I hate to sound like I work for DeWalt or something here, but this is what I think. With the 36v DeWalt batteries, they use "nano" technology. It's a phosphate lithium ion that they claim won't lose power when it's just sitting. When I bought mine, I charged up the batteries, used it once, and then packed it in the closet. It was about 6 months until I got it out again. I thought that I would have to charge the battery, so I plugged it in, and right away the light indicated that it was fully charged. I've used that gun a bunch, and haven't charged the battery again since. The only problem is that they are pretty expensive, but they are convienient. Not trying to sway you one way or the other, just giving you my observation.