Mazda RX-8 key fob battery
4 of the 8 model years listed for the Mazda RX-8 have a proven battery. The most common answer is CR2025. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 2004-2005Remote (separate)
Not confirmed yet
- 2006Remote/transmitter (keyless entry, form not stated)
CR1620
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “CR1620 or equivalent”
Find CR1620 on Amazon - 2006Smart key (advanced key)
CR2025
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “Replace only with the same type battery (CR2025 or equivalent).”
Find CR2025 on Amazon - 2007Smart key (advanced key)
CR2025
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “Replace only with the same type battery (CR2025 or equivalent).”
Find CR2025 on Amazon - 2008Remote (separate)
Not confirmed yet
- 2009Remote/transmitter key (form not stated)
CR1620
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “CR1620 or equivalent”
Find CR1620 on Amazon - 2009Smart key (advanced key)
CR2025
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “Replace only with the same type battery (CR2025 or equivalent).”
Find CR2025 on Amazon - 2010Remote/transmitter key (form not stated)
CR1620
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “CR1620 or equivalent”
Find CR1620 on Amazon - 2010Smart key (advanced key)
CR2025
Owner's manual: manualowl.com (checked Nov 1, 2026)
Manual text: “Replace only with the same type battery (CR2025 or equivalent).”
Find CR2025 on Amazon - 2011Unknown
Not confirmed yet
Changing the battery
Separate remote fob
- The remote is a small standalone unit. You will not need to touch the ignition key at all.
- Find the slot along the edge and turn a coin in it. Go slowly so the clips do not snap.
- Replace the cell, keeping the + side where it was, and check the small metal tab still touches it.
- Snap the case shut and watch for the lights to flash when you press lock at the car.
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.
Smart key (push-button start)
- Find the small release on the edge or back of the fob and hold it while you pull out the metal emergency key.
- The gap left by the metal key usually has a pry point. A slow twist with a thin flat tool (tape on the tip saves the plastic) opens the two halves.
- Pop the old battery out with a toothpick or plastic pick, not a metal blade, and seat the new one with the + side matching the old one.
- Close the case until it clicks all the way round, put the metal key back, then try the buttons and a push-button start.
Mazda advanced keys usually have a knob or button that frees the auxiliary key; the cover lifts once the key is out.
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.
Coin cells are a choking and burn hazard for children. Store the spares in their original pack, out of reach.