Originally Posted by dkef
And no, my experience is that lithium batteries do not degrade significantly after a couple of years of inactivity. It might not be charged, but after a couple of charges it should be OK.
Quote from Wiki:
"A Standard (Cobalt) Li-ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively. In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge
So, it battery is full and is stored at room temperature, it has no capacity in 5 years, even if not used. To keep it in good health possibly requires it to store it half-charged and in refrigerator.
But, there is not only one type of Li-ion battery, but about 5+. The citation holds for standard one....
M92 is not comparable to cell-phone. Modern cell phone has to be charged every 1-5 days (depending if smart or not). M92 say every 2 weeks... Depends if WiFi is used... So it may be 25 charging cycles per year comparing to 360 cycles/yr for smarphone.