Mario's got a point, a 7ah sla has got to weight 1.5 possibly getting on for 2kg? a 2200mah 3s lipo would be more than enough for a 3 minute fight on two drills and a lifter, would weigh next to nothing and provide much more power than the sla could ever hope to. It would also take less space and like Mario said you could get two for the price of 1 sla.