Samlex America SCC-30AB - Manuel (Page 20)

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GENERAL INFORMATION: BATTERIEs
application. As per Table 3.2 on page 13, the usable capacity at this higher discharge
rate will be reduced to 60%. The actual capacity of the battery will have to be
increased by 1.66 times.
f) Further, for longer battery life, the battery should not be discharged deeply (Please refer to
heading “Depth of Discharge and Battery Life” on page 14). Normally, depth of discharge
should be limited to 80%. Hence, the actual battery capacity will have to be increased to 1.25
times the backup energy consumption to compensate for this limitation.
g) The actual battery capacity will, therefore, be equal to 1.66 x 1.25 = 2.07 times or say 2 times.
h) For example, if the total battery energy consumption as per the above calculation at (d) is say
200 Ah, the capacity of the battery bank will be 2 x 200Ah = 400Ah..
Battery Charging Stages and Charging Currents
It is recommended that the batteries may be charged at 10% to 13 % of the Ampere
Hour capacity of the battery (20 Hour Discharge Rate). Also, for complete charging
(return of 100 % capacity), it is recommended that a 4 stage charger may be used:
• Constant Current Bulk Charging, followed by;
• Constant Voltage Boost / Absorption Charging, followed by;
• Constant Voltage Float Charging, followed by;
• Constant Voltage Equalization. Equalization is carried out only when some cells do not
charge fully and the individual cell Voltages differ by more than 0.2V cell. Also, equalization
is carried out only for non-sealed / vented / flooded / wet cell batteries.
Requirements of Battery Charging in Solar Systems
Batteries in Solar Systems are commonly subject to abusive conditions that are
generally due to:
• Under charging due to low sun peak hours
• Excessive charging in high sun peak hours
• Inappropriate or ineffective charge control for the battery technology
The individual or combined effects of sun peak hour changes, poor charge control and
the daily load changes can be potentially damaging to the battery. Cheaper charge
control strategies such as simple ON/OFF PV array shedding (Non PWM control) will
generally provide the battery with sufficient charging current to complete the Bulk
Charge Phase which will return the battery to 80% State of Charge. After the Bulk
Charge Phase, the Taper or Absorption Charge Phase is very important in preventing
stratification, hard sulfation and pre-mature capacity loss.