A dash cam battery is a stand alone battery pack that powers your dash camera when your vehicle is off. They are used to provide safe, reliable power to the dash camera for parking mode use (powering the dash cam when the vehicle is off).
Using a dash cam battery assures your vehicle battery (the one used to start the vehicle) will remain fully charged and ready to start your car. This is because power required by the dash camera is drawn from the dash cam battery, and not the main starting battery of the vehicle.
The vehicle only recharges the dash cam battery while the engine is running, when the engine is off, the vehicle does not send power (or consume power) from the dash cam battery at all. This is because the positive input of the dash cam battery is connected to an ignition or accessory power source, which only comes on when the vehicle is running.
Many newer BMW vehicles use a complex battery management/monitoring system that monitors the charge state of the vehicle starting battery, as well as the over-all current draw of the vehicle systems when the vehicle is off. When you add a dash camera, and have it running when the vehicle is off (parking mode), the battery monitoring system will detect this additional power (current) draw, and trigger a warning message notifying you of excessive power consumption while the vehicle is off. As the vehicle battery gets drawn down lower, the battery monitoring system will start to turn off vehicle accessories such as proximity key-less entry, puddle lighting systems, and more. Here is what the error message can look like:
The solution to this issue on BMW vehicles is to have your camera turn on/off with the vehicle OR if you wish to use parking mode, add a dash cam battery.
Dash cam batteries are not water proof, so they MUST be installed inside (interior) the vehicle, away from moisture. If there is room under the vehicle dash board, we recommend they be installed there. Alternatively the trunk of the vehicle or the spare tire area of the vehicle is a good mounting location as well. In BMW, Audi, and Mercedes vehicles, we recommend installing the dash cam battery in the trunk, either next to the vehicle battery (which is generally in the trunk of these vehicles), or near the rear fuse block location in these vehicles.
Dash cam batteries can be re-charged at home or outside the vehicle (adaptor purchase may be required), if this is something you wish to do with your dash cam battery then mounting location should factor this in and the battery should be mounted in such a way as to be easily accessible and removable.
Take a look at the picture below showing the install of a Cellink B in a BMW 5 Series:
You can buy a dash cam battery at Lockdown Security, we carry a wide selection of dash cam batteries, which you can see in the link below: