The extent of charge of lead accumulator is determined by

Step-by-step solution

In a fully charged lead accumulator or lead storage battery, sulphuric acid has a specific gravity (i.e., density that varies from 1.260 to 1.285. But during discharge (i.e., when the battery is in use). H ₂ SO ₄ is used up. array r Pb (s)+ PbO ₂(s)+4 H ⁺(a q)+2 SO ₄²⁻(a q) 2 PbSO ₄(l)+2 H ₂ O array As a result, the specific gravity of H ₂ SO ₄ falls when it falls below 1.230 the battery needs recharging.