Just changed keyfob battery.
Battery type is CR2032
Simple to do.
Remove spare key from keyfob
Using a knife, carefully prise open the two halves of keyfob ( I worked around the casing until the 2 halves separated )
Please be careful at this stage, not a lot of pressure needed, you don't want to slip with knife and visit A&E.
The halves separate, one half holds the electronics and the other holds the battery.
Using the point of the knife prise the battery out of its compartment.
With the new battery, positive side facing downwards, push the side of the battery against the small spring in the compartment.
This allows the battery to drop into the compartment.
Once done take the half containing the electronics and align it with the bottom half with the battery and with a little bit of pressure press them together.
All done, just check the keyfob works, if it doesn't, have you put battery in wrong way/dud battery or even wrong battery.
The CR 2032 is very similar to the CR 2028.
Link video for nissan Altima (similar keyfob )
Faults and Technical chat for the Nissan Pulsar