russ
Solar Advocate
Posts: 63
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Post by russ on Mar 5, 2020 21:46:31 GMT
[...] Since the battery charger is just keeping even with the battery draw, the next step will have to be, plug the killawatt into the inverter and then plug all the electrical stuff into the killawatt, to see what the power usage is, with my electrical stuff. The battery charger is rated at 10 Amps, so I am not sure why it is not slowly charging the battery array past the draw rate. But before I do anything, I will wait another day, tomorrows weather report shows considerably more sun than today. Are you running a 12 volt battery system?
If you are, 12 volts times 10 amps comes to 120 watts. When you figure out your battery draw wattage, you will get a better idea how much power you need to keep the system charged.
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Mar 6, 2020 11:59:01 GMT
After a couple of days of testing, it seems like my new battery charger is unable to charge the battery array sufficiently while the battery array has a power draw.
The other day the battery array was down to 12.2V, as measured by the multimeter. With no draw on the battery array, I let the new battery charger do the charging. The battery charger worked as expected, about ~15 hours later it showed that the battery array was fully charged, and the charger was no longer charging the battery array.
The battery charger is rated at 10 Amps, and the one LCD display, was showing, during its charging cycle, 11 Amps current being used.
The one thing that came to mind, if the battery charger took ~15 hours at 11 amps to fully charge the battery array, which is two 100Ah batteries, what the heck can my solar panel setup do. Over the last four months, I would be lucky to see maybe a steady 7 amps for a couple of hours for the day, and those days were not often enough.
So, I have to come up with a system that helps that solar panel system with some AC->DC power. I will start another thread for some testing that I am doing with that.
This morning I am doing another battery charge session, the battery array is at 12.33V. Started early this morning maybe I will still be up when I can see when the battery charger has fully charged the battery array.
As the weather gets a little more milder, and the snow has disappeared, I will be moving a couple of the solar panels to a better location. Now that I have a better idea of where those sun hot spots are during the winter and summer months. I will be "fine tuning" my solar panel array setup.
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Post by tattoo on Mar 6, 2020 18:17:18 GMT
Guess I will save your time and mine in the future and not bother posting.
Yep that's the best thing to do...............
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russ
Solar Advocate
Posts: 63
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Post by russ on Mar 7, 2020 1:55:16 GMT
[...] array was fully charged, and the charger was no longer charging the battery array. The battery charger is rated at 10 Amps, and the one LCD display, was showing, during its charging cycle, 11 Amps current being used. The one thing that came to mind, if the battery charger took ~15 hours at 11 amps to fully charge the battery array, which is two 100Ah batteries, what the heck can my solar panel setup do. Over the last four months, I would be lucky to see maybe a steady 7 amps for a couple of hours for the day, and those days were not often enough. [...] Typically, battery charger current will taper off as the battery becomes charged. So, the following calculation will be over estimating how much power is needed to charge the battery array.
15 hours at 11 amps is equal to 15 X 11 = 165 amp hours. Probably something more like 100 amp hours, taking the battery charger current tapering into consideration - but this is only a guess.
Your two 12 volt 100 Ah batteries in parallel (assuming they are deep cycle batteries) should not be discharged more than about 50%. That means you have about 100 amp hours of useable battery capacity when the batteries are fully charged. That also means that your 10 amp charger should be enough to charge the battery array up as long as you don't have much of an external battery load.
The big question is how much power are you drawing from the battery array? If you knew this, you could figure out how much power you need to keep your batteries charged.
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Mar 7, 2020 11:45:38 GMT
Thanks russ for your input.
I can add a few bits of information, yes, the two batteries are deep cycle AGM. Since I was using the "full load" approach, I can also state, according to the killawatt, the draw is something like, on the low end, 1.42 Amps, and on the high end it could be 2 Amps.
Today I am going to set up for the itemized approach. In the room that I am doing this experiment, I have, probably 10 - 15 electrical devices. These could be as large as my WD NAS box, or as small as 8 port gigabit switch. I have one computer that gets turned on, in the morning, and gets turned off in the evening, which includes the monitor and the desk lamp, and the external hard drive that is attached to the computer.
This morning I will start with a fully charged battery array, turn on the inverter, add one device, after I measure consumption with the killawatt, then add another device at the appropriate time. This will be a very tedious approach, but I will get a very good idea of the system capabilities, especially in cloudy conditions.
Again, today, it is going to be cloudy, with possible rain. Just as a reminder, 6 panels = 500 Watts.
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Post by bupkis on Mar 7, 2020 12:52:18 GMT
the killowat should be measuring 120vAC amps so the equivalent amps @12vdc is tens time that of AC, ie an 120w/1A/120vAC = 120w/10A/12vDC.
You should measure watts instead of amps! (or multiple amps by 10)
If a device measures 250 watts then I would suggest a .85 factor for the inverter
therefore, 250/.85 = 294 battery watts. converting battery watts to battery amps is divide by battery voltage (12v).
294 watts / 12v = 25 A
A 10A 12v battery charger, that 120 watts, or 1A @ 120vAC = 120 watts
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Mar 12, 2020 12:30:56 GMT
My experiment with the new battery charger running 24/7 just came to an end. This morning the battery charger fan was sputtering and the battery array was down to 12.5V. Normally the battery array would be at around 13.7V, so this morning the battery charger was no longer charging. I guess a new project, figure out what the problem is with the battery charger, or because the unit only cost $16.00, toss it.
I am still trying to figure out a sustainable solution for using some AC power to help the solar panels, in keeping the battery array charged up, while having a draw on the battery array, 24/7.
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