Understanding how to calculate the UPS autonomy This is essential for choosing and adapting this device to your needs. This is because this value indicates how long the protected equipment will remain active in the event of power outages, for example.

To help, we’ve prepared this practical guide containing simple steps on how to perform this calculation accurately. Check it out!

So, what exactly is UPS autonomy?

THE UPS autonomy This refers to the minimum time during which a UPS, with fully charged batteries, ensures continuous power to the load when a power outage occurs in the commercial electrical grid. In short, it is the period during which connected devices can continue to function using the UPS’s power supply, if available. power outage.

Calculating the UPS (Uninterruptible Power Supply) runtime is important because it determines the uptime of devices if the power supply is interrupted. This is especially critical in sensitive environments, data centers, hospitals, and communication systems, where business continuity is essential. This calculation aids in planning and decision-making in case the commercial power supply is not restored.

The autonomy calculation considers several factors, including the UPS battery capacity (Ah), the total power of the connected devices, and finally, the efficiency of the power conversion system. Based on this data, the approximate time that the equipment will continue to function before the battery runs out is determined.

Adequate autonomy helps prevent data loss, workflow interruptions, and damage to sensitive devices. This allows time to safely shut down systems and also save important data.

What factors determine the autonomy time?

The runtime of a system protected by an uninterruptible power supply (UPS) is determined by several interrelated factors. Among them:

  • Battery bank capacity – The greater the capacity of the battery or battery pack, the more energy is stored and supplied to the devices. Batteries with higher capacity (Ah) generally offer longer runtime.
  • Power of Connected Equipment – The total power consumption of the equipment (computers, servers, devices, etc.) connected to the UPS can affect its runtime. Equipment with higher power consumption will have less runtime compared to devices with lower consumption.
  • Applied load – In other words, how much of the supplied energy the devices are consuming affects the battery discharge rate. Generally, UPS (Uninterruptible Power Supply) autonomy is designed for full load operation, meaning that 100% of the power delivered by the UPS is consumed by the load. When the load does not fully utilize the power provided by the UPS, an increase in autonomy is observed in practice.
  • Battery age –Over time, a battery’s capacity can decrease due to natural wear and tear; that is, even under the same operating conditions, older batteries may not provide the same range as new batteries.
  • Charge and discharge cycle – The number of times a battery has been discharged and recharged over time can affect its ability to hold a charge. Therefore, its range will be affected. If the time intervals between power outages are insufficient to fully recharge the battery, future ranges will be reduced.

Types of Batteries

There are several types of batteries on the market. In uninterruptible power supply (UPS) systems, for example, VRLA (lead-acid), lithium-ion, and alkaline batteries are the most common. To choose between each type of battery, one must consider that each one presents differences in terms of charging regimes and… lifespan which significantly impact the availability, price, and volume they occupy in the installation.

Steps to calculate UPS runtime.

Calculating the UPS (Uninterruptible Power Supply) runtime allows you to determine how long connected devices can operate in the event of a power outage. This calculation can be done using the constant current discharge method or the constant power discharge method. Because it is a more accurate method and better suited to UPS applications, we have listed below the basic steps to perform this calculation using the constant power discharge method:

  1. Identifying Connected Equipment – List all the equipment and the power rating (usually in Watts) of each load you intend to protect with the UPS. This value can be found on the device labels or in each device’s manual.
  2. Calculate the Total Power: Add up the power ratings of all the devices to get the total power in Watts (W). This value will indicate the total load that the UPS will need to supply.
  3. Consult the battery’s technical specifications. Battery manuals and catalogs typically provide information on performance in both constant current and constant power discharge methods. This information is available at various voltage levels, with 10.2V or 10.5V being common levels for batteries in uninterruptible power supply (UPS) applications.
  4. Calculate Theoretical Autonomy – Given the total wattage and the total number of batteries used, calculate the power supplied by each battery using the formula: Power per battery = total power / (number of batteries x inverter efficiency). Uninterruptible power supplies (UPS) are high-efficiency devices. However, some energy will be lost in the process of converting direct current (DC) to alternating current (AC). Although it is a small loss relative to the load, this is information to be considered in the calculation for a more accurate autonomy result.
  5. Consult the Technical Specifications for the batteries. Identify the battery performance using the constant power discharge table. This table provides several cutoff voltage levels (or end-of-range voltage) in the rows and the range in relation to the power supplied by the battery for a given cutoff voltage level in the columns. From the calculated battery power, find the equivalent power considering the battery cutoff voltage. The intersection of row and column leads to the projected battery range for the specified power.
  6. Consider Battery Aging: If the battery is not new, you may experience a reduction in the battery’s actual capacity due to aging.

Relationship between UPS autonomy and battery management

WCalculate the UPS autonomy This contributes to the management of the operation supported by the UPS. This is also especially useful for evaluating the performance of the batteries in use in the installation. If the actual runtime is significantly lower than the calculated runtime, this will indicate the need to evaluate or replace the batteries due to natural wear and tear.

Modern uninterruptible power supplies (UPS) feature advanced individual battery monitoring systems. If necessary, they notify the user when a battery needs replacing. specific batteries. Furthermore, UPS systems also program self-tests and have communication features that provide real-time information, via display or monitoring software, on the UPS’s autonomy. This can greatly simplify the lives of power system managers.

Remember that when calculating UPS runtime, you will have a rough estimate of the minimum protection time for the loads. Due to the factors already explained, the actual runtime results may vary. Therefore, it is advisable to check the UPS’s technical specifications. Additionally, it is necessary to consult the UPS manufacturer for precise information on expected runtime in different scenarios.

It is worth highlighting that the flexibility and innovation of Engetron’s uninterruptible power supplies (UPS) allow for extended runtime. This ensures greater security and durability in the power supply for equipment.

For more information, Contact us And talk to an energy systems specialist at Engetron!