Last year, I made the same rookie mistake and lost an airplane as well. I had a plane that had been sitting idle for about 5 months with an 1800mah NiMh in it. I plugged in the charger and in about 20 minutes the light started to blink, and I actually thought to myself, that was quick. I had about 1.5 before sunset and was rushing to get my flight in, so I just brushed it off. Well....4 times around the circuit, aileron control became erratic, 10 seconds later, tooth picks..... I knew it, I KNEW IT...I've seen this before with my Sirius charger on old (>5 year old) batteries and had to cycle them like 10-15 times before I was getting good rates. The moral of the story....Cycle those batteries at least once if you have not used them for a couple of months.

btw, I LOVE my Sirius charger best $250 investment I've made in the hobby, hands down.