Hello-    I recently purchased 2 new Batteries on Ebay for my Phantom 3 Advanced.   Please keep in mind these are original DJI batteries.    I have heard that I should do nothing and my tablet will tell me during start up if I need to do any type of updating.   Is this correct?   I also been told that I should do some type of update as soon as I get them. Is this correct?  I don't even know how to update these batteries and if I need to even worry about it..  HELP !

The DJI app will tell you if the batteries require update. Just be sure to fully charge them before flying.

Updating the battery is also same as updating the firmware . When you do firmware update the battery, esc and imu are also updated . Simply to say all you need to do if you've already done updating the drone before and the bin file is still in the sd card all you need to do is connect the new battery and do upgrade will be initiated automatically

Above posts are correct, if anything needs updating (aircraft, RC, batteries) the app status page will let you know.