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I need help with solar system

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Danny1987

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Feb 19, 2022
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I need help with solar setup. So far, I have purchased (4) 300ah 12volt batteries, a shunt, a Growatt 12k inverter from signature solar, and (25) 430W panels. I’m missing breakers, fuses and wires/cables and have no idea what sizes would be required if the inverter was to be utilized to close to it's full potential. Most likely won't be.

My current location is space limited so only 4 panels will be utilized, this is for testing purposes mostly. Full install will be done in a different location sometime this summer. Thank you everyone in advance for your help.

1. What wire gauge? At the most the distance will be 100 feet from panels to inverter.

2. Breaker or Fuse size? if it were a full 24 panel array. Any suggestions which ones to purchase.

3. AC load wires gauge? Are these the cables running into a sub panel? The panel would be next to the inverter.

4. Since this is a 250VDC inverter would five 48v panels in series still work? if it were right at or just under 250volts? Can a device be used to limit the voltage or few parallel strings be necessary for the full array?

5. Battery jumper cable gauge? Any fuses or breakers needed?

Am I missing anything?
 

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Going off your drawing.
Put a 15 amp fuse in a mc4 fuse holder between your positive wire and the first panel.
12 awg for solar power wires.
Also recommend a solar disconnect near inverter for maintenance purposes.
200 or 300 amp class T fuse on positive battery wire, close to battery.
And a battery disconnect switch.
Ac wiring size and breakers according to inverter instructions.
 
timselectric said:
Going off your drawing.
Put a 15 amp fuse in a mc4 fuse holder between your positive wire and the first panel.
12 awg for solar power wires.
Also recommend a solar disconnect near inverter for maintenance purposes.
200 or 300 amp class T fuse on positive battery wire, close to battery.
And a battery disconnect switch.
Ac wiring size and breakers according to inverter instructions.
Click to expand...
Just ordered all the above except T class fuse. Between 200 and 300 amp, would one be better than the other?
What should the battery jumper cable gauge be?
Thanks
 
growatt 12K takes up to 250v PV input. 430w pannels are likely in the 40v range. so 5 in series? You have 25 pannels so 5s5p. The growatt also has 2x SCC inputs so you'll need to split that 5s5p into 2 groups. 3p MC4 combiners exist however they are not rated for 30a. Id be useing a combiner box. The one i use for my dual SCC is a midnite solar MNPV12. If you wanted a more ballanced PV you can do 2x 4s3p (each side) and not use a pannel. (keep in reserve if something happens to one of them)
30amp home run is #10 or #8 depending on wire run.

Some napkin math on your battery size compared to the total system. Expect the battery to only run a 700-800w load continuous "overnight" any more than that and your going to run out of battery before the sun comes up. however once it does, it will be recharged in something like 2 hrs.
 
A 12kW inverter on 48V can pull up to 12000W / 48V / 0.85 = 300A.

Your batteries have a max continuous discharge current of 200A. This means you can only use 8000W of your 12000W inverter. If you want to take full advantage of the inverter at times you should buy two or three 48V batteries and put them in parallel instead of buying large 12V batteries to be put in series.
 
That inverter can provide up to 120A of charge current.

Your batteries state a standard charge current of 60A though they seem to state a max of 120A. So again, you are better off putting 48V batteries in parallel.
 
schmism said:
growatt 12K takes up to 250v PV input. 430w pannels are likely in the 40v range. so 5 in series? You have 25 pannels so 5s5p. The growatt also has 2x SCC inputs so you'll need to split that 5s5p into 2 groups. 3p MC4 combiners exist however they are not rated for 30a. Id be useing a combiner box. The one i use for my dual SCC is a midnite solar MNPV12. If you wanted a more ballanced PV you can do 2x 4s3p (each side) and not use a pannel. (keep in reserve if something happens to one of them)
30amp home run is #10 or #8 depending on wire run.

Some napkin math on your battery size compared to the total system. Expect the battery to only run a 700-800w load continuous "overnight" any more than that and your going to run out of battery before the sun comes up. however once it does, it will be recharged in something like 2 hrs.
Click to expand...
Thank you for the detailed post. I agree 100% with the battery assessment. I plan on purchasing another (4) batteries as these are 300Ah and per the manual Growatt requires 400Ah.
Would using 300Ah battery bank damage the inverter or battery bank possibly?
Is there a way to wire up 6 or 8 12V 300Ah batteries to stay within 48V and be above 400Ah or would I need to purchase another battery bank all together?
 
Danny1987 said:
Is there a way to wire up 6 or 8 12V 300Ah batteries to stay within 48V and be above 400Ah or would I need to purchase another battery bank all together?
Click to expand...
You can wire 8 12V 300Ah batteries in 4S2P. This will give you a 48V 600Ah battery bank.

Though you really should consider returning the 4 batteries you have and look into getting 48V batteries that you can put in parallel. There's a lot less to worry about. Putting batteries in series is more wiring and you have to worry about keeping them in balance. 48V server rack batteries seem to be popular and reasonably priced. Will has done several videos on them lately.
 
Again thanks everyone for the advice. Just spoke to Amazon and they've accepted the battery return.
Any suggestions on which 48v server rack batteries to buy? or any battery that would be capable of continuous discharge rate of at least 11-10kw?
 
See Will's page on 48V server rack batteries:

www.mobile-solarpower.com

Server Rack LiFePO4 Solar Batteries

High quality, high capacity solar batteries at a great price! These are taking over the market because they have everything. State of charge indicator, communication system, high quality BMS and a...
www.mobile-solarpower.com

In order to make full use of your 12kW inverter you need a battery bank that can support 300A or more of continuous discharge current. Batteries in parallel can split that load. So if you buy a 48V battery that supports 100A discharge current then you need 3 or more in parallel. If you get one that supports 150A then you need two or more in parallel. So pick a combination that gives you the desired total capacity (Ah) and sufficient continuous discharge current.
 
rmaddy said:
See Will's page on 48V server rack batteries:

www.mobile-solarpower.com

Server Rack LiFePO4 Solar Batteries

High quality, high capacity solar batteries at a great price! These are taking over the market because they have everything. State of charge indicator, communication system, high quality BMS and a...
www.mobile-solarpower.com

In order to make full use of your 12kW inverter you need a battery bank that can support 300A or more of continuous discharge current. Batteries in parallel can split that load. So if you buy a 48V battery that supports 100A discharge current then you need 3 or more in parallel. If you get one that supports 150A then you need two or more in parallel. So pick a combination that gives you the desired total capacity (Ah) and sufficient continuous discharge current.
Click to expand...
This really makes things easy to understand.
I found these EG4 48V 100AH lifepower4 battery 48V/100AH 5.12kwh from signaturesolar. Would post a link but not sure if allowed.

And just to be certain, 4 of these EG4's connected in parallel would allow for 12k draw or close to it?

Edit: Just realized those are the server racks from Will's post*
 
Danny1987 said:
Would post a link but not sure if allowed.
Click to expand...
Links are allowed as long as they are not affiliate links.

Danny1987 said:
And just to be certain, 4 of these EG4's connected in parallel would allow for 12k draw or close to it?
Click to expand...
4 in parallel gives you 400A of discharge current so that supports the 12kW inverter. And you will also get 400Ah of capacity.
 
Sorry if I'm repeating myself. But with these (4) EG4's in parallel, is a 300 amp fuse appropriate in this setup for the possible 12k draw?
Edit: class T
 
With a 300A draw you need a 375A fuse which means a 400A fuse since you won’t find 375A.
 
rmaddy said:
With a 300A draw you need a 375A fuse which means a 400A fuse since you won’t find 375A.
Click to expand...

Are class T fuses rated for exact/specific voltage, because this one on Amazon is rated at 400A but the product description only mentions 12 and 24 volts no information whether it would work on a 48 volt system.

Can this one be used?
 
That’s one downside to 48V. Your batteries are more like 58V and it can be hard to find switches and fuses rated for 58VDC.
 
Fuses are like wires. If you flow too much current through them, they will melt. Breakers and switches on the other hand. Have to open the circuit and extinguish the ark. In a manner that doesn't create any damage to the device. So that it can be used over and over. A fuse is a one time use device.
 
I really appreciate all the help guys. I'll be skipping Amazon's 12/24v.
Turns out Walmart.com and invertersupply.com sell the exact same model as Amazon. All the same price. But slightly different parameters on exact same models numbers.

But Walmart's product page claims up to 160VDC. Is this the correct voltage number I am looking at?
  • Includes insulated polyester reinforced polycarbonate base mounting block, fuse, and protective cover
  • Lightweight, quality design
  • Extra heavy duty DC-rated fuses with slow blow functionality
  • 18-8 stainless steel, 5/16 fastenings
  • Fits all fuses and the wiring range is #6 to 4/0
  • Protects inverter
  • For RVs, boats, cars and trucks
  • DC rating: 160 VDC
  • Interrupt rating: 50,000 amperes
Invertersupply:
The Class-T fuses range from 110 to 400 amps. One block size fits all fuses and the wiring range is #6 to 4/0. Go Power! Inverter Fuse Blocks operate on all 12, 24, 32, or 48 volt inverter battery systems.

and Amazon just 12/24. Of the two, I'm leaning towards Walmart's because of the 160VDC rating. Or am I wrong?
 
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