When the mains power is interrupted, the power supply time (i.e. backup time) of the power frequency UPS battery is not a fixed value, but is determined by multiple key factors, as follows:
1. Battery capacity (ampere hour, Ah)
This is the most direct factor affecting the power supply time. The larger the capacity of the battery, the more energy it can store, and theoretically, the longer the power supply time.
For example, under the same load, the power supply time of a 100Ah battery is usually longer than that of a 50Ah battery (assuming consistent battery voltage, type, etc.).
Attention: The actual capacity may be affected by temperature, aging degree, etc. (such as low temperature causing a decrease in capacity).
2. Load power size (W, W)
The power supply time is inversely proportional to the load power: the larger the load, the faster the energy consumption, and the shorter the backup time; Conversely, the longer it is.
Formula reference: Power supply time (hours) ≈ Total battery capacity (Wh) ÷ Load power (W)
(Note: Total battery capacity=battery voltage x capacity, for example, the total capacity of a 12V/100Ah battery is 1200Wh).
Example: A 1200Wh battery with a 600W load can provide power for approximately 2 hours; With a load of 1200W, it takes about 1 hour.
3. Number of batteries and series/parallel connection methods
Power frequency UPS typically requires multiple battery combinations to meet DC voltage requirements (such as 36V, 72V, 192V, etc.):
Series connection: Increase the total voltage (with constant capacity) to meet the requirements of UPS for DC input voltage, without directly increasing the power supply time.
Parallel connection: Increase the total capacity while keeping the voltage constant (for example, if two 100Ah batteries are connected in parallel, the total capacity will be 200Ah), extending the power supply time.
Therefore, under the same load, the more batteries are connected in parallel, the larger the total capacity, and the longer the backup time.
4. Degree of battery aging and health status
Batteries (especially lead-acid batteries) have a certain service life (usually 3-5 years), and as the number of charge and discharge cycles increases, the capacity will gradually decline:
The new battery capacity is close to the nominal value and the power supply time meets the standard;
Aging batteries may only have 50% or even lower capacity, significantly reducing power supply time.
In addition, long-term undercharging, overcharging, and high temperature environments can accelerate battery aging, further affecting backup time.
5. Environmental temperature
Batteries are temperature sensitive, and the optimal operating temperature for lead-acid batteries is around 25 ℃
When the temperature is below 25 ℃, the capacity decreases (such as when the capacity may only be 70% -80% at 0 ℃), and the power supply time is shortened;
Temperature above 25 ℃: Short term capacity may increase slightly, but it will accelerate battery aging, and in the long run, it will actually affect lifespan and capacity.
6. Conversion efficiency and self power consumption of UPS
In battery powered mode, there is energy loss (usually 80% -95% efficiency) when the inverter converts DC electrical energy into AC output for power frequency UPS, and the UPS itself also consumes a small amount of electrical energy.
The lower the efficiency, the greater the loss, and the less actual electrical energy available for the load, indirectly shortening the power supply time.
summarize
The power supply time of power frequency UPS batteries is the result of the combined effects of battery capacity, load power, battery status, environmental conditions, and other factors. In practical applications, it is necessary to calculate the required battery capacity based on the load demand and ensure that the backup time meets the standard through regular maintenance (such as detecting capacity and maintaining appropriate temperature).
