Principles Of Operation; Temperature Compensation - KUSSMAUL AUTO CHARGE 091-127 Series Instruction Manual

PRINCIPLES OF OPERATION

A three-step lead acid battery charger operates in the three stages described below:
1) A discharged battery is recharged at a constant current (bulk charge) until its voltage
reaches an overcharge level of 2.48 volts per cell. At this time the charger will switch
to Finish Charge. The battery accepts 75-85% of its capacity during bulk charge.
2) This overcharge voltage is now maintained constant at 2.48 volts per cell (absorption
or finish charge) until the charge current tapers down to {battery capacity/35}
amperes. For the 12 volt, 80 ampere charger this current is 11.9 amperes. The battery
accepts 15-25% of it capacity during absorption charge.
3) Once the charge current reaches the tapered down value (see above), the voltage is
set to a float voltage of 2.24 volts per cell, and maintained at float charge. The battery
is maintained at full charge during float charge, and the green indicator labeled "Battery
Charged" is illuminated.
Figure 1 depicts the above described operation. Note that the term "absorption charge" is
used interchangeably with "finish charge". Upon application of AC power, the charger is
placed into bulk charge. When the charger switches to finish charge, a timer starts. In the
event that the charge current did not taper down to approximately C/35 amperes after 2 ½
hours, the charger will automatically go to float charge, and a time-out will be indicated. This
time-out indicator can indicate an old or leaky battery, or it can indicate that the charger is
undersized for the battery being charged.
A battery fault indicator is provided to indicate the absence of a battery, a battery connected
with reverse polarity, or a battery with an open circuit terminal voltage of less than 1.35 volts
per cell.

TEMPERATURE COMPENSATION

Temperature compensation is provided as an optional feature. A temperature probe is
provided which can be placed in the air surrounding the battery or bonded to the battery
case.
SELECTABLE OUTPUT CURRENT
Selectable output current level is provided as an optional feature. It is normally supplied as
a current output level "HIGH" and "LOW" front panel switch selectable setting. Unless
otherwise specified the "HIGH" current setting refers to unit maximum output currrent as
specified in Specifications section of this manual. The "LOW" current setting is 40% +/- 5%
of the maximum current ouput. Consult factory for additional information on this option.