According to Brita[
brita.com] the battery is supposed to last five years (mine didn't) and is not replaceable. It could and should be replaceable but it's just another example of planned obsolescence to make people spend more money.
When my battery died I decided to see if I could change the battery and keep using the electronic indicator without replacing the Brita. I searched online and didn't find any resources on replacing the battery so I went into MacGyver mode and figured it out myself.
To do this you'll need a flatheat screwdriver, pliers and a CR1616 button cell battery.
Click on the thumbnails to get larger pictures for more detail. I hope that you are able to follow along and replace your battery as I did.
1. The first step is popping the electronic indicator out of the pitcher lid. I used a flathead screwdriver and wedged it between the corner of the timer and the lid until I worked the timer module out. As you can see there is a little damage done to the corners of the lid and indicator module.
2. On the long side of the indicator housing's seal (on the bottom) is a plastic lip. Identify the lip, this is what it looks like. There are two lips, one on each side of the indicator housing.
3. Use your screwdriver to fold one of the plastic lips up.
4. The bottom of the indicator housing is a clear plastic seal. You need to remove the seal from the bottom of the indicator housing. Use pliers to pull this plastic seal off using the lip which you folded up. This is the hardest part because the seal is strongly glued to the housing. Keep working the seal until you've removed it. The seal will most likely be destroyed in the process. Here is what mine looked like when I started the process.
5. When you've got the plastic seal off you can remove the battery. There is a metal fastener that holds the battery in. Remove the fastener to get the old battery out.
6. Insert new battery and replace battery fastener.
7. When I put the new battery in the timer module didn't come right on. Not sure what to do at this point I touched the exposed copper contact with the screwdriver head and that seemed to complete some kind of circuit which caused the timer to come back on.
8. Reset the timer (if necessary) by holding down the start button in the normal fashion.
9. Re-seat the timer module into the Brita pitcher lid. I did not put the timer all the way back into the lid so that I could more easily remove it in the future. The timer module is no longer water proof since you removed the seal so if you ever want to wash the pitcher lid you'll have to remove the timer again. You also have to remove the timer module to replace the battery in the future.