As you probably know, batteries are something you should always have on hand. You may need a battery to power an electronic device during a power outage. Or you might discover that your new toy or gadget needs a battery. It would be a real bummer if you didn't have the necessary batteries on deck to get your electronic devices powered on. Then you would have to get in your car and drive to the store and back. That's inconvenient. Don't let this happen to you. Keep batteries in your house so that you are ready for these sudden events.
When it comes to the thrilling world of batteries, the 9-volt variety is often overlooked. These batteries don't have a special code name like AAA batteries or CR123A batteries. They are just 9-volt. Their power supply is right in the name. Their boxy, rectangular design might also lead you to believe that these batteries are boring and dull. Nobody wants to be called a square. But don't let this fool you. The 9-volt batteries are actually some of the most exciting batteries that you will come across in everyday life.
For one, 9-volt batteries have the terminal leads right on the outside. Just like a car battery or a larger "black box" battery for a security system, the terminal inputs on a 9-volt battery are accessible. You can connect wires to them and use them to power small electronic devices you created yourself. They are also great for science projects that use small electronic devices. And many devices use 9-volt batteries for powers. The classic examples are handheld testing equipment, small toys, smoke detectors and more.
Unfortunately, battery companies decided that 9-volt batteries were less preferable to their cylindrical brethren. These include the AA battery and the AAA battery. As a result 9-volt batteries are not as commonly used today. Maybe the battery companies believed that being able to run wires to the battery was too dangerous for the average end user. Maybe they just wanted to go in a more cylindrical direction. We don't know for sure. But what we can say is that the 9-volt battery is sadly overlooked today.
But some electronic manufacturers know better, and they continue to put the classic 9-volt battery to good use. The battery is still commonly used in life-safety sensors like smoke detectors and carbon monoxide sensors. It is also often used in handheld electronic testing equipment, like voltmeters and other similar devices. You never know when you might need one of these handy rectangular batteries might be needed!