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2-2 Electrical
Section 2: Electrical
Electrical Systems Management
Care must be given in deciding what equipment should be installed into a police vehicle given the
power demands of the equipment and the power available from the vehicle. A power load strategy
should be developed to minimize the risk of running out of power. Examine the proposed
equipment for vehicle installation. Add up the current requirements. If the current requirements
exceed what the vehicle can reasonably be expected to be able to provide, the battery will begin
discharging to provide the power to the equipment that the generator is unable to provide. After
some period of time, the vehicle will shut off as the battery voltage decreases to a level that
cannot sustain vehicle operation.
There are alternatives that can be considered to minimize system electrical overload. Consider
the current requirements of equipment before it is purchased and installed. Modern light bars and
radios use a fraction of the current than units made as recently as 1996. As the light bar is the
most power intensive unit installed on most police vehicles, considerable attention should be given
to its current requirements. Changes in officer habits while in the field can make a difference as
well. When a vehicle is sitting at an accident scene and no one is in the car, the A/C can be
turned off until the officer is ready to get back into the vehicle. The A/C is among the largest
current users of non-police equipment. As such, it can impact available power for other uses as
well.
Generator Output
On the Expedition Special Service Vehicle (SSV), the generator is controlled by the PCM.
The Expedition SSV has a 150-amp generator.
• Generator amp output.
— Maximum output for the Expedition SSV is 150 amps
• Generator drive ratio, determined by generator pulley size.
— 2.96:1
Charging Margins
Generator output varies with engine speed and ambient temperature. The worst case for police
vehicles is when the vehicle is idling for long periods of time on a very hot day. Lower engine
speeds while idling, coupled with high underhood temperatures that may approach 93°C (200°F),
combine to minimize power output from the generator. At the same time, electrical demand on the
vehicle is often at its highest because the A/C loads are added to the usual electrical loads
experienced in emergency situations.
Vehicle Component Electrical Loads
Vehicle component electrical loads are shown in the table below. Not all features are powered all
the time, so actual vehicle loads on the power supply system will vary.
2010 Expedition SSV Modifiers Guide, 07/2009