4 •
FUNCTIONS
• General
D250T is a 24V DC-DC battery charger for a dual battery system with a starter battery and
a service battery. D250T is designed to be used as an onboard charger, for charging and
maintaining a 24-volt service battery from the vehicle alternator when motor is running.
• Charging
D250T uses a 4-step automatic charging algorithm to charge the service battery with up to 10A
when a conventional alternator (constant voltage) is running.
• Starter battery under voltage protection
The charging process is automatically switched off when the engine is not running to prevent
discharge of the starter battery.
• Temperature compensation
The external temperature sensor will adjust the charge voltage according to actual temperature
of the service battery. The charge voltage is reduced at higher temperatures and is increased at
lower temperatures. The temperature sensor should if possible be attached to the Service Battery,
or as close to it as possible. (see figure 4)
• Battery separation
D250T separates the starter battery from the service battery when the engine is not running. The
battery separation protects the starter battery from being discharged, this eliminates the needs for
diodes and VSR relays.
• Service battery temperature protection
The external temperature sensor attached to the service battery is protecting the service battery
from high temperatures by switching off the charging process if the measured temperature rises
too high. The charger will automatically restart when the service battery temperature reduces to a
level level within the specified operating temperature.
• Equalizing the starter battery
In a 24V system, where we have two 12V batteries in series, the voltage in the two batteries can
be unbalanced, especially if there are 12V consumers connected to one of the batteries. When
the service battery is fully charged, the D250T will measure the voltage levels in both 12V starter
batteries. If there is a difference between the voltage in these two batteries, the D250T is will
equalize the voltage levels to increase battery performance and lifetime.
• Protects service battery from overcharging
D250T will not overcharge the service battery. When the service battery is fully charged D250T
will go into pulse charging mode to monitor and maintain the charge status battery. If battery
voltage drops too low the charging process will restart.
• SMARTPASS 120T
Fully compatible with SMARTPASS 120T to provide the ultimate power management solution for
dual battery systems.
• Remote status indicator lamp
There are no LED indicator lamps on the units themselves but there is a status signal lead attached
to the charger. This can be connected to a 24V lamp (Max. 2W) for remote indication of charger
status, in the driver’s cab or other places where indication is needed.
D250T
D250T
