Infiniti FX35/FX45 key fob battery
Every model year listed for the Infiniti FX35/FX45 has a proven battery. The most common answer is CR1620. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 2003-2008Key-head remote
CR1620
FCC ID CWTWB1U751Two sites agree: uhs-hardware.com and americankeysupply.com (checked Nov 1, 2026)
Find CR1620 on Amazon - 2003-2006Remote (separate)
CR2025
FCC ID KBRASTU15Two sites agree: uhs-hardware.com and carandtruckremotes.com (checked Nov 1, 2026)
Find CR2025 on Amazon - 2005Smart key
Not confirmed yet
- 2007-2008Smart key
Not confirmed yet
Changing the battery
Key with remote in the head
- The remote electronics sit in the plastic head of the key itself, so there is no separate fob to open.
- Many key heads split along the side seam. Start at the small notch and pry a little at a time.
- The coin cell is usually under or on the back of a small board. Keep the rubber button pad in place while you swap the cell.
- Press the head together until it clicks and test the buttons. The transponder chip that lets the car start is separate from the battery, so starting should not change.
A CR1620 is 16 mm across and 2.0 mm thick. It is easy to confuse with the 20 mm CR20xx sizes, which will not fit.
Separate remote fob
- The remote is a small standalone unit. You will not need to touch the ignition key at all.
- Look for a screw on the back or a notch on the edge. Remove the screw if present, then twist a coin in the notch to split the case.
- Swap the cell or cells, keeping the same side up as the old ones.
- Reassemble and test from a short distance.
A CR2025 is 20 mm across and 2.5 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.
Keep spare coin cells away from small children. A swallowed coin cell can burn the throat within hours; if it happens, go to an emergency room at once.