I haven't timed it but it seems to take the same amount of time, I have over ten batteries and only one bag, which was sent to me with a battery. I used it once just to see and it was charged at the same time the one out of the bag was charged. Both batteries were down to %5.
Interesting. Well the heat has to go somewhere. I'll try a comparison test with an insulated vs. uninsulated battery and measure charge rate and battery temperature.