The max boost sign comes on when either an automatic (2 hrs based on a voltage drop below 12.3V) or manual boost (30 min) is initiated. It does not come off until the battery voltage has risen to the boost maximum of 14.4V, and is able to hold this for the specified period of time for the boost program that has been initiated.
If, for some reason, the full boost charge time cannot be completed while PV current is available, the remaining time is added to the next day’s boost schedule.
So, for example, if the user initiates a manual boost at the end of the day, and there’s not enough juice to get the battery up to 14.4V before the sun goes down, the 30 minute boost time is added to the next day’s “automatic” boost cycle when PV current is available again. So, instead of a 2 hour boost cycle, the next day the battery will boost for 2.5 hours
Now, the boost memory can be cleared if the user makes a “hard reset” of the controller. However, if the battery is below 12.3V when reset, the boost symbol will stay on because the controller detected a battery voltage below the boost activation voltage.
So, the first thing to check is what the battery voltage is at when restarting the controller. It’s a good idea to verify this with a multi-meter both at the controller terminals and directly at the battery in the event there is a voltage drop in the wires.