I have noticed something very odd in charging our two Sena Pi BT comms. Maybe someone else has noticed it too?

With all the concern about lithium ion battery fires, I have had a practice for several years that all of our battery chargers associated with our bicycles are run through a WiFi smart timer controlling the power to the outlet.  In this way, the power is automatically turns off after a few hours of charging. The smart timer is programmed to turn off the power after 7 hours, so every device has plenty of time to charge.  The timer controls power for all our bike-related chargers, including for the two Sena Pi, the rechargeable Trek bike lights, the Wahoo gps bike computer, and the Bosch powered e-bikes themselves. The purpose of the timer is safety. By turning the power off to the chargers we hope to avoid charging problems or a lithium ion battery fire. This approach has worked fine, except the Sena Pi appears to behave differently than any other rechargeable device we use.

I notice when the timer turns off the power to the chargers, the LED light on the Sena Pi stays on (lit in blue). There is no A/C power to the Sena Pi's charger, but the LED light is on. It must be using (that is, backfeeding power) from its internal battery to keep the LED lit. On every other device we charge, lights, e-bike batteries, whatever, the LED goes off when the power to the charge goes off.  

The problem is when we come back after a couple of days since our last bike ride. If we do not remember to unplug the charging cable from the Sena Pi, in only 2 or 3 days of non-use, the Sena Pi's battery is dead. It's like the blue LED runs the battery down after a couple of days. Very weird. Perhaps Sena's technical people can look at this issue and fix it with a firmware update.