Lexus RX450H Manual page 549

4-3. Do-it-yourself maintenance
Replace the battery with a new one if it is discharged.

You will need the following items:
 Flathead screwdriver
 Small Phillips-head screwdriver
 Lithium battery (CR1632)

Replacing the battery
STEP 1
STEP 2
STEP 3
516
RX450h_EE
Take out the mechanical key.
Remove the cover.
Remove the battery cover
bolts and remove the battery
cover.