I would say it's the j or i part that make the use of battery and not C or D bins, big power battery will not sag to much, were as some li-ion when pushed near there limit of voltage and discharge rate do, i use a J bin as DD and a I bin using Der Wichtel driver, i have it turned down to 3.25v at 2.3amps takes about 0.79 amps across the tail to battery well with in most batterys discharge limit, but with DD i can see 3 amps across the tail which can some times over tax the discharge rate, this only last for a very short time due to the loss of forward volts say 4.15 drops quickley down to 3.6 ish, hope i,ve got this right good luck DocD