Cell and Battery Voltage

External load Electrolyte Porous separator Negative electrode Positive electrode BATTERY COMPONENTS AND OPERATION DOE-HDBK-1084-95 Lead-Acid Storage Batteries Batteries Page 6 Rev. 0 Figure 1. Major components of a cell. by cell type. Materials used as separators must allow ion transfer between the electrolyte and electrodes. Many separators are made of a porous plastic or glass fiber material. The above components are housed in a container commonly called a jar or container. Cell and Battery Voltage In order for a cell or battery to be able to deliver electrical current to an external circuit, a potential difference must exist between the positive and negative electrodes. The potential difference (usually measured in volts) is commonly referred to as the voltage of the cell or battery. A single lead-acid cell can develop a maximum potential difference of about 2 V under load. A completely discharged lead-acid cell has a potential difference of about 1.75 V, depending on the rate of discharge. Capacity and Battery Ratings In general terms, the capacity of a cell/battery is the amount of charge available expressed in ampere-hours (Ah). An ampere is the unit of measurement used for electrical current and is defined as a coulomb of charge passing through an electrical conductor in one second. The capacity of a cell or battery is related to the quantity of active materials in it, and the amount of electrolyte and the surface area of the plates. The capacity of a battery/cell is measured by discharging at a constant current until it reaches its terminal voltage (usually about 1.75 volts). This is usually done at a constant temperature, under standard conditions of 25ºC