The watt hour efficiency of a lead cell varies between and %.

Question

Question

This question was previously asked in

ALP CBT 2 Electrician Previous Paper: Held on 23 Jan 2019 Shift 1

Answer 1

There are two ways of expressing the efficiency of a secondary cell.

Ampere hour efficiency: It is the ratio of output ampere-hours to input ampere-hours of the cell.

Ampere hour efficiency, \({\eta _{Ah}} = \frac{{ampere\;hours\;provided\;on\;discharge}}{{ampere - hours\;of\;charge}} \times 100\)

The ampere-hour efficiency of a lead-acid cell is about 90%.

Watt-hour efficiency: It is the ratio of output energy to the input energy of the cell.

Watt-hour efficiency, \({\eta _{wh}} = \frac{{energy\;given\;on\;discharge}}{{energy\;input\;of\;charge}} \times 100\)

The watt-hour efficiency of a lead-acid cell varies between 70% to 80%.

Important point:

The efficiency of a lead-acid cell depends upon the following factors:

Rate of charge and discharge
Internal resistance and polarisation
The time interval between the end of discharge and the commencement of recharge.
Temperature