When I added 2,000 taps in 2013, I thought that the 18v Milwaukee drill that I had with 5 Lithium ion batteries ( 3- 2 amp hr small xc and 2 - 3 amp hr large) and would work fine to do a days worth of taping. I got about 125 2" deep 5/16 holes with each of the 3 amp hr larger batteries and 35 - 40 holes with the small 2 amp hr batteries. All 5 batteries were dead by 1:30. I went home, researched Dewalt drills and bought the 20v max xr brushless drill (DCD 995) with 2- 4 amp hr batteries. The drill is a bit heavier but has a 2,000 rpm speed. The batteries consistently get 325 -330 holes from each battery. On a good day, I can sometimes put in more than 650 holes, so I bought a third battery and that one does 410 holes. (I checked it twice, 414 the first time, 410 the second use). My opinion, Dewalt all the way.
2004- 470 taps on gravity and buckets
2006- 590 taps on gravity and buckets 300 gph RO
2009- 845 taps on vacuum no buckets, 600 gph RO
2010- 925 taps on vacuum new 2 stage vacuum pump
2014- 3045 taps on vacuum, new 1200 gph RO
2015- 3104 taps on vacuum
2017- 3213 taps on vacuum
3' x 10' oil fired evaporator with steamaway