Well, there's about 6 ICs and another 6 or 8 high powered diode or regulators on the internals of each battery. They are actually quite sophisticated. When DJI says they are intelligent, they mean it. What other brand tells you the exact voltage of each cell down to a hundredth of a volt, and how many times it's been charged, along with equalizing all 4 batteries in series without the extra equalization wires required on other drones? You even get to program each battery, telling it when to start discharging itself if accidentally left in storage too long, from 2 to 10 days to trigger discharging. Really cleaver stuff.
Take a look at the pictures below. This shows the internals, and what's in store if you decide to fabricate a multi-battery setup like others have been doing, hanging two more 1300mah batteries external on the P3 landing gear, or other means. By the way, it's not easy getting the top plastic cover off the battery, but if you work at it, it will pop off eventually, exposing the fat wires on the power connector. That's where you need to solder wires to route externally to other batteries, very carefully.
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