Eli5: Why do domestic fire alarms take a rectangular battery instead of AA/AAA?
In: 12
Like any mass market consumer product, companies seek to reduce the costs of their products as much as possible. One way to do this is to reduce the number of components required and so smoke detector chips such as the NXP MC145017 were created that integrated many of the components of a smoke detector in a single device. These chips have a recommended input voltage of 9V so the easiest (and cheapest because a 6xAA batter holder costs more money) to get the recommended 9V is one 9V battery.
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