question

The calculator seem correct to me. Four 400W panels is a total of 1600W.

1600W of charging power to your 12V battery results in a charge current of 1600 / 12 = 133A.
The largest charge controller available for a 12V system is 100A, so that is why it's the only result that the calculator presents. You'll be charging your battery with about 1200W (12V x 100A). When the battery Voltage comes up to 14V then it will be 1400W.
1600W of panels is not a bad choice, slightly over the maximum output of the controller, good for overcast days.

On the input side, if you do put all your strings in series for low PV cable current then the 250/100 model is perfect. If you configure your panels in 2 series, 2 parallel then you could use a 150/100.

A 24V battery system would lower the charge current 1600 / 24 = 66A, so then you would be able to use the smaller controllers. But the 100A model would allow you to double up your PV array on a 24V battery system.

Hi @KA1J

The calculator is trying to cover the total W your panels can produce into 12V. You may not need more than 50A to cover your battery charge, and you may want more for loads. But it knows of neither anyway.

Your future plans for 24V would change what it recommends, maybe a /60. But adding more panels & batts changes that again.

Perhaps you should enter the data for your proposed eventual setup, then run with that.

You're limited by the models made by Victron.

If you need more than 150V input, the next step is 250V.

Current in the specs/model numbers is output current.1600W into a 12V system is over 110A, assuming max charge voltage of 14.4V. This isn't affected by panel configuration. Can your batteries handle this?

If it's not too late, consider a higher battery voltage with DC:DC converters for 12V consumers. Most of the Victron controllers are suitable for both 12V and 24V systems, some cover 48V as well.

I haven't run the numbers, but I'm pretty sure that a 100/50 MPPT would run your panels on a 24V battery bank. You'd clip max power a little, but unless you're in a very sunny area, losses will be negligible.

Also, if you upgrade in future, it's ok to add a second MPPT to drive the new panels.

wkirby, JohnC, & Kevgermany,

Thank you for the replies! I can now accept the calculator is working properly, it just didn't seem right that the amps to be dealt with required 100 on the controller.

My solar need at this time is not to power my house, I do want to maintain continuous power for my Amateur Radio and computer via solar. If there's extra power generated, I wouldn't mind powering a refrigerator, but day to day power for my radio station equipment, and power for a refrigerator during power outages is all I am seeking now. At this location I will not be connecting to the grid.

kevgermany asked about my batteries handling 110A @ 14.4 volts. That's a good question. That's something I don't know the answer to. The link I provided above regarding the battery it says for 12V:

Absorption voltage 14.7

Float voltage 13.5

Equalization voltage 16.2

For brevity in this reply I'm not including other available data that might be important, but if you look at the link, that might have the info needed for you to help me. The battery link is: https://www.trojanbattery.com/pdf/datasheets/SPRE_06_415_DS.pdf

I have to wonder if the Victron smart controller allows me to set those absorption/float/equalization values via bluetooth? If not, how is attaining those requirements accomplished?

While I would like a 24V, or better, a 48V system, I don't have any interest doing that at this location. There is nowhere I can get direct sun throughout the day, there are too many trees away from my property line that I cannot have removed or lowered. This is not a great location for solar. I intend to relocate to a location better to have better Amateur Radio antennas and will establish an improved solar system once relocated.

Currently I could add more batteries and go for a 24V system which would be better controller-wise but that would add another $1,000 in batteries, and I'd have to find a different inverter that fits my low RFI/EMF requirements. The inverter I have at this time is: https://www.invertersupply.com/index.php?main_page=product_info&products_id=2560 and it is exceptional in that it creates a sine wave every bit as pure as commercial power, and being a low frequency and high quality inverter, it creates no detectable interference to my Amateur Radio equipment. At 12V, this is perfect for my needs. Finding another inverter that fits these specs @ 24V or 48V along with those batteries is a large expense that is not a requirement today.

If a 250/100 controller is required at this time for me to go with these 4 panels in series and a different arrangement would let me use a less expensive controller, perhaps I would be best off to parallel two pairs of panels and series those pairs, running those to the controller using the 150/100 controller wkirby suggested.

If I go with a 150/100 controller & those series paralleled panels, I've read it is important to parallel high current diodes with each panel to prevent shading on one panel from dragging down the efficiency of the entire system. If that's so, where would my best approach be to parallel the panels considering placement of those high current diodes? Close to the panels and then run the + & - 50' to the controller, or would I be best to run all 4 panels directly to the controller and junction them with the diodes there? Running in series is simplicity, I'm not sure about what's proper with series-parallel configurations.

Also, if I do go with series-parallel, for a 50' run between the panels and controller, what gauge wire would be considered within normal limits?

Thank you.

John, thanks.

Gary