As a rule of thumb, around 10% either way can be had with little change in the effect. Most households in the US and Canada don't have a perfect 110v system anyways. My house for instance was build ~40 years ago and uses an older, different wiring standard, and as such we get about 104-105v. Doesn't make too much of a difference. The charger system acts as a transformer to step down the voltage and then provide steady current at a rate of 300 mAh. The end result from starting with a higher voltage before stepping it down is that it will carge at a ever so slightly higher mAh. Its a 200mAh battery on my AEP and it charges in about 40 min, just like its supposed to.
The final answer is than I and many others have had AEPs for months with no major disasters, and even the retailers say its ok:
http://redwolfairsoft.com/redwolf/pr...p?prodID=16773