Help! Adding Different Volt Panels (24v) system

[Major90]

hi all,
i have a 24v current system with 4 305w 12v panels wired in series and 6 100ah 12v batteries wired in series. I have a 40a MMPT controller.

I want to add 3 to 4 more panels. The ones I'm looking at have a open voltage of 37.5, Omada 30.2, 245w. Can I just add this to the junction box leading to the controller and the controller will regulate it at 24 volts or do can this be paired in series also?

Thanks

[Mike90250]

Each string of panels, needs to have it's Vmp voltage be within 10% of each other. What happens is the lowest voltage string limits the voltage into the controller and you loose the the power the from the higher voltage string that is above the voltage of the lower string.
So if one string was 48VDC and the other string 28V DC, in parallel, the string voltage would be roughly about 28V and the high string of 48V misses out on supplying you power.

Your other problem, is your controller is only 40A. (MPPT controllers are rated in OUTPUT amps) Your existing panels, into a functioning MPPT controller, with good sun, would produce 50A. You are already slightly overpaneled, and adding more would likely drive your controller nuts. Some good ones, nothing bad happens. Less able controllers fry. 3 more panels would give you another 30A output, which is way over the limit.

So, i'd say, don't do it

( are you running a 12V system, 72V, or 24V - you mention 12V batteries, 6 in series and limiting to 24V. I'm guessing 24V )

[Major90]

yes its 24v. So what would you suggest. Getting another mmpt controller to handle the other panels?

[Mike90250]

Yes, to add more panels, you need another controller, your existing one is maxed out

[littleharbor]

Can you tell us what model your 305 watt 12 volt panels are. Never heard of such a large 12 volt panel. I have some Evergreen 205 watt 12 volt panels and, to be honest wouldn't want to have handle a panel 1/3 larger.