1) DC power supplies and backup batteries provide a reliable power source for telecom equipment and ensure continued operation even when main power fails. 2) DC power is needed because telecom equipment uses DC and batteries can only be charged with DC power, which is produced from AC mains by a rectifier system. 3) When the mains power fails, the batteries supply power to the telecom equipment until mains power is restored, at which point the rectifier system recharges the batteries.

1. Why do we need ELTEK Power Supply? - And why do we need Batteries? ? Why Power & Batteries

6. Overview/Components in a Power System NONE PRIORITY LOAD LOAD (pc’s or different voltage) UPS AC/DC - DC/AC ALARM MODULE Rectifier #1 Rectifier #2 Rectifier #n G OVP MAINS FUSES LVBD BATTERY DISTRIBUTION BATTERY BANK DC-DC or DC/AC REDUNDANT RECTIFIER SYSTEM AC/DC DIESEL GENERATOR Rectifier #n LVLD Battery & Load Distribution PRIORITY LOAD BATTERY BANK

10. Voltage Sequence in a DC Power System Float charge Battery discharge Battery recharge Mains failure t U 53.5 43.2 -w/current limitation Disconnect Voltage (43,2 / 24=1,8v) Mains resume Charge Current Limitation Normal charge current

13. Open Circuit Voltage in relation to state of charge of the cell. State of charge (%) V DC 1.90 Open Circuit Voltage (per cell)l 1.95 2.00 2.05 2.10 2.15 25 50 75 100 0 Charge Voltage Open Circuit Voltage

14. Float Voltage versus temperature (Example from Exide) END OF SESSION....