Air New Zealand has updated the advisory for anyone traveling with lithium batteries.
You must let the airline know about any of these batteries when you book. Approval is usually given in the following circumstances:
Installed in electronic equipment in either carry-on or check-in baggage
Spare lithium ion batteries in carry-on baggage only, protected from damage and short circuit, limit of 2 per person
This means advising airlines when making the booking. So be sure to point this out to production staff who may be booking your flights.
(thanks to Murray Milne of the Techos' Guild for helping us to comprehend the rules)