Care of lead cells
The level of the sulphuric acid in a lead cell should be inspected regularly and any loss from evaporation made up with distilled water only. Acid should never be added except in rare cases where spillage has occurred. Lead cells must be charged
regularly, using the maker’s recommended charging current, and not left standing for any length of time in a discharged condition. When not in use, they should be given a “topping up” charge at least once a month. When fully charged, hydrogen is freely evolved from the negative plates and oxygen from the positive. This is called “gassing”. Needless to say, cells on charge should never be examined in the light from a naked flame, as a mixture of hydrogen and oxygen is dangerously explosive. Over-discharging and “shorting”, i.e., connecting a wire directly across the terminals are very detrimental. Such treatment causes swelling and buckling of the plates, with the result that the active material becomes loosened and falls to the ·bottom as a sludge. Under these conditions, and particularly if the cell is left in a discharged condition, the lead sulphate in the plates changes to a white crystalline
form which cannot be reconverted into leaduv) oxide and lead respectively. Once this has occurred the cell is said to be “sulphated”, and for this there is no remedy except to renew the plates.