The most popular 9V battery by far is the 9 volt block battery. 9V batteries have a voltage that is six times higher than that of an AA or AAA Battery. They often house literally six AAA batteries. They are often used in smoke detectors but also in effect pedals for electric guitar, for instance. You can charge the rechargeable batteries by means of a Battery Charger. You might also want to check out the rest of our wide range of Batteries & Chargers.