The versions we have out there now are good for Rasperry Pi Zeros, A+, 3B+ but a little marginal for 4B implmentations. We are in design for using SolarMAX for the Raspberry Pi 4B. It took us quite a while to figure out what was going on with some systems but not with others!
I'd expect a SolarMAX for 4B to be released 1Q (yes, it works in the lab now but we have to gather some more information on how these Lead Acid batteries behave with our charger to configure the software.)
Here is a shot of our test setup running a Raspberry Pi 4B running SkyWeather2. This shows a whole charging cycle from a deeply discharged battery. We think this is what our software was screwing up by thinking the battery was changed when it was in trickle mode (how you recover a deeply discharged Lead Acid battery). Watch www.switchdoc.com for updates.