Battery - CR2032 (Varta)

The CR2032 battery is the coin cell that runs half the house. Three volts, lithium, 20 mm across and 3.2 mm thick. It is in remotes, car keys, wall clocks, kitchen scales, calculators and a long list of smart home buttons and sensors.

• What a CR2032 battery runs in this house
• Lithium fails cleanly, which is a feature
• Buy more than one
• Sizes that look similar
• Other names

What a CR2032 battery runs in this house

The Logitech Harmony Companion remote, the Philips Hue Smart Button and the NodOn Z-Wave switch all take one. Outside the smart home it is in car keys, wall clocks, kitchen scales, bathroom scales, calculators and the little remote for something you have forgotten you own. It is the most common lithium coin cell there is.

Lithium fails cleanly, which is a feature

The voltage holds steady almost to the end and then drops, rather than sagging gradually over weeks. So a device on one of these works normally and then stops, instead of behaving strangely, dropping signals and making you doubt the device itself for a fortnight first. When something misbehaves oddly, the coin cell is rarely the answer; when it stops dead, it usually is.

Buy more than one

Shelf life is up to ten years. Given how many things in a house take this exact cell, a strip of them in a drawer is one of the few purchases that is genuinely never wasted. It is the battery most likely to be needed at an inconvenient hour.

Sizes that look similar

It is 20 mm across and 3.2 mm thick. The CR2450 looks like the same thing at a glance and is 24 mm across and 5 mm thick, so it will not fit a 2032 holder and a 2032 will rattle in a 2450 one. Check the number printed on the old cell rather than its appearance.

Other names

Also sold as DL2032 and KCR2032. Brand varies between deliveries; the specification does not.

A note on handling. Keep coin cells away from small children and pets, and dispose of used ones properly rather than in a kitchen bin. They are small, shiny and exactly the size a toddler will put in their mouth, and a swallowed lithium cell is a medical emergency rather than an inconvenience. Blister packs exist for a reason; keep spares in theirs until they are needed.

For the larger coin cell used by dimmer switches and keyfobs, see the CR2450. Wikipedia has a full reference on button cells and how the numbering works.