Reading Multiple Capacity Ratings for One Model: 20, 10 and 5 Hour Rates
Turning through a lead-acid battery specification table, one model often carries several capacity figures: nominal capacity (Ah) at the 20-hour rate, at the 10-hour rate and at the 5-hour rate, and some tables also list the 30-minute rate, 2-hour rate, 8-hour rate and 1-hour rate, together with rated power (W/cell) at the 15-minute rate. These numbers do not contradict one another; they are results measured on the same battery under different discharge conditions.
The hour rate preceding a capacity rating describes the length of the discharge. The 20-hour rate means the battery is discharged to the end voltage over a longer period, and the 10-hour and 5-hour rates shorten that period in turn. For the same model, the capacity released over a shorter discharge time is usually smaller, which is why the table lists them separately for systems with different backup durations. When reading the table, checking which hour rate follows the figure matters more than the size of the figure itself.
Matching a capacity figure to a backup duration is the most practical step in selection. If the system states its load and backup requirement at the 20-hour rate, check the nominal capacity (Ah) at the 20-hour rate; if the backup time is designed at 10 hours or 5 hours, read the 10-hour and 5-hour rate capacities respectively. For duties such as UPS that must supply backup over a short period, the table may also give the 30-minute, 2-hour and 1-hour rate capacities, and rated power expressed in W/cell at the 15-minute rate, which correspond to even shorter discharge times.
Which figure to read at ordering depends on the backup duration the system actually needs, not on the largest number in the table. When checking a model, confirm the model, the voltage and the capacity item for the required hour rate together, and also check whether parameters such as weight (kg), standard terminal type and optional terminal type suit the installation conditions. Where the table lists several hour rates, circling the required one before comparing avoids covering a 5-hour design requirement with a 20-hour figure.
It should be noted that capacity items at different hour rates are parallel specification data, each corresponding to its own discharge condition, and cannot be converted into or substituted for one another. B.B. Battery was founded in 1992 and operates a production base in the Changsha XingSha National Economic and Technological Development Zone, Hunan Province, commissioned in 2006, with about 60,000 square metres of plant. Reading the specification table item by item against the hour rate is the basic method by which buyers and engineers can read capacity ratings clearly.
