Tools, Sharpening and Power Machinery - BEST Power screwdriver?

I have a 3.6 volt Black & Decker rechargable power screwdriver. I love everything about it except that it seems to lose its charge for no reason. I'll have charged it for days & it wont work for some season. I'll move it to a different spot to charge & it's fine. Then it doesnt work again. Perhaps, the rechargeable battery has a dead spot? I'd like to replace the whole screwdriver, but most of these things come in a huge kit & I dont need all the accesories. Im open to other brands: skil, dewalt, etc. I want something lightweight. Does the voltage have anything to do with the power? Any suggestions? Please advise. Thanks! Jina

I bought the DeWalt a few years back and have been very pleased with it.

I don't really have a preference, I have a Black and Decker a Craftsman, and a something or other I can't remember. They all work and have things I like and dislike about them. I think my next one will be one with a lithium ion battery - they sound like the hold a charge better, are smaller and more powerful - but also cost in the $30-60 range rather than the $10-45 range. As a casual homeowner use I'm looking at one from Skil but haven't convince myself I need a 4th power screw driver yet.

the new bosh LION are gettiing good reviews

http://www.amazon.com/Bosch-PS20-2-Litheon-Lithium-Batteries/dp/B000F4GITI/sr=1-1/qid=1165882376/ref=pd_bbs_1/102-0918347-1062507?ie=UTF8&s=hi