the course of the day seems about right. I just hoped for more.

I know there's a litany of checks to exhaust all of the potential problems, but I didn't bring a ladder expressly because it seemed that ETI QC would make the probability of the boners listed in the manual quite small. But I DID bring my multi-meter and could make a FEW checks, standing in my truck bed.

Any thought including perhaps that such an angle of incidence COULD reduce power by over 85% from theoretical max?
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Old 12-07-2017, 09:26 PM   #5
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Yes, the T/A has a 6 degree slope towards the back. When I have the option I always face her north, second west, third east, and south last. Having a portable panel helps 5+ amps. The ability to tilt your panels will increase your output 30 to 40 percent, real bang for your buck and having 2 400 Ah AGM would not hurt.
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Old 12-08-2017, 06:16 AM   #6
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Bob, what was the State of Charge, 90%, 95%, etc. On my non ETI solar, the amperage varies as the SoC varies. If the batteries are just about full, the charge rate drops way down. Something like, if I'm only down 3 amps, the controller will not send 8 amps to the batteries. To get an idea of what a max rate would be I need to discharge the batteries some, like running the fridge on battery for a few hours.

Try dropping it down 20-30 ah and see what you get. You may also get more of an output if you have a higher draw. Put the fridge on battery so there is a higher load on the batteries, I suspect you'll see a higher output rate from the controller.

I've read the output for a flat mounted panel can drop as much as 2/3 in the winter, it may differ depending on where you are. If it's sunny today, I'll see what I get out of my 160w.
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Old 12-08-2017, 10:04 AM   #7
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Bob, what was the State of Charge, 90%, 95%, etc. On my non ETI solar, the amperage varies as the SoC varies. If the batteries are just about full, the charge rate drops way down. Something like, if I'm only down 3 amps, the controller will not send 8 amps to the batteries. To get an idea of what a max rate would be I need to discharge the batteries some, like running the fridge on battery for a few hours.

Try dropping it down 20-30 ah and see what you get. You may also get more of an output if you have a higher draw. Put the fridge on battery so there is a higher load on the batteries, I suspect you'll see a higher output rate from the controller.
I've read the output for a flat mounted panel can drop as much as 2/3 in the winter, it may differ depending on where you are. If it's sunny today, I'll see what I get out of my 160w.
Low. 51-59%, at 12.0-12.2 volts. And as would then be expected, "Max boost" helped out not at all. Other posters have made me realize that I had unrealistic expectations for a low angle of incidence, in the winter.
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Old 12-08-2017, 10:33 AM   #8
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Low. 51-59%, at 12.0-12.2 volts. And as would then be expected, "Max boost" helped out not at all. Other posters have made me realize that I had unrealistic expectations for a low angle of incidence, in the winter.
Then I guess that's all it is. Won't be able to see anything meaningful on ours today, it's clouded over with Texas's snow coming in tomorrow.
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Old 12-08-2017, 10:38 AM   #9
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The low angle will make quite a difference. I have 2 160 watt panels on the roof, and with the batteries at around 80%, was getting a little under 5 amps from the GoPower controller during the early morning. I added my portable 160 watt panel (aimed at the sun) & it went up to 13 amps.

During the summer with overhead sun, I typically got 14 - 16 amps from the overhead panels until the controller dropped to the absorption stage.

The GoPower "Boost" button that restarts the absorption stage will not help if the amperage isn't available from the panel. Even then, it the batteries are near full, they will not accept the additional current even if it is available. The final 20% of charging will always take a long time, no matter what the source. That is one of the advantages of solar. Running a generator to get the final 20% wastes a lot of fuel.
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