my SMC 4200 packs charge to 4550, i run than let them sit discharge than i charge for 500 sec till the next week, than i discharge than charge at 6A than run, if you dont put 500 to 600 sec of charge back in the pack the pack will die,and if you are gona let them sit for longer than a week than fully charge them. the 4200 cells discharge so fast and the IR is so low 1.4 to 1.1.