Over paneling an LV2424

[zack6736]

So by what I've read on this forum, one can over panel the inverter and the MPP Solar inverters will only take what they can handle from the panels in terms of watts as long as one stays below the amps and volts. My plan is to string together 12 Rich Solar 200 watt into two series of 6 in parallel. I live in SE Kansas and in the winter we do get down in the single digits, I am using 7 *F as the morning low for figuring volts. Can someone with more experience with the LV2424 tell me if this is feasible or just hopium.
Also purchased an LV6548 I was going to upgrade to, but another member stated to upgrade the panels on the new 6548. So my plans have changed to leaving the 2424 in place powering the koi pond pumps, add more batteries, and also have it power the freezer and a small 110v AC in the inverter shed (11'x4.5') to keep it cool in the summer and heated in the winter (floor, walls, ceiling all well insulated). Now thinking will use the LV6548 to power the house leaving the Central AC and Oven (only 220v in the house) on the grid. The rest of the house put on the 6548, and power it with 20 or 24 Q cell 400watt panels. And batteries of course, ones that will play nice with the 6548 . Any thoughts, suggestions are welcome.
Thank you in advance.

 

[MichaelK]

You really want the solar voltage to be as high as practical, to reduce losses via voltage drop. Rather then wiring your panels 2S6P, I'd suggest instead to wire them as 4S3P. Using Midnight's string calculator, it looks like the max Voc at zero F would only reach 110V. That's well within the 145Voc limit of your unit. https://www.midnitesolar.com/sizingTool/index.php

The MPPs have little or no starting surge, so maybe it will start the air-con, depending on what's it's starting surge is. How many watts does the air-con you are expecting to use demand?

 

[zack6736]

Thanks for your response. Will do the 4s3P as you suggest. The AC I thought was 950 watts but when I look now I find 1150 watts. My pump pit is pulling 535 watts 24/7. I can shut down the waterfall pump at night if I have to. The freezer pulls 3.3 KWh a day.

 

[MichaelK]

Thanks for your response. Will do the 4s3P as you suggest. The AC I thought was 950 watts but when I look now I find 1150 watts. My pump pit is pulling 535 watts 24/7. I can shut down the waterfall pump at night if I have to. The freezer pulls 3.3 KWh a day.

At first glance, I think loads of this size are going to be to much for a little LV2424. The ac, pump, and freezer all happening to be on at the same time is going to be almost 2000W. I think getting your LV6548 online would be the better option.

Shop locally for panels. You can find panels for 4W/$ the further south you go.

 

[zack6736]

Thanks for your response. Will do the 4s3P as you suggest. The AC I thought was 950 watts but when I look now I find 1150 watts. My pump pit is pulling 535 watts 24/7. I can shut down the waterfall pump at night if I have to. The freezer pulls 3.3 KWh a day.

 

[zack6736]

I'm confused on figuring the amps. You take watts and divide by volts, correct? Is this total watts of the array divided by one strings volts? This would make the amperage 24.6 by my figures. (2400/97.2) Just trying to get a handle on this before moving onto the 6548. The midnite solar calculator came up with 29.4 amps?

 

[MichaelK]

I'm confused on figuring the amps. You take watts and divide by volts, correct? Is this total watts of the array divided by one strings volts? This would make the amperage 24.6 by my figures. (2400/97.2) Just trying to get a handle on this before moving onto the 6548. The midnite solar calculator came up with 29.4 amps?

What you have to remember is that the MPP has what is called an MPPT controller built into it. What that means is that it acts as a transformer, taking the incoming raw low-amperage, high voltage solar power, and transforms it into higher amperage charging current at the required battery voltage.

The MPPT controller "decides" what voltage to feed to the batteries to maximize the amperage. When the battery is low, it might start charging at somewhere around 25-26V, but as the battery fills, will raise the voltage to 28-29V (depending on settings) till the battery is completely full.

So, looking back at the Midnight chart above, what you see is that the raw solar comes into the controller at 29.4A at 81.6V and leaves the controller to go into the batteries with 83.3A at only 28.8V. So, because of the MPPT function, you are getting almost 3X the number of amps.

Contrast this with an older, first generation PWM controller. It acts solely as an on/off switch, so the 29.4A coming in is 29.4A going back out. If you were using an PWM you would have been better off wiring them 2S6P so you won't be wasting all the extra volts.

 

[zack6736]

Thanks MichaelK, learning more as I wade deeper into solar. Didn't know exactly WHY I was reading and told by a friend to be sure the inverter is an MPPT, now I do.

 

[MichaelK]

Thanks MichaelK, learning more as I wade deeper into solar. Didn't know exactly WHY I was reading and told by a friend to be sure the inverter is an MPPT, now I do.

Got to remember the terminology. Your MPP is an AiO, an "All in One", meaning it's a MPPT controller, an inverter, and sometimes a charger, all in one box. If you were building a component system, you could also include a MPPT, a charger, and an inverter, just adding the pieces individually. That's what I have.

 

[zack6736]

Got to remember the terminology. Your MPP is an AiO, an "All in One", meaning it's a MPPT controller, an inverter, and sometimes a charger, all in one box. If you were building a component system, you could also include a MPPT, a charger, and an inverter, just adding the pieces individually. That's what I have.

Thank you. I'll stick to the AiO inverters. The 2424 is currently online with upgrades to increase the panels as discussed, and adding two more LiFeSO4 batteries. The LV6548 still in the box waiting to be hooked up, but need the panels and the batteries, rack, etc. Hoping to make this system as hands off as possible so the wife can just flip a switch and have power. She's skeptical about solar being dependable as the grid. LOL.