i saw in a tutorial, not an official dji tutorial, that each additional battery has to be updated with the firmware with the drone since they are intelligent batteries. so if i have three batteries i need to go through the update process three times? i don't see that stated in the manual for the batteries. is this true?

Yes, you would initailly upgrade the drone and the initial battery that is in it.  Then follow up with each additional battery.  If you don't you will get a message/promt "unmatached" firmware or something like that.

The batteries only need to be updated if the new firmware includes a battery firmware update. When updating the firmware on the drone, the battery that's in the drone will be updated at the same time (if needed). When inserting another battery that hasn't been updated, the DJI GO app will show an "Inconsistent Firmware Found" message like this if the battery needs to be updated. If you see that message, you should follow the instructions to update the battery. Those updates usually takes less than 60 seconds to install.

Hi there. Thanks for bringing this topic to us. Yes, you will need to update the firmware of each battery. Once you successfully update the firmware of the drone with the first battery, you can just refresh the firmware on the DJI Assistant 2 for the remaining battery so you don't need to repeat all the process from the start. Should you have further question, please let us know. Thanks for your support.

msinger's comment is key - note that 'The batteries only need to be updated if the new firmware includes a battery firmware update.' Not every update, actually a very small number of them, has a battery update. Don't get worried if you do an update and not prompted to update all your batteries.