What battery does a Toyota Avensis key take?

Toyota Avensis key battery

2009–2018

How to change a smart key battery

Slide the release catch and pull out the emergency key blade.
Wrap the tip of a small flat screwdriver in tape or a cloth, put it in the slot the blade leaves and twist gently to part the case. Keep it off the circuit board and contacts.
Note which way up the old cell sits before you lift it out. It varies by key, so don't assume + is up.
Fit a new CR1632 the same way up, holding it by the edges. Leave any grease on the contacts.
Clip the case back together and test the buttons at the car. Most keys work straight away with no reprogramming.
Keep new and old cells away from children. A swallowed button battery can cause serious injury within two hours.

2003–2008

Remote head keyCR2016
TransponderNo battery
A key with no buttons has no battery. It starts the car using a chip that needs no power.

How to change a remote head key battery

Look for a small screw or a slot along the seam of the plastic head. Undo the screw if there is one.
Wrap the tip of a small flat screwdriver in tape or a cloth, put it in the slot and twist gently to part the head. Keep it off the circuit board and contacts.
Note which way up the old cell sits before you lift it out. It varies by key, so don't assume + is up.
Fit a new CR2016 the same way up, holding it by the edges. Leave any grease on the contacts.
Clip the case back together and test the buttons at the car. Most keys work straight away with no reprogramming.
Keep new and old cells away from children. A swallowed button battery can cause serious injury within two hours.

Questions

3rd generation (2009–2018): CR1632 in the smart key. T25 (2003–2008): CR2016 in the remote head key.