That is strange, I have been using Li-ion for a while without any problem. In fact, I have the heli lift off higher and longer than the stock NiMh battery. I am using 2 cells Li-ion weight in at 78 g (or 2.8 oz). I tie it to the frame right under the receiver and the CG is right on - No more adjusting the CG everytime I change the battery as in the stock LiMh battery. If you search the article on battery on the internet, you will find Li-ion has LESS internal resistance than Li-Ploymer - ie. higher current output. Li-ion has most of the advantage over Li-polymer except the little bit heavier than Li-polymer (due to the metal casing of the Li-ion). Internally, they build differently but it doesn't affect the way I use it. They both use the same charging method.