Battery Discharge Prevention

If you purchased a dash cam that has a parking mode / parking surveillance option which requires you to hardwire the camera into your vehicle, you may want to consider a battery discharge prevention device.  This device goes by many names:

  • Battery discharge prevention device
  • Uninterrupted power cable
  • Low battery cutoff
  • Battery protector
  • Electric power controller
  • Power magic

What is it?

Regardless of the name, this device is connected to your dash cam’s power supply and hardwired into your vehicle.  The device can prevent the discharge of the vehicle battery by blocking power to the dash cam if the voltage drops below a configured value or if the configured time has elapsed.

Is it necessary?

Many people would argue that a battery discharge prevention device is necessary however this depends on 2 factors.  The first factor is how often you drive your vehicle.  If you drive it daily, a typical dash cam will not drain enough power from an average car battery for a problem to occur.  In fact, many people have left their vehicles for 2 or more days in parking mode without any problems with battery discharge.  If you will not be driving your vehicle for a few days, you could unplug your dash cam to prevent battery discharge.

The second factor is your car battery’s condition.  If it is a newer battery in good condition, the dash cam will unlikely drain the battery for numerous days.  If your battery is not in good condition, you will likely need to replace it anyways and a battery discharge prevention device will just delay the inevitable replacement for a few weeks.

However, given the relatively low cost of these devices, many people would rather not face this battery discharge risk.  Overall, they are a reasonable device to consider but not 100% necessary depending on your driving behavior and  battery condition.

What is the ideal voltage cut-off?

Unfortunately this is not a clear cut question.  Lead Acid start batteries typically found it vehicles should not be routinely deep cycled or that will reduce the life of the battery.  Hence, if you never want to deep cycle your battery the cutoff needs to be 80% or 90%. This equates to a voltage cut-off of around 12.4V.  Very few battery protection devices have this setting.  If your battery protection device cut-off is 12V or 12.2V, the battery will deep cycle if it hits this number reducing the life expectancy of the battery.

The following table estimates the voltage associated with a typical 12V lead acid battery’s percentage charge for a variety of temperatures.  Note that these voltages are approximate estimates based on an unloaded battery (not when charging).

Temperature (F)Temperature (C)100% Charge75% Charge50% Charge25% Charge0% Charge

The above table is important when choosing a device since you want to make sure the voltage cut-off is adequate.  For example, a voltage cut-off of 11.6 is equal to a completely dead battery when it is warmer than 57 degrees F or 14 degrees C.  Really not a good cut-off in most conditions but some devices have this setting or lower.