If you have more than one saber or device that takes higher voltage batteries then I'd recommend picking up a Nitecore D2 or D4 charger. It's not very expensive, and automatically recognises just about any battery you can throw at it, charges it to perfection, and has a great meter telling you how it's doing.
I have a few torches and sabers that take 18650's and other exotic batteries, and wouldn't be without one of these to look after them.