Garmin, Wahoo and CatEye put a CR2032 coin cell in the speed and cadence sensors listed here, while the Garmin and Wahoo head units charge a built-in battery.
Who made it?
Which one?
The battery it takes
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Sensors, head units and lights
Bike computer, sensor and light batteries by maker
Device
Kind
Battery
Garmin Speed Sensor 2, Cadence Sensor 2
Sensor
CR2032
Wahoo RPM Speed, RPM Cadence, TRACKR Speed
Sensor
CR2032
CatEye ISC-12
Sensor
CR2032
CatEye Padrone Smart, Strada Smart
Computer
CR2032
SIGMA BC 10.0 WL
Computer
CR2032
SIGMA BC 14.0 WL
Computer
CR2450
Garmin Edge 540, Wahoo BOLT, ROAM
Computer
Built-in rechargeable
Garmin Varia RTL515, Knog Plus
Light
Built-in rechargeable
Knog Blinder 900
Light
Built-in 21700, USB-C
From each maker’s manuals and product pages. Other models may take a different battery.
Coin cells with a bitter coating
Some coin cells are coated with a bitter taste to put children off swallowing them. Wahoo doesn’t recommend them in its sensors, naming Duracell’s as an example, because the coating can lower battery performance and briefly weaken the sensor. It suggests Panasonic or another name brand instead.
Opening a Wahoo RPM sensor
Twist a coin in the notch on the sensor’s side to pry off the face plate. Wahoo suggests a US dollar coin or a nickel rather than a quarter.
Swap the old cell for a new CR2032.
Check that the rubber O-ring sits properly before closing it.
O-ringaround the CR2032Face platepried off
Inside the sensor: the CR2032, with the rubber O-ring round it that the face plate closes on.
CR2032 against CR2450
The two aren’t interchangeable. The makers’ datasheets put a CR2032 at 20 x 3.2 mm and a CR2450 at 24.5 x 5 mm, diameter by thickness, both 3 V lithium.
Coin cells and children
The National Capital Poison Center says that if anyone swallows a battery, immediately call the 24-hour National Battery Ingestion Hotline at 1-800-498-8666 or your poison center at 1-800-222-1222. Don’t delay. Immediate treatment decreases severity.
Common questions
Can I get a new battery for an original Wahoo ELEMNT?
No. Wahoo built the first ELEMNT with a replaceable battery, but says replacement batteries for it are no longer available.
Which way up does a CatEye battery go?
In the Padrone Smart and Strada Smart, CatEye says the (+) side faces up. In the ISC-12 sensor, the (+) side should be visible before the cover closes.
From Garmin, Wahoo, CatEye, SIGMA SPORT and Knog manuals, support articles and product pages, with coin cell sizes from the makers’ datasheets, read on October 25, 2026. Checked against published data from Garmin, Energizer, Wahoo Fitness, National Capital Poison Center and CatEye (plus 2 more).
See all 11 sources
Energizer, CR2032 product datasheet (PDF)
Energizer, CR2450 product datasheet (PDF)
National Capital Poison Center, Button battery ingestion (poison.org/battery)
Garmin, Varia Rearview Radar RTL515/RTL516: Specifications
Wahoo support: ELEMNT, BOLT, and ROAM FAQ; ELEMNT BOLT 3 (2025) Product Information
Wahoo support: replacing the RPM Speed or Cadence battery and the TRACKR Speed battery
CatEye, Padrone Smart and Strada Smart manual: Battery replacement
SIGMA SPORT product pages: BC 10.0 WL and BC 14.0 WL
Knog product pages: Plus Rear Bike Light and Blinder 900 Front Bike Light
Battery sizes come from battery makers' datasheets and device makers' own manuals and help pages. Check your device's manual or the old battery before you buy. If anyone may have swallowed a battery, call the National Battery Ingestion Hotline at 1-800-498-8666 or your poison center at 1-800-222-1222 straight away.
