This technology has been around for a few years now, most prominently in mobile phones.

The battery illustrated here (with a 7 cell 250mah NiCd above for comparison) is distributed by Perkins and they are, I believe, the first to be distributed widely by the modelling trade in the UK, available in 700mah and 1400mah forms. I bought mine from Channel 4 models. The batteries cost £15 each and the charger will cost you £15 - and yes, you must use a Li-Ion charger for these batteries!

The only other thing to watch is that they must not be discharged below about 2.6v per cell, i.e. 5.2v for these two cell batteries. A quick test using a GWS 2amp speed controller (with a NiCd battery!) showed that the auto cut-off operated substantially below this voltage so, either buy the speed controller that is sold especially for use with these cells, or take care! I have so far flown for 20 - 25mins without coming close to flattening a 700mah pack.

The figures in the table were measured using my Walrus as an example, and say it all really: More power, less weight and, most important of all, with two models equipped with these, you can fly all evening without having to take along charger or a 12v battery. The burning question now is, how long before this technology reaches the power tool market so we can use it in the big electric models!?