When a battery is being discharged the lead active material on the plates will react with the sulfate from the electrolyte forming a lead sulfate on the plates. During recharge, the lead sulfate is reconverted into lead active material and the sulfate returned to the electrolyte. If a battery is left in a discharged condition or is not properly recharged on a regular basis, the lead sulfate will become hard and have a high electrical resistance. This is what is normally called a sulfated battery. The lead sulfate may become so hard that normal recharge is unable to break down the lead sulfate crystals, rendering the battery near useless.