• The DC charging supply is obtained from the main busbar. A transformer will step down the voltage to required charging voltage and a rectifier will provide DC voltage at required charging emf
• When charging from a discharged state, emf is supplied through a branch ‘A’ at full charging voltage
• A voltage monitor ‘V’ monitor the voltage of the cell and gets energised when cell its full charge emf of 2.2V/cell.
• ‘V’ closes contact V1 and energises contact ‘TC’, then TC 1 gets open and TC2 gets closed and current passes through a resistor for trickle charging.
• When main power failure occurs, the contactor KM gets de-energised, so contacts KM1 & KM2 get open and KM3 & KM4 are closed.
• Opening of KM1 & KM2 isolates the battery from charging circuit and KM3 and KM4 closes to allow the battery to supply to emergency services
• A test switch provides means for testing the battery.

Method of maintaining charge:

• Full charge/ Quick charge/ burst charge: when the battery is discharged on load or otherwise full charge switch is switched ON to charge the battery
• Trickle charge/ float charge: batteries get discharged when not in use due to local actions so it is kept on trickle charge where very small amounts of current is supplied just to make up for the loss of charge.

To check operation at loss of main power: test switch is pressed which simulates loss of main power and the charging contacts open and load contacts is made

Duration: for transitional power source 30 minutes for both passenger and cargo ship