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winnie avatar image

Quick MPPT Nominal PV Power Question

I'm looking to purchase a Victron SmartSolar Charge Controller 250/100.

I currently have six 12v lithium batteries and four 24v 320w solar panels (4×320=1280 total watts). The 250/100 manual states that the Nominal PV Power for a 12v is 1450 W and that the Nominal PV Power for a 24v is 2900 W.

My question before purchase: Since my solar panels (PV) are 24v, does that mean I could increase my solar panel total wattage up to 2900 W or is it capped at 1450 W because of my 12v batteries running a 12v house electrical system?

To avoid confusion, please note that I DO understand that I would also need to stay under the Maximum Open Circuit Voltage of 250 V (that maximumPV wattage isn't the only concern) and that the SmartSolar Controller is capable of converting 24v PV to 12v batteries.

Thanks for your time. I can't afford to make a mistake here, so I just want to be sure that I can add more 24v solar panels in the future.

MPPT - Solar Charge Controllermppt smart solar
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rslifkin avatar image
rslifkin answered ·

The nominal wattage is based on battery voltage. A 250/100 can output up to 100A to the batteries regardless of panel voltage. For future growth, you can always add a second controller.

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Thanks, rslifkin. The 100A output limit to the battery is certanly important information. For those unfamiliar, the second number on a Victron MPPT is the max output from the solar controller to battery(ies). So 250/100 denotes a 250V Open Circuit Limit and a 100A output max from the solar controller to batteries.

My original question could have been better worded. To clarify, I've included a screenshot of the Nominal PV Power information from the 250/100 manual. I'd like to know if I can add up to 2900W in PV on one 250/100 solar controller so as to minimize the cost against buying another expensive solar controller. As a reminder, my solar panels are 24V but my batteries are 12V (as is the AC inverter I was given).

I really appreciatet any help. Thanks.screenshot-20210429-204632-drive.jpg

The panel voltage doesn't matter. You have max. 100A to the battery.

100A x 14,2V (absorption voltage of the most LiFePO4 batteries) = 1450W

winnie avatar image winnie Matthias Lange - DE ♦ ·

Thanks a lot, Matthias! You're been a big help.

winnie avatar image winnie Matthias Lange - DE ♦ ·

I'm new to this forum and I can't quite figure out how to select the answer Matthias gave as the accepted answer to this question. Also, I don't see an option to reward Matthias with reputation points. I'll keep trying. Regardless thank you, Matthias!

That's because it is a comment to rslifkin's answer but his/her answer is also right.

But if you want I can convert my comment to an answer.

winnie avatar image winnie Matthias Lange - DE ♦ ·

Thanks for the explanation. If you'd like the reputation points, then you could convert your comment to an answer. If reputation points don't matter to you, maybe just leave it as is since any reader will be able to follow along regardless. Thanks, again.