Hydrogen

Methane

Oxygen

Carbon dioxide

1.25 V

1.50 V

1.00 V

2.00 V

lower e.m.f.

smaller quantity of electrolyte

higher internal resistance

compactness of the cell

its charge efficiency is low

it takes comparatively long time to charge a battery fully

in it, per cell charging voltage should not exceed 2.3 to 2.5 volts.

all the three problems stated above

36 No. in series

24 No. in series

18 No. in series

16 No. in series