hitung aja minimal arus tiap servo, kalikan jumlah servo. siapkan baterai dengan kemampuan segitu.

calculate current each servo then multiply with number of servo. prepare enough battery.

Pretty much this; though you want to calculate using the "stall current" of the servo, not the "no load" current. This will give you the "worst case" scenario you are likely to encounter (that is, all servos activated, attempting to move, and can't), and is best to target for this if you can. Otherwise, in the case where the battery for the worst case is not feasible for the robot, then figure out how many servos may be running and potentially stalled at -any one moment-, and use that to figure out the amp-hour needs for the battery (so you can figure your run-time); note that amp-hours is not the same as amps!