LV6548- PV Setup Questions

Espaul

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Joined
Aug 14, 2021
Messages
13
Hello, this is my first build and my first post, so I apologize if I seem completely ignorant. It's because I am.

I am going to be purchasing a MPP LV6548, probably either a set of 24V Ampere Time batteries, and SanTan Solar T-Series 250W panels.

So for the MPP, which has two inverters, here are the specs of the panels/one inverter.
InverterSolar Panel
4000w max250w
18amp Max Current8.27amp Max current
250VOC max pv input37.6 VOC

So, what I am understanding is I'll have to have:
2 in parallel= 16.54Amps.
That's basically the max. What I don't get, is if I want 12 panels total per inverter, are the other 10 in series equal to 376VOC, or half that since they're connected in parallel as well?
 

Espaul

New Member
Joined
Aug 14, 2021
Messages
13
Or perhaps I should just ask:
When trying to size/link PV panels, am I trying to stay within both VOC -20% for cold temps, as well as ISC amps? Or are Max current ratings for aforementioned All in one system not really a factor? A prior post appears to state that an amperage of well over the 18A max is fine, but if a maximum is stated it seems like it would be for a reason.

Any and all help would be greatly appreciated. Thank you!
 

Patrick_Cashman

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Sep 15, 2021
Messages
8
When you put the panels in series, the voltage adds up. So do the total watts. To find the current of the series line, divide the total watts by the total voltage. The 6548 manual has an example of how to do this on page 9.

In your case, the panels run at 33V, with the 38VOC. You can make sets of 6 in series, with 6X38=228V. Working voltage is 6X33 = 198, let's call it 200. The total actual watts of that line will be around 1200, since these panels run at 75-80% of their stated output. So 1200W / 200V = 6A. When you put the strings in parallel, the voltage stays the same across the strings (if you measured from the positive end to the negative end) and the current adds up.

Since the current limit on each PV input is 18A, you could do 3 parallel strings of 6 in series (6S3P) and be right at 18A on the entire solar array. In your case you will have a 6S2P system with 12 total panels and the current in the PV line will be 12A. The example in the manual shows one case of 6S2P on each of the PV inputs, for a total of 24 panels.

BTW I'm in the middle of doing a similar system. LV6548 and panels from San Tan Solar. I read through the manual yesterday to get familiar with the install process.
 

Espaul

New Member
Joined
Aug 14, 2021
Messages
13
When you put the panels in series, the voltage adds up. So do the total watts. To find the current of the series line, divide the total watts by the total voltage. The 6548 manual has an example of how to do this on page 9.

In your case, the panels run at 33V, with the 38VOC. You can make sets of 6 in series, with 6X38=228V. Working voltage is 6X33 = 198, let's call it 200. The total actual watts of that line will be around 1200, since these panels run at 75-80% of their stated output. So 1200W / 200V = 6A. When you put the strings in parallel, the voltage stays the same across the strings (if you measured from the positive end to the negative end) and the current adds up.

Since the current limit on each PV input is 18A, you could do 3 parallel strings of 6 in series (6S3P) and be right at 18A on the entire solar array. In your case you will have a 6S2P system with 12 total panels and the current in the PV line will be 12A. The example in the manual shows one case of 6S2P on each of the PV inputs, for a total of 24 panels.

BTW I'm in the middle of doing a similar system. LV6548 and panels from San Tan Solar. I read through the manual yesterday to get familiar with the install process.
Thank you for your reply! Are you doing off-grid with battery backup I assume?
 

Patrick_Cashman

New Member
Joined
Sep 15, 2021
Messages
8
I'm setting up an RV for full-time boondocking. Well, mostly boondocking. We have the RV, are already full time in it. but want to be free of the restriction of being in RV parks and campgrounds with hookups. At times we'll be moochdocking ( at the homes of family members ) and I'm sure we will stay in campgrounds and parks some of the time, but the main goal we have is to be in more remote locations and not have to depend on shore power. We have a 5500W generator to supplement the solar if the need arises.

Current configuration is 560Ah @ 48V of batteries, and around 4000W of solar. I'm a bit shy on the solar side due to the limitations of the size of my RV roof. I'd like to have enough solar to recharge the batteries in 5 hours, but will need about 10 hours every 3 days to keep up. All theoretical at this point, and will depend on location, sun, weather, etc. We will see how it goes and adjust as needed. Good thing is the LV6548 has a lot of headroom for expansion without adding more control and conversion hardware.
 
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