Others have undoubtedly pointed this out elsewhere, but I wanted to note that the Lii-500 is a threat to cells when it’s not plugged in.
I needed a quick battery swap the other day while working with a headlamp and dropped a 14500 into my Lii-500 just before grabbing an AA from my collection of charged cells. I did not examine the display as the backlight came on as expected, but I had forgotten that the charger had been unplugged to make space for another charger. A few days then passed.
Tonight I found the 14500 sitting at perhaps 1V. The exact starting voltage is unclear as it began charging as a NiMH type after plugging in the charger, so the voltage quickly rose to ~2.3V before the Lii-500 lit the “End” symbol as it decided that charging was complete for a NiMH/NiCd type. It would not charge further as it understandably does not recognize this voltage as li-ion. I raised the voltage slowly via a dumb charger.
The Lii-500 has a “powerbank” feature that either has no low-voltage cutoff or continues its own quiescent drain even after cut-off. When inserting cells, it’s not immediately obvious that you have made this mistake unless you diligently check the screen to see that charging has started.
Yes, I have been diligent about this for years, but I missed it this one time and now I’ve damaged my only 14500. Nothing was pulling power from the Lii-500, but it has substantial quiescent drain when operating in powerbank mode; it will drain your cells while unattended.
The irony is that I’ve always wanted a discharge-and-stop feature on this charger and wound up building my own, but the Lii-500 sort of had this feature the whole time; it just doesn’t stop at 3V and instead goes to whatever minimum voltage keeps the powerbank running. It might be worth investigating whether the powerbank feature can be disabled altogether, but I doubt it.
This was an excellent charger for US$12-20 back in the day, but do not accidentally insert li-ion cells with the charger unplugged and then leave them there.