Correct Answer - Option 3 : WH efficiency
Efficiency of Battery: There are two ways of expressing the efficiency of a secondary cell viz
(i) Ampere hour efficiency
(ii) Watt-hour efficiency
(i) Ampere-hour Efficiency (ηAh): It is the ratio of output ampere-hours to the input ampere-hours of the cell i.e.
\(\eta_{Ah}=\frac{I_dT_d}{I_cT_c}\)
Where, IdTd is Ampere-hours provided on discharge
IcTc is Ampere hours of charge
Note that efficiency is considered for a complete charge and complete discharge down to the state in which the cell was at the commencement.
(ii) Watt-hour (Wh) efficiency (ηWh): It is the ratio of output discharging energy to the input charging energy of the cell i.e
\(\eta_{Wh}=\frac{V_dI_dT_d}{V_cI_cT_c}\)
Where, VdIdTd is the energy obtained from a battery while discharging
VcIcTc is the energy obtained from a battery while charging
Again, efficiency is considered for a complete charge and complete discharge down to the state in which the cell was at the commencement.