Alpha Technologies AlphaCell SMU-HR - Manual (Page 11)

11 745-680-B2-002, Rev. B
NOTE:
Refer to your particular charger’s manual for specific instructions regarding charger setup and operation.
2.0 Charging Procedures
During operation, verify batteries are:
Float-charged in order to maintain a fully charged condition during the standby period. •
Completely recharged after a discharge. Recharge as soon as possible to ensure maximum •
protection against subsequent power outages. Early recharge also ensures maximum battery
life.
While recharging procedures vary depending on the recharge time and battery life, generally charging
is performed as follows:
At a voltage equal to the float voltage and a low current (long recharge time); •
At a voltage not higher than 2.4Vpc and a high current (faster recharge). •
The IU recharge method, also known as modified constant potential, has been used for many years
and in a variety of applications. It satisfies the need to have the battery quickly recharged while
ensuring maximum battery life.
Recharge at a constant current rate until the voltage reaches a pre-set value. 1.
Maintain the pre-set voltage and decrease the current until a minimum defined value is 2.
reached.
Complete the recharge at a final constant voltage value equal to or less than that defined for
3.
float charge and decrease the current to the value used in float.
Temperature °F (°C) Recommended Float (Vpc)
-4 (-20) 2.37
32 (0) 2.32
68 (20) 2.27
77 (25) 2.26
140 (60) 2.17
2.1 Float Charge
2.27V at 68°F (20°C) is the recommended voltage for float charge. This voltage ensures the
maximum life of SMU-HR batteries. These batteries can operate over a temperature range of -4°F
(-20°C) to +140°F (+60°C). Performance and life are greatly reduced outside of this temperature
range.
The equation to determine float voltage at a given temperature is:
V = 2.32 - 0.0025 * T (where V= Float Voltage and T = Temperature)
or
-2.5 mV per 1.8F (1C) temperature fluctuation outside of 68F (20C)
The minimum and maximum recommended voltages are 0.010V on either side of the determined
voltage at a given temperature. Batteries floated at voltages above the range will have an increased
risk of dry out, grid corrosion and thermal runaway. Batteries floated below the range will not receive
enough charge, and will be subject to sulfation.
Table 2-1, Float Voltage at different Temperatures