C/10 rate (amperes)200 Ah/10 h20 amperes.Lead-Acid Storage BatteriesDOE-HDBK-1084-95BATTERY COMPONENTSAND OPERATIONRev. 0Page 7Batteries(1)(77ºF). The capacity is calculated by multiplying the discharge current value by the timerequired to reach terminal voltage.The most common term used to describe a battery's ability to deliver current is its ratedcapacity. Manufacturers frequently specify the rated capacity of their batteries in ampere-hours at a specific discharge rate. For example, this means that a lead-acid battery rated for200 Ah (for a 10-hour rate) will deliver 20 amperes of current for 10 hours under standardtemperature conditions (25ºC or 77ºF). Alternatively, a discharge rate may be specified byits charge rate or C-rate, which is expressed as a multiple of the rated capacity of the cell orbattery. For example, a battery may have a rating of 200 Ah at a C/10 discharge rate. Thedischarge rate is determined by the equation below:Battery capacity varies with the discharge rate. The higher the discharge rate, the lower thecell capacity. Lower discharge rates result in higher capacity. Manufacturer's literature onbatteries will normally specify several discharge rates (in amperes) along with the associateddischarge time (in hours). The capacity of the battery for each of these various dischargerates can be calculated as discussed above.The rated capacity for lead-acid batteries is usually specified at the 8-, 10-, or 20-hour rates(C/8, C/10, C/20). UPS batteries are rated at 8-hour capacities and telecommunicationsbatteries are rated at 10-hour capacities.SeriesandParallelConnectionsCells and batteries may be connected in series, parallel, or combinations of both. Cells orbatteries connected in series have the positive terminal of one cell or battery connected tothe negative terminal of another cell or battery. This has the effect of increasing the overallvoltage but the overall capacity remains the same. For example, the 12-V lead-acidautomobile battery contains 6 cells connected in series with each cell having a potentialdifference of about 2 V. Another example of cells or batteries connected in series is shownin Figure 2.Cells or batteries connected in parallel have their like terminals connected together. Theoverall voltage remains the same but the capacity is increased. For example, if two 12-Vautomotive batteries were connected in parallel, the overall voltage for the batteries wouldstill be 12 V. However, the connected batteries would have twice the capacity of a single12-V battery. Another example of cells or batteries connected in parallel is shown inFigure 3.

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