You need to understand all the specifications of your Uninterruptible Power Supply (UPS) system so you can get the best out of it. Among the most important specs to master is the duration the UPS can last. Knowing when your unit will hit the cut-off voltage simplifies the planning process and makes everything exciting.
This article teaches you how to estimate the number of hours your UPS backup can last on full charge. You will also learn the factors influencing the duration of your UPS's operation and how to boost its longevity.
First: Some UPS Basics, Including The Duration of Operation
UPS systems provide electrical power to our appliances when an interruption occurs on the utility grid. To operate, a UPS has a battery and an inverter. The battery receives and stores energy when the utility grid has power. But in the event of an outage, the inverter converts the energy in the battery to AC power, which then runs your appliances during the outage.
Each battery type has a particular cut-off voltage depending on the technology and chemistry powering it. A cut-off voltage is the minimum voltage below which the UPS automatically shuts down. It ensures that the running load does not overdrain the battery.
You don’t want to excessively discharge your battery because that would considerably shorten its lifespan. Therefore, the duration of operation of your UPS is the time it can take to support an electrical load before reaching the cut-off voltage and shutting down.
What Factors Influence UPS Duration?
Several factors can lengthen or shorten the duration of a UPS system. We recommend knowing and understanding each so you may adjust accordingly to give your power backup system more years and increase its performance. Here are the four primary factors that dictate the duration of your UPS system.
The Load Capacity
The load capacity is the total load of your electrical devices connected to the UPS system. We measure load capacity in Watts (W) and can get the value by adding the power ratings of the individual appliances the UPS supplies to power to. Let’s look at an example to demonstrate how you can easily estimate the load capacity in your house, office, or anywhere you’re using or intend to use a power backup unit.
Given you have the following appliances and their corresponding power ratings in Watts;
|
Appliance |
Power Rating (Watts) |
|
Refrigerator |
110 |
|
5 Light Bulbs (10w each) |
50 |
|
Tv Set |
100 |
|
Desktop Computer |
150 |
|
Music System |
80 |
You can get the load capacity by summing up all the above power ratings.
Therefore, Load Capacity = (110+50+100+150+80) = 490w.
Generally, a high load capacity shortens the run-time of a UPS system because higher loads mean a lot of energy is pulled from the battery at any given time. So, a household or office setting with a load capacity of 700w will experience a shorter operation duration than one with a 490w load, and vice versa.
When it comes to longevity, a UPS unit that always runs at high load capacities close to its maximum capacity tends to degrade quickly. This is because the system does more work at a high load capacity than a lower one. So, still using the above example, the 700w load configuration would shorten the lifespan of a UPS system more than the 490w capacity.
To grant your UPS unit longer operation time and an extended lifespan, you will want to try to keep the load capacity down. In other words, we’re saying you should not strive to hit the maximum load capacity. Operating at around 50 to 60% of the total load capacity of your UPS should just be fine.
Battery Condition
The battery condition will directly influence the duration a 1000VA UPS system lasts. This is because the battery is the source or the storage bank of the energy running the UPS unit. So, a healthy battery will automatically lead to longer operation durations due to excellent performance.
Your UPS won’t serve you long enough if it is not in the right environment. That means the installation spot should not be too cold or extremely hot. While Lithium Iron Phosphate (LiFePO4) batteries usually perform optimally in a wider range of temperatures than their Lead-acid counterparts, their performance lags significantly when the temperature hits the extremes. Operating under extreme temperatures, therefore, makes a UPS run for fewer hours than it should.
Maintaining the battery’s health also means performing routine maintenance practices such as cleaning dirty terminals or adjusting the electrolyte levels if your UPS uses traditional Lead-acid accumulators. Besides achieving impressive operation durations, ensuring the UPS runs under conducive environmental conditions increases its lifespan and cuts long-term costs.
So, if you check your UPS battery regularly and fix any emerging abnormalities, your backup will always last longer. Installing the system at a spot with ideal environmental conditions and replacing faulty batteries also optimizes the runtime significantly and lets you enjoy more power.
The Power Consumption of Connected Devices
The power consumption characteristics of the appliances you use also influence the runtime of the UPS system. There are those devices that pull a lot of power and ones that utilise smaller amounts.
Generally, as the power consumption increases, the UPS unit’s runtime decreases significantly. This is because devices that suck in a lot of power deplete the battery faster, thus shortening the operation duration.
Connecting several devices that consume much energy to a UPS system also makes it work extremely hard. Unfortunately, your system’s lifespan will decrease if it strains most of the time to carry your high electrical load. That means the battery can barely hit 5 years if your UPS uses a Lead-acid battery. On the other hand, a Lithium-based UPS system may struggle to reach its average lifespan of about 10 years.
We’ve compiled a list of some electrical appliances and their average power consumption rates in Watts (W). Kindly note that the actual rating will depend on the brand and model of a given device.
Network Router - 15
Laser Printer - 400
Photocopier - 350
Refrigerator - 400
LED TV - 100
Server - 700
Microwave Oven - 700
Washing Machine - 600
Efficiency & Age of The UPS
A UPS system with top-notch efficiency wastes minimal energy as it operates, which converts into a lengthy operation duration. A high efficiency also means that your UPS spends a smaller portion of the power it generates to run its internal systems such as the battery management module and the cooling mechanism.
The age factor also comes in because the efficiency of most electrical systems always drops as they get older. Besides lowering efficiency, the UPS battery weakens as its age increases, which results in a smaller capacity to store electrical energy. So, what follows is a power system that doesn’t run long enough.
Now it's correct to say that the higher the efficiency of a UPS, the longer it can run before hitting the cut-off voltage. Also, newer and well-maintained UPS units exhibit excellent performance, thereby granting you more hours of consistent power. This underscores the significance of always replacing your aged UPS systems with newer and more advanced models like the ones available on the market today.
Estimating The Runtime of a 1000VA UPS
To understand the estimation method we’ve used in this section, it’s crucial to know what the value “1000VA” means. Well, 1000VA can also be expressed as 1000 Watts, and it’s the maximum possible amount of power this UPS can avail for use at a given instance.
Calculating the runtime of a UPS system begins by knowing the system’s battery specifications. In this case, we’ll use a 24v, 300Ah battery.
Runtime = (Total Battery Capacity in Watt Hours (Wh)/Total Load In Watts (W)).
Assuming an 80% (0.8) efficiency for the battery;
Total Battery Capacity = {Efficiency * Voltage (v) * Current (Ah)} = 0.8*24*300 = 5760Wh
Runtime at 30 % Load Capacity (Low Load)
Assuming the UPS has 100% efficiency;
Load = 0.3*1000w = 300w
Runtime = (Battery Capacity(Wh)/Load (w)) = (5760/300) = Approximately 19 hours
Runtime at 50% Load Capacity (Medium Load)
Load = 0.5*1000w = 500w
Runtime = (Battery Capacity(Wh)/Load (w)) = (5760/500) = Approximately 11.5 hours
Runtime at 70% Load Capacity (High Load)
Load = 0.7*1000w = 700w
Runtime = (Battery Capacity(Wh)/Load (w)) = (5760/700) = Approximately 8 hours
So, from the above three different load scenarios, you can see that an increase in the Load your UPS operates decreases its runtime, and vice versa.
Practical Consideration
The two most reliable ways to achieve the best experience with a UPS system is to maintain it regularly. You should also know when to replace the whole unit with a new one, or how to upgrade it to meet emerging power needs.
To ensure your UPS battery is safe and always running optimally, you should check it regularly to identify any problems and fix them before they worsen. Maintaining healthy depths of discharge, keeping charging within safe limits, and not overloading the UPS make it durable.
We also recommend paying attention to your UPS unit’s behavior and acting accordingly. Abnormally shorter runtimes or consistent failures might be signs your system requires a replacement with a new one. But that’s not all. You should consider a replacement if the unit has operated for long, advisably, after an average of about 5 years or slightly more.
When it’s time to upgrade, go for UPS systems with modular design to enhance scalability. Also, look for a unit that can handle higher loads. Anything between 1500VA and 2500VA should be okay. Then most importantly, the UPS battery should have a higher capacity (200Ah to 300Ah) for extended backup capabilities.
What We’ve Covered
The runtime of a 1000VA UPS depends on several factors. For example, it increases when the total load is low, and your UPS is new and running optimally. Also, a larger UPS battery capacity increases the runtime significantly.
Extending the lifespan of a UPS battery requires not overcharging or excessively discharging it. You should also clean the terminals regularly. Notably, UPS systems with modular design, higher battery storage, and high load capacity are ideal when replacing your current unit. Always make the correct considerations for decent results.
