its not 'necessary' but it's extremely highly recommended if you're using anything smaller than a 1800mah battery and especially if you're using an 11.1v
as far as how long my battery lasts, a general rule of thumb is 1 BB/mah but it changes SO much and there are so many variables it's really impossible to give any sort of estimate.
My AEG got around 1200 rounds from a 1400mah lipo mostly semi auto
my PTW gets around 1.4bb/mah all semi-auto
and my 249 gets around 7BB/mah all full auto but it's specifically tuned to be maintain full auto very efficiently
You *could* run a 9.6v nimh stick, it probably fits in the stock tube, but a 7.4 lipo will last longer, much longer, and especially if you have a mosfet.
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