Solar Newbie Sanity Check

EL_Kab0ng

New Member
Joined
Oct 13, 2021
Messages
2
Hi, everyone!

As the title says, I'm a solar newbie and have started to gather the parts and pieces I need to have an off-grid solar powered gym at my home. I have watched and watched countless hours of Will's videos taking notes to make sure that I have exactly what I need. Over the last week, I started buying the components and-naturally-have started second guessing my knowledge base and purchases. I have searched the forums and found some useful information, but essentially, I just wanted to see if I could get a sanity check on what I've compiled to know if I'll be good to go, or will fry everything when I go to set it up later this month.

What I'm trying to power:
196sqft building with no grid power
Midea U Inverter 8,000 BTU Window AC (710W Cooling, 8.78A Cooling) - will run at least 4-5 hours a day on Cooling mode
A 55" LED TV - Will be on no more than 3 hours a day.
Two iPhone Chargers

What I've purchased:
1 x Growatt 24V SPF 3000TL LVM – 3kW
8 x SanTan Solar T Series 240W (I think I over did it with the panel purchase)
1 x 8-1 Solar Panel Combiner Box - 1 x 125A Output
1 x Battle Born BB5024 battery

Originally, I wanted to have a 2kw (8 panels, 30.4 VMP) array on my roof that would run the AC and pretty much anything else I wanted, without issue. So, that's what I bought. Somehow, I think I missed the part where the Inverter was limited to specific voltage. From what I've read, the Growatt is limited to 145 Volts, while my purchased array would be 243.2 Volts (VMP). If my thinking is correct--that I've over purchased panels--the math indicates that I can only have 4 panels connected to this Inverter, pulling me down to 121 Volts VMP.

Can anyone check me on this? Like I said, I'm a total newb and don't want to blow up any of my new stuff the minute I plug it all in.

Thanks for all the help!

~Carlos
 

Porch

Solar Addict
Joined
Jan 17, 2021
Messages
267
You will want to series and parallel the panels. So 3 panels connected in series, then wires to your combiner/breaker box. Then another 3 panels in series, wires to the combiner box. You want to wire them in sets of 3 so the combined voltage of one series set does not go over 145v.
 

rmaddy

Full-time Solar-powered Trailer Life
Joined
Nov 16, 2019
Messages
1,734
Location
USA
It's the panel Voc, not Vmpp, that you need to worry about with regard to the charge controller's max voltage input. Those panels are rated at 37.2Voc. If the max is 145V then you are limited to 3 in series. Voc goes up in the cold so 3 panels could reach up to about 130V on a really cold day. But that assumes the panels are new and they are angled ideally for the sun.

You could buy a 9th panel and go 3S3P. Or stick to the eight and go 2S4P. Once you get to 3P or more you need a combiner box and fuses which you have.

Do keep in mind that your battery is 24V 50Ah = 1200Wh. Your A/C is 710W. Your battery will be 100% drained after 1 2/3 hours if there's no sun providing any solar. Add in the other items and the inverter inefficiencies and you might get 1 1/4 hours or less on a rainy day.
 

EL_Kab0ng

New Member
Joined
Oct 13, 2021
Messages
2
Thanks for the replies @rmaddy and @Porch. Stupidly, I didn't even think about the battery wattage for some reason (I think I got hung up on the volts), so I'll see how the system works when it's pieced together and see what my needs are. Or maybe I'll just buy another battery or two while they're on sale... who knows.

Also, as for the 2S4P setup, I think that's the route I'm going to go since the area of the roof can only accommodate 8 panels, 9 would create an overhang situation that I want no part of. I found a diagram on a different post on the forums (here) and I'm wondering if I need the 4:1 MC4 connectors or if those 4 pairs of cables would just go directly into my combiner box?

Here's the diagram from @wtrey613.
1625863313279-png.55604


~Carlos
 

wtrey613

New Member
Joined
Jan 15, 2021
Messages
41
Thanks for the replies @rmaddy and @Porch. Stupidly, I didn't even think about the battery wattage for some reason (I think I got hung up on the volts), so I'll see how the system works when it's pieced together and see what my needs are. Or maybe I'll just buy another battery or two while they're on sale... who knows.

Also, as for the 2S4P setup, I think that's the route I'm going to go since the area of the roof can only accommodate 8 panels, 9 would create an overhang situation that I want no part of. I found a diagram on a different post on the forums (here) and I'm wondering if I need the 4:1 MC4 connectors or if those 4 pairs of cables would just go directly into my combiner box?

Here's the diagram from @wtrey613.
1625863313279-png.55604


~Carlos
Just an FYI. I had to go FROM 2SP4 to 4S2P because the min input voltage on my growatt ES5000 is 120Volts!!
 
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