yes charging at 6 amps does heat the cells up but, you will get more punch with a higher charge amp, but when you charge at 5 amps it will not have as much punch, it might not be noticeable so my guess is that maybe you could charge them at 5 amps and see if you notice a difference but go from 5 to 6 because that will most likely show you the difference, and if you don't see any or feel any difference I would just charge them at 5 amps then I they stay cooler