1. The battery may not be the problem
Check the device first. An old stock battery has less capacity than a fresh one of the same code, so a tired battery makes the device look like it’s draining fast.
2. Signal strength eats power
A tracker or key fob that’s far from its phone, or shut inside a metal box, uses much more power looking for a signal. The battery goes faster because the radio is working harder.
3. Cold makes batteries weaker
In a car in winter, or outdoors, a lithium coin battery gives less power and looks flat sooner. Warm it in your hand before you decide it’s dead.
4. The device itself got busier
Newer firmware, more syncing, a screen that stays on, or an app running in the background all use more power. A restart and a software update can fix a lot.
5. Leaking or corroded contacts
White crust around the battery means the old cell leaked. The new battery may be perfectly good, but corroded contacts make it drain quickly. Clean them or replace the holder.
6. Some things are just built that way
A fitness band with a screen, a GPS watch and a camera with a flash all draw far more than a key fob. Compare against another device of the same kind before you blame the battery.