Battery - CR2450

The CR2450 battery is the larger coin cell, for dimmer switches and keyfobs. Lithium, 3 volts, 24 mm across and 5.0 mm thick. It looks like a CR2032 but it is wider and thicker, and holds a good deal more.

• A CR2450 battery is not a large CR2032
• 550 mAh is a lot for a coin cell
• What takes one here
• It is built not to leak
• Equivalents

A CR2450 battery is not a large CR2032

They look like the same thing on a shelf and they are not interchangeable. This one is 24 mm across and 5.0 mm thick against 20 mm and 3.2 mm, so it will not go into a 2032 holder and a 2032 will sit loose in this one and lose contact. Read the number stamped on the old cell before ordering rather than judging by eye, because this is the commonest wrong battery bought in a smart home.

550 mAh is a lot for a coin cell

That capacity is why this size ends up in the devices people actually press many times a day: a wall dimmer, a keyfob, a remote. A 2032 in the same job would need changing several times as often, which is exactly the annoyance that makes people stop using a device. Manufacturers choose this cell when they expect the thing to be used, not admired.

What takes one here

The Philips Hue Dimmer Switch, the Fibaro KeyFob and the Wyze Motion Sensor. Outside the smart home it suits watches, thermometers, calculators and electronic notebooks.

It is built not to leak

Stainless steel construction with good sealing, and mercury free. Leakage into a holder is what ruins the device rather than just the battery, and it is worth caring about in a wall dimmer you would rather not replace.

Equivalents

DL2450, ECR2450, GPCR2450 and CR 2450 are all the same cell. Brand varies between deliveries; the specification does not.

Keep spare coin cells in their packaging and out of reach of small children and pets. A swallowed lithium cell is a medical emergency, not a wait and see. Dispose of used ones at a proper collection point rather than in a kitchen bin, since a partially discharged cell can still short against metal.

If the device actually takes the smaller coin cell, that is the CR2032. Wikipedia sets out how button cell numbering encodes the diameter and thickness, which is how you read the number on the old one.