How to Change the Battery For Your Omron HJ-303 Pedometer
You see that blinking battery with the cross on it on your pedometer? That means it's time to change your battery! You can take your time with the battery change—it's not doing to die on you overnight. My pedometer started blinking the day I started the Crater Lake hike so I didn't have a chance to replace it for nearly a week, but the old battery kept on ticking.
These pedometers use a CR2032 button battery which you can often find at even small convenience stores. It will certainly be available at your local CVS or Walgreens.
You'll also need a very small screwdriver to change the battery. My pedometer included a small, flat-head screwdriver, which sounded great until I tried to use it and discovered it was still too large to actually work on the pedometer it was sold with! I had a small Phillips screwdriver at home that worked well enough. (The screw can take either type—as long as the screwdriver is small enough.) If you don't have the right-sized screwdriver, though, don't go out and buy one. The folks manning those counters for electronic devices near the batteries will likely have one behind the counter that you can use, so ask the workers there if they can help you out.
When to Change Your Battery
Besides the obvious—when your pedometer tells you it needs a battery change—the best time to change the battery is shortly after the top of the hour. This pedometer counts steps for each hour, storing the counts in memory that will be lost as soon as the battery is removed. It's a temporary memory and any step counts you have for that hour will be lost. At the top of the hour, the pedometer will transfer the counts to a permanent memory that will not be lost when the old battery is removed. Consequently, to not lose step counts—or at least to minimize them—change the battery shortly after the top of the hour.
Not like I did. When I tried to change my battery at 12:51 PM. (Don't believe the time on my pedometer. I never changed the time since the end of Daylight Savings.) After having walked about 5,000 steps since 12:00 PM. Which will all be lost, but could have been saved had I waited nine more minutes before changing the battery.
Change the Battery... NOW!
Unscrew the small cover on the back of the pedometer. Be careful not to lose the screw! It's a tiny little thing!
Pop out the old battery. See that small notch near the top of the battery in this photo? You'll have to get something thin in that such as a fingernail. Push downward (towards the writing) and the battery will just pop right out once it clears the tabs on both sides of the notch.
Pop in the new battery. Insert the battery at the end with the "Walking style" first. Make sure the 'flat' side with the writing is facing you! Push the top of the battery down a bit—down towards the "Walking style" text, and once the top of the battery clears the tabs near the top, it'll pop right in.
Once the battery has been replaced, the time will be blinking. (You can't see the blinking in this photo, obviously, but it will be blinking.)
Go ahead and reset the time just like you did when you configured your pedometer. You can skip the first step since you'll already be in setup mode, but otherwise, all the other steps are exactly the same. It will take you through the entire sequence of updates—time, weight, height and stride—but the other settings will have been stored in permanent memory and won't need fixing.
Battery Change is Done!
One thing you'll notice between this last photo and the first one... my step count for the day fell from 5,208 to 221 steps. My step count was 221 at 12:00PM—the last time the pedometer stored my step count in permanent memory.
The 4,987 steps I took between 12:00PM and 1:00PM stored in temporary memory were lost, but like I said before, you can avoid this fate by waiting until after the top of the hour to change your battery rather than just before the top of the hour.