Dual Controller

Fede

Current Installation - 4ea Solar Panel banks composed of 3ea Solar Panels in series (270w/38v/10a ea). One MPPT 150/60 controller and 3ea 24v battery banks composed of 4ea 6v 240ah flooded batteries. Banks are connected in parallel, so the controller input is a little over 40a @ 104v. Thinking about adding a second controller in order to separate the panel banks (Two banks per controller) so I can get higher amperage into the battery banks. My controller's maximum output is 60a so If I divide my panel banks with a 2nd controller I estimate amperage will go up closer to 90a. Still in doubt if this much amperage will make any difference in charging time since my controller voltage output will remain at 27v.

Estragon

Adding a second controller makes sense for a couple of reasons:

First, the four strings of panels might reasonably produce 270 x 12 x 75% /24 = ~100a, well over what a 60a controller will use. The flooded batteries, 3 strings x 240ah = 720ah should be able to accept bulk charge at about that 100a rate.   A second 60a controller would give you 120a capacity, allowing for better use of pv.

Second, one controller running flat out at 60a in bulk will get hot, and reduce life expectancy.

The extra current for battery charging will be available for bulk charging (eg 50% SOC ~24.2v to 80% ~ 29ish volt absorb).  Having the extra current available should shorten this bulk stage.

mcgivor

An additional charge controller would definitely make sense to maximize potential whilst minimizing stress on the electronics. When a controller is run close to maximum capacity it will produce heat. The Schneider 60-150 MPPT for example, which is passively cooled, will begin to reduce its output when the heatsink reaches 45°C. During hot days >34°C ambient the heatsink will reach 60°C + under 40A charging current, if 60A were available the output would still be ~40A. With an auxillary fan creating airflow the heatsink temperature remains at ~36°C. Being that in my case these ambient temperatures are the norm, I've not had the opportunity to test under cooler ambient conditions say around 20°C.