Hello again:
say, I am expanding on my AC300 to the 2nd string of panels for PV2 input.
The panels I am looking at come in at 148.05 volts and 1365 watts for 3 panels.
What I am worried about is the 148 volts comes in dangerously close to the 150 limit.
I live in Minnesota & it gets cold here, so the volts will go up.
I need to use these panels as I am hooking up a large 240v system & these large panels only come as a 10 panel minimum order. So instead of having 3 different brands / sizes up there, figured I would stick with these.
If the 148 volts is too much, then I will have to go with 2 panels, which does not take as much advantage of PV2 as I would like. Two panels would be 98.7 volts & 910 watts.
But I don’t want to have overvoltage errors either.
What do you think?
What is the Vmp and the Imp? I’m thinking that using 4 per MPPT input might work. You’d have to have 2S2P setup, and it would require the extra panel (which it sounds like you’d have to buy anyway), but you’d be well over-paneled without going over the max input voltage.
Vmp is 41.32
Imp is 10.89
Voc is 49.35
Isc is 11.44
Watts = 455
Right now, I have 1200 watts on PV1 of the AC300 & things are good, but I need more power.
So, it is time to use PV2
Don’t want to underpower it, but don’t want to go over the voltage either. I know I can ramp up the amps a bit.
Thanks for getting back to me, appreciate.
am not sure what you mean by a 2S2P setup
thanks
2S2P is a short way to write having 2 in series and then putting two of those in parallel. You’d use 4 panels, the voltage would be less than the 100 volts Voc (for 2), and would have up to the 12 amp limit available.
The thing is that with those specs I don’t know if you’d get much over 1000 watts, maybe 1100, but the Vmp is a bit low and the Imp a bit high for useful overpaneling. I think (I’ve only worked on my system). But you’d likely get that performance for a better part of the day, and better than normal on cloudy days because of the overpaneling.
If I had to get those panels that’s what I would do.
Thanks for the great info:
I decided to possibly go for the 410-watt panels instead.
With the lower VOC, I can get 1230 watts of panel power for the AC300 ( of course you never get what they say)
but it keeps me at 111.36 volts & 13.96 amps when wired in series.
410 watt panels
VOC is 37.12
ISC is 13.96
VMP is 31.35
IMP is 13.08
The problem is when you buy these big panels from anywhere, you have to buy 10 minimum.
I am installing a 240-volt system next year and I need some of these large panels as I only have so much room on my roof, so need to go bigger wattage, not more panels.
So will be buying “X” amount of the large panels for that system & those will have to be the same panels I buy for the AC300 upgrade & the Max upgrade.
That way, I can just get a pallet of those panels. I also want the panels to all look the same on the roof & my brkt system dictates that also.
So that is why I am trying to make this work. I know what I need for the 240-v system, but need to figure the same panels (whatever ones I use) and make them work for the
AC 300 & Max. With limited roof space, I need to get the biggest panels I can as my 240v system can take up to 7500-watt pv input with 500 volt & 27 amps.
So will be getting 12 of these 410w panels, which puts me at 4920 watts, 445.44 volts & 13.96 amps. So that is good. Then need to figure the same panels to the bluetti units.
You got me thinking, so that is good. Deciding on the 410-watt panels work better for the AC300 & also allow me to put 3 more panels to my 240-volt system also. Could only use 9 with the 455-watt panels.
Thanks for getting back to me, appreciate.
That’s quite the set up you’ll have, nice! Happy to have been a thought provoker. 
Enjoy your project.
Thank you so much!
I did see photos of your ground array, very nice!
I attached some photos of my ground array.
The panels look blue in the first pic, but they are black.
take care
You are very welcome. And you have an awesome array setup as well, very nice!
I am using the Renogy’s 450W (I got them earlier this summer). 3 for each PV leg. They were unavailable most of the summer, but just became available online. I got mine from Home Depot but they were unavailable there last time I checked.
VOC=41.25
On the Sunny days, I am getting 2400W (2375-2430W) for an hour and a half window. I can charge 4x b300 batteries about 50% on a typical day. They are slightly overpaneled but that allows me to have that longer period of max input (around 2400W).
Good Luck!
I really appreciate your post
…completely new to solar, and I am no electrician.
Changed outlets & light fixtures …that’s about it
…just purchased the AC300/B300 combo and I want load it to capacity with panels
… very interested in the 250 watt Santan panels you spoke of and I found some used ones at $40 apiece
…thinking about buying 12 of them
- Rated Power: 250W
- Open circuit voltage (VOC): 37.6 V
- Max power voltage (VMP): 30.3 V
- Short circuit current (ISC): 8.85 A
- Max power current: 8.27 A
- Power Tolerance 0/+3%
- Maximum system voltage: 600V (UL)
- Fuse Rating: 15 A
- IP65 Junction Box w/MC4 Compatible Connectors
- Frame: Anodized aluminum alloy
- Weight: 41 lbs.
- Dimensions: 64.95 × 39.05 × 1.37 inches (1650 × 992 × 35mm)
I’m here to learn as much as I can so I can have a power back up
Do you still like your 250W Santan panels?
Forgot to ask
…The Santan panels I’m looking at specify they have a Max power current of 8.27 A ,
…but they don’t specify the IMP
…I’m assuming these are same panels you spoke of?
Those, by the specs, appear to be the same as the ones I bought. And FYI, the max power current is the same as the Imp, so you’re good with that information. I am very happy with these panels. On a day with sun, even somewhat hazy sun, I’ll get anywhere from 2,200 watts to 2,400 watts during peak solar hours with the twelve panels I have.
Thank you, hnymann
I may want to ask more as I put my system together
…And by the way …I believe I’m just around the corner …I’m in Floyd Co
Yes, we are close by, I’m in Jackson county. 
And if you have questions, ask away! There’s quite a few here with the experience to answer! 
I don’t know much about it,
….but I heard you guys talking about temperature affecting voltage maybe ?
…so knowing that you are in the same climate is helpful.
Yes, higher temperatures reduce solar output from the panels, and cooler temperatures will increase the output. It’s a helpful feature during the winter months when there’s less sun hours in a day, but the cooler temps helps the performance.
If it helps, here’s my post that gives some details about what I have set up, and that might give you some ideas. I have added updates for the current set up.
Thank you very much👍
I think my solar panel location is going to give me about a 200 foot run to my house.
Do you think I can still get away with 10 AWG?
Also I was noticing in your earlier post that I might need to use a breaker where the line goes into the house maybe?
And I saw that you had posted this one.
Otdorpatio Distribution Protection Box, IP65 Transparent Cover Electrical Box, ABS Power Supply Electronic Junction Box for Circuit Breaker Indoor on The Wall 5 Way, 4.72x6.30×3.74inch (120x160×95mm)
DC Miniature Circuit Breaker, 2 Pole 500V 20 Amp Isolator for Solar PV System, Thermal Magnetic Trip, DIN Rail Mount, Chtaixi DC Disconnect Switch C20
…I was wondering if that’s what I should do
…and I am assuming I need to put in a copper ground rod by the panel array and ground them
…do I need a fuse box anywhere …I would assume the breaker takes care of it
I’m really trying to understand every component since this is new to me
Sorry, I’m really unfamiliar with it all
I ran two sets of cables, one to each of my solar arrays, and then have them each directly connected to one of the MPPT solar inputs (ie: I don’t use the parallel mode). So one cable length is approximately 125 feet, and the other is 150 feet. I used 10 gauge wire for each, since there is a maximum of 12 amps on each set (limited by the AC300). I would go ahead and use one of the online DC voltage wire length calculators and see what voltage drop you get between 10 gauge and 8 gauge.
I did put in the DC breakers (these are different than AC breakers since DC can generate considerable arcing, and DC breakers have arc suppressors) so that I could disconnect the panels easily if needed, and for the current protection. They are good to have.
I do not have my panels grounded, although they are mounted on a steel support structure that is dug 4 feet into the ground. I do not assume that will ground them properly. There does not seem to be any agreement regarding what size solar array needs to have grounding, but clearly there would be no harm in doing it. We do use grounding rods for our solar-powered electric fence controllers though. For those we buy 6 foot copper ground rods from Tractor Supply, and believe me, my electric fences work GREAT! 
There’s a considerable learning curve to the whole solar panel use, that’s for sure!
Thanks again.
Yeah that’s the same way I’ve been using copper rods.
I’ve been using the 6 foot copper rods for ground on horse & goat electric fence’s also.