Relationship between Battery Capacity and Discharge Rate

The capacity of a UPS battery refers to its energy storage capacity, representing the total amount of energy that a fully charged battery can release when discharged to a specified cut-off voltage. It is one of the most critical performance indicators for evaluating battery usability and service life.

According to the standard YD/T799-2002, the rated capacity of 2V, 6V, and 12V sealed lead-acid batteries is defined as the capacity obtained at a 10-hour discharge rate (I=0.1C₁₀A) under a standard temperature of 25℃. This specification clearly unifies the capacity calibration basis for 6V and 12V batteries under the 10-hour discharge rate.

However, in actual industrial applications, the industry has formed relatively stable customary practices. At present, most mainstream manufacturers follow such a calibration principle: the capacity of 2V batteries is marked based on the 10-hour discharge rate (I=0.1C₁₀A), while the nominal capacity of 6V and 12V batteries is mostly based on the 20-hour discharge rate (I=0.05C₂₀A).

This difference in discharge rate standards directly affects the actual available capacity of batteries in practical use. Generally speaking, the faster the discharge rate, the lower the actual available capacity; conversely, a slower discharge rate will bring a relatively higher displayed capacity. Therefore, when selecting and matching UPS batteries, users and engineers must fully consider the actual discharge rate requirements of the system to avoid deviations between nominal capacity and actual working performance.