Date: 7.5.2012
Version: 1.00
P7000-K Owner’s Manual
GENERAL INFORMATION
PROBLEM
On applications where liftgate batteries are mounted a long distance from the primary vehicle’s electrical system,
voltage drop will occur. The longer the distance and the smaller the cables that connect the two battery systems, the
greater the voltage drop. To charge these liftgate batteries, the correct voltage must be applied to these batteries.
Without the necessary voltage (electrical pressure) to push current through the liftgate batteries for recharging, no
recharging can occur. To charge a group 31 flooded cell battery at 0 degrees F, voltages of 15 volts are necessary. The
same battery pack at 80 degrees F might only require 14.0 volts. The heavy-duty commercial vehicle alternator is
normally set at 14.0 volts and flat compensated. The typical vehicle’s battery pack is maintained at approximately 13.5
volts. The difference occurs because of the voltage drop between the battery and the alternator. With this fact in
mind, the starting voltage for the liftgate batteries is 13.5 volts.
The circuit to charge the liftgate batteries includes the cables from the vehicle's battery box to the dual pole
receptacle at the back of the tractor, the dual pole cable from the tractor to the trailer, the receptacle at the front of
the trailer, and the cable that connects to the liftgate batteries. The total length of this can be well over 60 feet. All of
this length and connections (including fuses) create voltage drop in the system. While the total circuit resistance of
this circuit is constant, as the current load increases, the voltage drop also increases. It is impossible to have the
correct level of voltage at the liftgate batteries. This reduced voltage results in a battery pack that is not maintained at
a proper state of charge, which results in shortened battery life, less operating time and possible damage to the
liftgate motor.
SOLUTION
TRAIL CHARGER –Eliminates the above problem by amplifying (boosting) any input voltage (9 to 14) to the correct
voltage necessary to charge and maintain the liftgate batteries. This input voltage can be obtained through the 7-way
auxiliary pin, which now allows the liftgate batteries to be charged when connected to any tractor with no dual pole
connection necessary. This increased voltage will allow the batteries to be charged and maintained at a higher state of
charge so that they provide the energy necessary to do whatever job they are designed for, even in the toughest
environments. The Trail Charger also will not let the liftgate batteries back feed to the tractor’s battery pack.
The Trail Charger with Lockouts has a shutdown mode of operation:
Shutdown Mode: This mode is enabled when the lock out pin is active. In this mode the charger output is shutdown
and will not charge an external battery. This mode has the highest priority and overrides all other modes. This feature
is used when the Trail Charger is powered off of the aux circuit. A lead is connected to the stop light circuit to the six
pin connector of the Trail Charger with Lockouts. When the brakes are applied the Trail Charger with Lockouts turns
off so that the trailer’s ABS system gets full available power. When the brakes are released the Trail Charger turns back
on.
This system provides three ways to power the Trail Charger. Dual pole, single pole or from the aux circuit of the
seven way. Any tractor can provide power the Trail Charger with this system. It automatically selects the correct
source.
