Mixing panels wiring help. Growatt 24 volt

Ductgsxr

New Member
Joined
Aug 30, 2021
Messages
11
Location
Michigan
I have a 24-volt Growatt that I am replacing once the Eg4 6500 comes back in stock. But until then I want to connect an additional 4 250-watt solar panels to my existing 1200-watt (6x200) panels.

Here's the issue. The 250-watt panels are 37.4 VOC 8.3 Amps, and the 200-watt panels are 22.6 VOC 11.2 amps. The only way I see this working is 2s2p the 250 watts and get 74.4 Volts at 8.3 amps. Then 3s2p 200-watt panels at 67.8 volts at 22.4 amps. series both arrays together and that would leave about 135.6 volts (because it is the lowest voltage x2) and the amps should be 30 I believe. (All are used panels of about 5 years.)

2S2P 74.4 volts at 8.3 amps series to 67.8 volts at 22.4 amps = 135.6 volts at 30 amps. on 10 gauge solar wire 70 ft.

I plan on using a one-way diode on each positive series.

First is my math right, second is this safe? and third is there a better way of wiring them, or am I forced to use a second solar controller?

I would love to run the 4 250 panels all in series but that is 149.6 volts. and the Growatt is max PV input of 145 volts

Thanks for any help.
 

jpimlott

Solar Enthusiast
Joined
May 15, 2020
Messages
54
3s2p on the 200 watt and 2s2p on the 250 watts sounds good
As long the series voltage is close you use them and not lose much power
I have some 75 and 100 watt panel on the same series string no real issue
i also have a 72 cell in parallel with 60 cell. It is not perfect but loses a little because one of them is not at it peak tracking point
A 100 watt and a 200 watt panel in series would be a bigger lose as the 200 watt would only do 100 watts
In parallel they would be fine if they are the same voltage.
 

Ductgsxr

New Member
Joined
Aug 30, 2021
Messages
11
Location
Michigan
I wired it up that way and it's been working well, except I do have 3 panels that get shade so it brings all the panels down now. I ordered the new EG4 6500 ex which should be here this weekend per FedEx. That has 2 PV inputs up to 500Volts so that will fix my issue.

Thanks
 

jpimlott

Solar Enthusiast
Joined
May 15, 2020
Messages
54
if those panel are in one string then it should only be reduced by those panels
If those shaded panel are in different strings then they all are affected
 
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