I have an S-A-A-2 unit. I used the unit for a while, then turned it off and plugged it into a USB charger. It took about an hour before all of the red LEDs under the unit were fully lit and not blinking, which I presume means it's fully charged.

I left the unit plugged in and set it aside and noticed a couple of days later that one of the red LEDs started blinking again, as if it's charging the battery. That lasted about an hour then all the red LEDs were lit again.

Now this morning it's doing the same thing. I'm not sure why it's starting a charge cycle every 12-24 hours nor why it takes an hour each time to charge the battery. The unit is shut off and just sitting on the table. I don't think it's discharging itself.

Has anyone else observed this? Should I unplug the charger as soon as the LEDs stop blinking? Why does it seem to always take an hour to charge, even after I've used it a while?