Yesterday was my first flying day of the year. I was able to test some new builds, some rebuilds, do a little 3D fixed wing, and put my recently acquired P2 and the new batteries through their paces.
In total I have three batteries, one I have done a full discharge to where the P2 assistant showed a terminal voltage of 9Volt (3Volt per cell) and 0% capacity. The remaining two batteries I charged to full capacity straight from the box.
First I flew the deep discharged and recharged battery. This provided around 20minutes of real world flight time (P2 carrying a Zenmuse H3-3D gimbal and GoPro). Next I flew the two batteries that I’d charged to full capacity out of the box. Both of the batteries went into auto land within a few minutes of take off.
Conclusion: Even though all three batteries were sold as new, and I have no reason to doubt that, I have no way of telling when they were manufactured or how long they sat on the sellers shelf. The built in balance and logic board was unable to determine the true capacity of the LiPo cells and suppose even after a full charge treated them as though they were still at a storage charge. Performing a deep discharge and recharge cycle, something DJI recommend every 20 or so uses, corrected this issue by recalibration the batteries internal circuitry.
So for other folk who still have a P2/P3 in their fleet but have not flown it for quite sometime, performing the deep discharge routine on the batteries may bring them back to life if you experience incredibly short flight times.