Q. When is a charger really just a maintainer?

When the maximum current output of a charger is less than 1/20th the Ah of the total battery bank size it's trying to charge. It's effectively too small or too low a current to successfully charge a flat battery bank. The charger is now only able to maintain its state of charge. An example is the MXS 5.0 on an 70Ah battery is referred to as charging, but if you put that charger in motorcycle mode at only 0.8A it's now having a tough time maintaining the same battery.