The latest gen Bosch 12 v batteries are 2.5AH, paired with the ps32, the brushless drill, you could go all day. Save a little and get the ps31- non-brushless, and it ought to be more than enough for what you describe, and power wise were a pretty significant improvement over the first version that MRVM spoke of. The newer impacts, ps41, is definitely suitable for tasks such as deck building, mine didn't balk at 1/4" lags in treated pine.
I have several Bosch 12 v and looking to get the heated jacket soon, they're all great compact, comfortable tools with a good power to size ratio. The only ones I would stay away from are the right angle drill, and the OMT. It's a great line, a step down from M12 in both power and size, but not in quality in my opinion.
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