![]() It is important that there is plenty of room underneath the plates to catch this shed material. This causes the plates to gradually shed the paste during their life. One of the problems with the plates in a lead-acid battery is that the plates change size as the battery charges and discharges, the plates increasing in size as the active material absorbs sulfate from the acid during discharge, and decreasing as they give up the sulfate during charging. The positive plates gradually turn the chocolate brown colour of lead dioxide, and the negative turn the slate gray of 'spongy' lead. After the acid has been added to the cell, the cell is given its first forming charge. Each alternate plate is connected together. An odd number of plates is usually used, with one more negative plate than positive. Once dry, the plates are then stacked together with suitable separators and inserted in the battery container. At this stage the positive and negative plates are similar, however expanders and additives vary their internal chemistry to assist in operation when in use. This porous paste allows the acid to react with the lead inside the plate, increasing the surface area many fold. ![]() The paste is pressed into the holes in the plates which are slightly tapered on both sides to assist in retention of the paste. (Different manufacturers have modified the mixture). ![]() The holes of the grid are filled with a mixture of red lead and 33% dilute sulfuric acid. Each plate consists of a rectangular lead grid alloyed with antimony or calcium to improve the mechanical characteristics. The Faure pasted-plate construction is typical of automotive batteries. Planté's method of producing the plates has been largely unchanged and is still used in stationary applications. Gaston Planté realised that a plate construction was required that gave a much larger effective surface area. However such a construction would only produce around an amp for roughly postcard sized plates, and it would not produce such a current for more than a few minutes. The principle of the lead acid cell can be demonstrated with simple sheet lead plates for the two electrodes. was regularly measured and written on a blackboard in the control room to apprise the commander as to how much underwater endurance the boat had remaining. When used in diesel-electric submarines, the S.G. Some battery designs, such as those used in electronic flash units, have a simple hydrometer built in using coloured floating balls of differing density. It is relatively simple to determine the state of charge by merely measuring the specific gravity (S.G.) of the electrolyte, the S.G. After full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V.īecause the electrolyte takes part in the charge-discharge reaction, this battery has one major advantage over other chemistries. ![]()
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