Originally posted by AstroDave It might recover if you leave it on the charger long enough. When I was doing battery testing, I (inadvertently!) let a battery completely discharge. I feared it might be kaput, but after 10-20 minutes on the charger, the green charging light came on and the battery seems to have fully recovered. Certainly worth a try to save a $50 battery!
We had this discussion recently.
When a Li-Ion is completly discharged, it NEVER EVER can be recovered!
That's a law nobody can change.
But .... if you leave your Pentax switched on and you don't use Auto-Power-Off, then it will still switch off before the Li-Ion is fully depleted. Thats why it went o.k. afterwards. Kind of a security buffer sensibly installed into most Pentax. Can't remember how it was for those with AA's, hardly used them except *ist-DS.