Growatt 24v 3kw for beginner

[Eloha7]

I am building a solar system with the Growatt 24v 3kw.

I want to use the maximum capacity of the Growatt and put 5 panels of 400w.
If I understand well I have to put 2 in series and 3 in parallel.

I will start with 2 SOC 12v 100AH batteries. I think 4 would be ideal.

However, I wonder if I don't have enough battery power, how this will affect my energy input into the house if there is a complete power cut.
In other words, if I am off-grid, is the energy from my panels reduced by my batteries or does the energy go directly into the house?
I hope it's clear????
Thanks

 

[MisterSandals]

5 panels of 400w.
If I understand well I have to put 2 in series and 3 in parallel.

2 in series and 3 in parallel is 6 panels.

 

[MisterSandals]

.

In other words, if I am off-grid, is the energy from my panels reduced by my batteries or does the energy go directly into the house?

It will simplify your thinking if you assume all the energy from the panels goes into the batteries. And, the inverter in the Growatt takes the energy stored in the batteries, converts it to AC and makes it available for use "in the house".

I will start with 2 SOC 12v 100AH batteries. I think 4 would be ideal.

Have you done an energy audit to see how much energy you use in a day and how much of that needs to be stored in the batteries outside of the solar harvesting hours?

 

[Eloha7]

2 in series and 3 in parallel is 6 panel

2 in series and 3 in parallel is 6 panels.

View attachment 32892

.

It will simplify your thinking if you assume all the energy from the panels goes into the batteries. And, the inverter in the Growatt takes the energy stored in the batteries, converts it to AC and makes it available for use "in the house".


Have you done an energy audit to see how much energy you use in a day and how much of that needs to be stored in the batteries outside of the solar harvesting hours?

Ok, so how do I connect my 5 panels?

I use an average of 400kw/month. So per day is 13.3kw. Divided by 7.2 hours of sun divided of 0.9 efficacity = 2.05kw So I need 5 panels of 400w.
For the batteries I am not sure. I have been on differents ''battery calculator'' on internet and it confused me a little bit. I think I use around 50% of my consumption during night time. I can pu my fridge on a timer during night time. Maybe I can reduce it to 40-30% using only minimal led light.
Thank you

 

[MichaelK]

I think what the OP is trying to say is that two of the panels would be wired in series, and then the other three just in parallel, which would be 2S+1P+1P+1P.

Elonha, that absolutely can NOT be done. All parallel connections must have identical, or almost identical voltages. Your choices are 1S5P, or 2S2P, or 5S1P. Assuming that one of your panels has a Voc of ~45VDC, then 5 in series would be 225V. What's the maximal voltage your inverter is rated for?

For the proper charging of a lead-acid battery, you want about 1/8C as the charging current. The math would work out to be...
100Ah X 0.125C X 26V charging X 1.25 loss compensation = 406W

I could not find a reference to a SOC battery? Is it lead-acid, AGM, or Li? The respective charging rate for each type is 0.125C, 0.2C, and 0.5C respectively. Depending on your battery type, just one or two panels is about what you would want.

Now, getting back to the size of your batteries, you have 100Ah X 24V = 2400Wh of power, or 2.0 kWh. Assuming you use only half the capacity of a lead battery, that 1000Wh. No way that would power the whole house more than a single night. It might keep the lights on, and maybe the frig if you keep the door closed, but this size battery will be totally depleted in grid-down situation. For whole-house power, you really need to look at 400-500Ah for a viable system.

 

[Eloha7]

The VOC maximum is 145. So I cannot put 5 panels of 400w? So the only way to get as close as possible of the maximum 2000w will be to have 6 panels of 325w? And connect them as MisterSandals show in the picture?
The Soc batterie are lithium.
The idea for the batteries is to buy 2 (limited budget) and to get 2 more later.

 

[Fallingaway]

145 on the panels or growatt? As long as a single panel does not go over the voltage limit of the growatt you can use the 400W panels. Hooking them up in series will double the voc of the panel, parallel will double the amps. It’s really important you know these things before you start booking it up. Go over voltage into your growatt and your gonna fry it. I would try and stay 10-20% under the maximum voltage of the growatt to be safe.

 

[Fallingaway]

Not to be an ass but, as another person on a budget and trying to make a build, it absolutely kills me when I hear others buying gear first and then trying to figure out if and how to hook it up! You should 100% know BEFORE you start making purchases on your “budget” build if the damn components are even going to work together.

 

[schmism]

Your going to want to run a 2S config. so 4 total panels or 6. 24v growatt has a 30-145v MPPT. Its a 80a MPPT so the 24v should support ~2000w of solar

 

[MisterSandals]

Hooking them up in series will double the voc of the panel, parallel will double the amps.

No!

The 5 panels when in series will be 5x the Voc of 1 panel.
The 5 panels in parallel will be 5x the amps of 1 panel.

 

[Fallingaway]

5 in series isnt an option for the OP. He can do 2 at best with his growatt, which is why I said double the PANEL, not PANELS. Instead of trying to be the smartest person on the forum, perhaps you should follow along with the actual question and try to help that way.

 

[MisterSandals]

Instead of trying to be the smartest person on the forum, perhaps you should follow along with the actual question and try to help that way.

Words have meaning and saying that connecting panels in series doubles the voltage is misleading at best if the OP had only 2 panels.
The OP actually has 5 panels and from what i can tell, it has not been determine how they can be wired yet.

 

[Fallingaway]

They do have meaning, panel is singular. Panel(s) is plural or meaning more more than one. At no time was more than two panels even suggested as an option available for the situation. This is why I used the word panel in the singular format and said double, both of which were appropriate use of grammar if your following along with the conversation.

 

[MisterSandals]

So the only way to get as close as possible of the maximum 2000w will be to have 6 panels of 325w?

Yes, with your panels and SCC, you are limited to an even number of panels. If you can get a 6th panel you can use the 5 that you already have. It would be ideal if you could get an identical 6th panel; at the very least, the Voc and Isc should be close.

4x 325w = 1300w
1300w / 28v (charge voltage) = 46a (as schism said, supported and handled by an 80a charger, but batteries?)

6x 325w = 1950w
1950w / 28v = 69.6a (also handled by an 80a charger, but batteries?)

Is it lead-acid, AGM, or Li? The respective charging rate for each type is 0.125C, 0.2C, and 0.5C respectively.

This is REALLY important in regards to how much charge current your batteries will handle.

 

[Hendo7]

hate to butt in ,but i have the same growatt and i am a little confused about how many panels i can hook up to it, as far as i have learned from this thread i can hook up 8 x250 watts panels but the growatt says 145 volts max my 250 watt panels are open voltage of 30v does that mean i will be over the voltage ? of 240 volts

 

[Bud Martin]

hate to butt in ,but i have the same growatt and i am a little confused about how many panels i can hook up to it, as far as i have learned from this thread i can hook up 8 x250 watts panels but the growatt says 145 volts max my 250 watt panels are open voltage of 30v does that mean i will be over the voltage ? of 240 volts

You will setup the panels as 4s2p.
4 panels in series will give you total Voc of 120V, 120V *1.2 for low temperature compensation = 144V which is still under 145V max PV input.

 

[MichaelK]

hate to butt in ,but i have the same growatt and i am a little confused about how many panels i can hook up to it, as far as i have learned from this thread i can hook up 8 x250 watts panels but the growatt says 145 volts max my 250 watt panels are open voltage of 30v does that mean i will be over the voltage ? of 240 volts

You are thinking of a single string of 8 panels, identified in shorthand as 8S1P. That would give you about 8A at 240V. That is only 1 way they could be wired. Two other alteratives would be either 4S2P, or 2S4P. 4S2P is two parallel strings of four panels each producing 8A at 120VDC. So, 4S2P produces 16A at 120VDC. The second alternative, 2S4P would be four parallel strings of 2 panels each in series. That would give you 32A at 60V.

To properly wire your inverter, you need to know both it's maximal voltage, and also it's maximal amperage.

The last possible option would be 1S8P, but 30V might not be enough to charge a 24V battery.

 

[Hendo7]

thank you very much Bud Martin

 

[Hendo7]

thanks to michaelK

 

[Fallingaway]

I get that this is a place to ask for help and it’s a great place for sure but, I can’t wrap my head around why people are buying growatts and panels etc and don’t first understand the basics like serial and parallel. Do people not make a plan anymore first before dropping hundreds or thousands of dollars on equipment first?