24 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 25
SECTION 7 |
Preparing the Charger for Operation
7.6 REDUCTION OF MAXIMUM CHARGING CAPACITY TO HALF FOR
SAFE CHARGING OF LOWER CAPACITY BATTERIES - HALF POWER
MODE
Batteries should not be charged at very high currents to ensure long life. Unless ap-
proved by the manufacturer, the maximum charging current should be limited to
approximately C/10 (w
here C is the Ah capacity of the battery at 20 Hour Rate
). Thus, at
the rated Bulk Stage Current capacities (
50A for SEC- 1250UL and 25A for SEC-2425UL
),
the Ah capacity of the battery that should be charged with the charger will be:
• 50A x 10 = 500 Ah for SEC-1250UL
• 25A x 10 = 250 Ah for SEC-2425UL
If battery with lower Ah capacity is charged at the full charging rate, the battery life is
likely to be reduced.
A provision has been made to reduce the maximum charging current to approximately
half: 25A +/- 1A for SEC-1250UL & 12.5A +/- 1A for SEC-2425UL. This mode is termed as
“Half Power Mode”. This mode can be selected by pressing push switch marked “Half
Power Mode” (
8 in Fig 3
). When selected, a Green LED marked “Half On” (
5 in Fig 3
)
will be lighted. When “Half Power Mode” is selected, batteries with the following lower
capacities can be safely charged at C/10 charging rate:
• SEC-1250UL - 250 Ah
• SEC-2425UL - 125 Ah
7.7 BATTERY TEMPERATURE COMPENSATION
The cell voltages of a battery depend upon the temperature of the cells inside the bat-
tery. The cells have a Negative Temperature Coefficient - their voltage levels increase
at lower temperature and decrease at higher temperature. The Negative Temperature
Coefficient is - 28 mV / ºC for SEC-1250UL & - 56 mV / ºC for SEC-2425UL.
The battery and battery charger voltages are normally specified at a temperature of
77ºF / 25ºC. Thus, if the battery temperature is considerably lower than or higher than
77ºF / 25ºC, it will be under-charged or over-charged unless the battery charger has
temperature compensation.
7.8 BATTERY TEMPERATURE SENSOR MODEL TF-500
Battery Temperature Sensor Model TF-500 (
14, Fig 3
) has been provided with the unit. It
comes with 5M long cable. It has an adhesive backed Temperature Sensing Element (
14A,
Fig 3.1
) on one end and 3.5 mm diameter Plug (
14B, Fig 3
) on the other end.