With the F80/F82 generation of M3 and M4, a new challenge arose with hardwiring dash cams. Due to the expensive lithium battery in these vehicles, the car's computer is quite sensitive to any external and unexpected drains to the battery. When we first started hardwiring dash cams to run parking mode off of the car's battery, we noticed that customers would talk about battery drain error messages on the dashboard and iDrive. Furthermore, they would also complain that the comfort access (proximity key entry) would disable itself and they'd be forced to use the unlock button on the key fob to unlock the door. This is because the car's computer, in an effort to reduce battery drains, disables the comfort access feature to preserve the charge of the battery.
Understandably, anyone with a high end sports sedan like the M3 would want to protect it in the event of a hit and run or vandalism. So what if you want parking mode recording but don't want to harm your vehicle's battery? The answer is the Blackvue B-124 battery pack which can be either hardwired or charged via the cigarette socket. This battery pack is charged up while driving but becomes the sole source of power for your parking mode dash cam when the engine is turned off. The Blackvue DR900S-2CH can run for just shy of 20 hours in parking mode so overnight recording is definitely possible.
For newer BMW's we prefer using the hardwire method over the cigarette/12V socket method for the battery pack for three reasons.
- Faster charging time; this applies to all cars but essentially in hardwire mode the battery pack can charge at 9 amps vs. only 5 amps through the cigarette plug. This is due to excessive heat that can damage the cigarette plug
- On these newer BMW's the 12V/cigarette sockets typically stay on for 10 minutes after the engine is shut off. During this time, the battery will keep on charging but will drain power from the car's battery. To fully eliminate the drain on the car's battery, we can hardwire to a fuse that shuts off right away when the car is turned off.
- Cleaner wiring! The male cigarette plug of the battery pack will protrude whether you use the one in the center console or the one in the trunk. Because it sticks out, it can also be prone to damage if moving larger objects in the trunk. When you can't see the wire, it makes the interior of this luxury sedan look that much better.
Another tip is to mount the rear camera off center of the third brake light if you want the cleanest look. The design of the third brake light on the 2, 3, and 4 series makes it so that there's no discreet way to run the wire over, around, or through the third brake light housing! For mounting the battery pack, there's a large compartment under the trunk floor that's perfect for putting the battery and even an expansion pack if necessary.
Due to warranty and servicing complications related to draining the factory battery, we strongly suggest getting a battery pack if you want parking mode on your late model BMW. The car's computer will log a record of low voltage warnings and the service department will know if you have that external drain. Replacing the lithium battery in these cars can cost upwards of a thousand dollars as well, so anything that can prevent stress on that component is well worth it.