If your digital watch stops functioning, don’t throw it out. Just throw out the battery. A new battery may be all you need. You should expect a watch to need a battery replacement every few years. Change the battery when the watch becomes slow, the backlight weakens or the readout fades.

Determine the type of battery required by reading the back of the watch. The battery identification number has 3 or 4 digits, and specifies which type of battery you will need for the replacement. If the battery size is not stamped on the back, then your owner’s manual will provide this information. Otherwise, you can look up the manual online by entering the brand name and model number in a web search. If necessary, you can remove the back from the watch to see the size printed on the battery itself.

Buy a new battery. Like watches, hearing aids also use button batteries. Therefore, drug stores usually have them for sale, if a nearby watch dealer isn’t available.

Pry off the back plate of the watch with a knife. A screwdriver will almost never be narrow enough to fit into the gap. A fingernail will almost never be strong enough to dislodge it. Look for an indent under the watch back where you can insert the knife edge. Work the knife all the way around to lift off the watch back.

Replace the battery quickly. You may be able to preserve the watch’s memory if you make the switch quickly enough. If not, then you will have to reset the date and time. The switch should easily take less than 30 seconds. The watch back may need to be put back on quickly as well, if that is necessary for the battery’s circuit to be closed.