AirTag battery is running out too quickly

I set up an airtag, and installed a new battery, since it said the battery was low. 2 days later, I got a notification that that battery was low again. I keep changing the battery and it only lasts about a day or two each time. The new batteries I install read 3.25 V and after they are declared “low”, the voltage is down to about 3.05. They are nominally 3 V batteries. Is this likely a problem with the batteries or with the AirTags?