(a) Sketch and describe an arrangement for automatic connection of emergency batteries upon loss of main power. Include in your answer:

(i) Means of obtaining d.c charging supply from a.c mains (3)

(ii) A method of maintaining charge on lead acid batteries (3)

(iii) The arrangement to check the batteries operate at a loss of main power. (2)

(iv) The length of time for which emergency battery of passenger and cargo ship must provide power (2)

(b) write short notes on primary and secondary cells. (6)