aircraft resources
...n a steel container, which is the positive terminal an insulator is pressed over this cell. Very thin corrugated zinc is saturated with an electrolyte solution of potassium hydroxide when placed over the insulator. A steel cup encloses the cell then touches the zinc and becomes the negative terminal. Secondary cells are cells that do not produce electrical energy. They store it in chemical form. Batteries consisting of secondary cells are called storage batteries. Lead Acid Battery Lead acid batteries are used mostly as storage batteries in an aircraft. They are made up of either six or twelve cells. Each cell produces about 2.1 volts. They consist of positive and negative plates. The positive plates are made of a grid of lead and antimony filled with lead peroxide. The negative plates use the same grid of lead but are filled with spongy lead. Positive plates are joined and placed between piles of negative plates. Porous separators keep the plates apart and hold electrolyte of sulfuric acid and water in contact with the active material. The chemical change that occurs in this battery during discharge is when electrons leave the negative plates and positive ions form and attract negative sulfate ions from the sulfuric acid in the electrolyte therefore, the combo of the two elements create lead sulfate on the negative plates. The chemical change during charging occurs when the positive plates are connected to the positive terminal. Electrons are then drawn from the positive plates and are forced on the negative plates. Electrons on the negative plates drive the negative sulfate ions out of the lead sulfate back to the electrolyte. The sulfate ions then join with hydrogen to form sulfuric acid. To test a battery, you have to check its specific gravity, and that is checked with a hydrometer. A hydrometer measures the depth a calibrated float sinks in a sample of electrolyte sucked into it. A standard of 80° is used as the electrolyte temperature reference. If it is any other temperature, you must make a correction to the hydrometer reading. The electrolyte is less dense at higher temperatures and denser at lower temperatures. The specific gravity of a lead-acid battery that has 2.10 volts per cell is li275. The capacity of a battery s affected by four things: the amount of active material, plate area, quantity of electrolyte, and the temperature. Capacity is measured in ampere-hours with one ampere-hour equaling the amount of electricity that is put into or taken from a battery when a current of one ampere flows for one hour. Servicing and Charging The most important part of servicing a battery is keeping the battery clean and all the terminals tight and corrosion free. You can remove any corrosion by scrubbing the battery box and the top of the battery with a soft bristle brush and a solution of sodium bicarbonate (baking soda) and water. Avoid getting any baking soda in the cells since it neutralizes the electrolyte. Rinse clean with water and d...