A Dash Cam Power Supply That Won't Kill Your Car Battery

Dash cameras are extremely popular, especially outside the United States (though they're picking up steam here, too). They're a fantastic resource for drivers concerned about liability, as they can help prove who was at fault in an accident, see who broke into the car, and possibly even prevent such break-ins altogether. But dash cams pull power from the car's electrical system, which means they drain the battery when the car's engine is not running. To prevent flat batteries, Kuzysk designed this dedicated power supply for dash cams.

Cars with internal combustion engines contain alternators, which are small dynamos (like in generators) turned by a belt that produce electricity. When the car's engine is running, the alternator provides power to the various accessories (headlights, stereo, gauge cluster, etc.) and charges the battery. When the car isn't running, the accessories must pull their power directly from the battery. Modern cars have many components that always require a small amount of power and drain the battery. If the car sits for too long without running, those will eventually kill the battery and make it impossible to start the car without a jump. A dash cam adds to the drain and can dramatically reduce the time it takes for a car battery to go flat.

This device sits between the dash cam and its connection to the car's power. When the car is running or when the battery voltage is at a healthy level, it allows power to pass through to the dash cam so it can operate as it should. But if the power supply voltage is below a set threshold, such as when the battery is starting to die, the device cuts off power to prevent the dash cam from continuing to drain the battery.

There are commercial products for this same purpose, but Kuzysk says that this works better. They claim that this draws "50 to 100 times" less power in the off state.

This device requires a custom PCB with several SMD (surface-mount device) components, so it isn't a project for people inexperienced with soldering. That PCB contains an ATmega328 microcontroller, which is the same found in the Arduino Uno and many other development boards. It monitors the voltage from the car through an LM2596M-5.0V buck converter. A set of DIP switches let the user select a power mode.

The code is quite simple and includes a couple of different modes. One will only allow power to reach the dash cam when the car's engine is on or the key is turned to ACC (accessory power on). Another timer mode will let power reach the dash cam for set amount of time after the car's engine turns off. The last mode will let power reach the dash cam indefinitely, until the battery voltage drops below the set level.

If you use a dash cam and have problems with it draining your car's battery, then this is exactly what you need to solve that issue.