Had I not walked in the room when I did, my house would have caught on fire. Since the fire would have begun upstairs where no one was, it would have most likely escalated to a large room fire or fully engulfed structure fire.
I have had the 4Sevens single bay charger for about three months. It has been used to charge AW brand (exclusively) 16340's, 14500's, and 18650's. I use the black cell, protected 3.7v lithium ion batteries with my 4Sevens lights and Zebralight SC600.
I was in and out of the room tonight while doing some chores, and had left my 2200 maH 18650 battery on charge. I keep a very close eye on the red/green LED light on the charger, and make sure I take the battery off charge as soon as the light turns green. I don't know if the charger has an auto off when it turns green, or if it continues to charge but I like to take the cell out as quick as possible to avoid over charge. With that being said, the selector slides on the face of the charger were set to the recommended setting for a 2200 maH 3.7v LiIon battery. The charge was set at 4.2v (the other option is 3.6v, used to charge 3v cells), and the other slide was set to 1A (vs 0.5A used for smaller capacity cells). These recommended settings are on 4Seven's web site. The battery was used previously in my Zebralight SC600 and I am certain that it had low life remaining.
As I walked in the room to get something, I could smell burning plastic. I took a quick look at the charger which had a red light indicating the cell was not fully charged, and what I saw was smoke pouring out of the positive end from an opening. The charger was quickly unplugged and taken out of the room. I actually burned my hand because the bottom was so hot. The plastic on the bottom side near the information sticker was soft and bubbled, I suspect there was a small fire inside or intense heat. Had I not unplugged it when I did, I think it would have caught fire within minutes.
What could have caused this? My guess is the circuit was goofed somewhere and the electricity was forced to circulate throughout the charger for a period, resulting in great heat build up. Any guesses?
I am very grateful I walked in the room when I did, otherwise the wall and carpet would have been on fire at least. The whole room or upper level of the house could have been on fire as well. I have read into lithium ion battery and charger dangers, as well as fire stories resulting from mishaps.