the level of the electrolyte

the weight of the electrolyte

the specific gravity of the electrolyte

any one of the above stated parameter

lactometer

hydrometer

hygrometer

voltmeter

10 mm below the top of the plates

25 mm below the top of the plates

exactly at the top of the plates

10 to 15 mm above the top of the plates

1.2 V

1.5 V

1.8 V

2.0 V

40%

50%

60%

70%