I recently received PTO for my solar panel system. I am using “Backup” mode. On the first day of activity my 3 PW’s charged to 98%. They are slowly losing charge each day and are now down to 96%. Once they got to 98% all solar energy was directed to the home or the grid. Is this normal behavior? I expected them to charge to 100% and stay there until needed. Will they discharge to a certain level and then charge back up to 98%? Thanks.