UPS Basics

UPS Knowledgebase

UPS Basics

The following UPS Basics should help every new-comer to the UPS-World to better understand  the whys and how’s of the UPS. Here you can find general UPS questions that could help you decide what kind of UPS you need!

Brand Information

BlueWalker GmbH is a german company with more than 15 years of experience in the EMEA market. The name has been popularized in the german speaking countries.

PowerWalker is BlueWalker´s brand for professional solutions in uninterruptable power supplies. In all other countries, the brand PowerWalker has made its own name.

The PowerWalker logo is a flywheel. A device used to convert kinetic energy into a standby supply of DC power, usually used in huge industry facilities. The phylosophy behind it is to always stay in motion, always keep walking.

Our PowerWalker brand is focused on the reliability and quality of the UPS products at an excellent price-performance for our customers.

Due to our size, we are much closer to our customers and therefore better able to provide individual and targeted solutions. We offer a wide range of products, and we attend and support are customers with an in-house service hotline.

We continuously update our existing models and improve what we have to grow and develop with the market and our customers.

General UPS Information

For the technical explanation please visit our Lexicon. Off-Line UPS are designed for small load uses.


• Installation is easy and quick

• Low costs for less critical loads

• Silent (no fans for cooling)

• Small own power consumption

• Compact UPS


Usually they produce a simulated sine wave

Transfer times are not seamless

Loads will receive unfiltered voltage

Application scope: Home, Office and Stores.

For the technical explanation please visit our Lexicon. Line-Interactive UPS are designed for medium cost application with moderate load levels.


• Higher protection with more functions

• Cost-effective solution

• Mostly silent. Fans work when not in Normal Mode

Pure Sine Wave is an option (depends on the model)

Some accessories are available (depends on the model)

Protection against voltage fluctuations 


There are still some small transfer times

There is no protection against transients

There is no frequency correction or adjustment

Application scope: Home, Office, Stores and IT & Data Solutions.

For the technical explanation please visit our Lexicon. On-Line UPS are designed for mission-critical loads.


• Double-conversion, always a clean output

• For high-power demand and for sensitive equipment

• Pure Sine Wave under all conditions

• Frequency can be adjusted if desired

• Zero transfer times in standard operations

• Many accessories are available (depends on the model)


• Fans are always on

• This products require space and technical knowledge

• High own power consumption

• High investment

Application scope: Stores, IT & Data Solutions, Medical Equipment, Entertainment, Emergency Situations, and Industrie & Construction.

Interruptions: Also known as a blackout, a complete interruption of the electrical supply. Depending on the duration, an interruption can be instantaneous, momentary, temporary, or sustained.

Voltage fluctuations: Overvoltage and undervoltage are the most commonly known. They are both a prolonged sag and swell respectively. Sags and undervoltage are both a reduction of the AC voltage in a given time. Swells and overvoltage are both an increase of the AC voltage in the circuit.

Transients: The most damaging electrical disturbances. An impusilve transient is a sudden peak, commonly known as surge or spike. An oscillatory transient, just like the name, will swell and shrink in a oscillatory form (like a lie-detector).

Common consequences are damage to electrical components, system halt or shutdown, reduced product-life, overheating, flickering, communication interference, or complete loss of data and hardware.

To get the ideal UPS product we recommend the customer to answer the following questions:

• What kind of electrical disturbances do you want to prevent? What kind of electrical disturbances do you want to protect your devices from? Depending on this, we will recommend different UPS technologies. Each technology supresses diferrent disturbances in the incoming power supply (see electrical disturbances).

• Where is the UPS going to be? In a household, at the office, in a closed-server room or at a building site? This also helps when deciding the correct technology.

• Which electrical components do you want to protect? Do you know the approximate load size in kVA?  This will define how small or big the UPS capacity should be. Please also consider in-rush currents and the characteristic of the load (inductive or capacitive).

• Do you require back-up time? If you require long back-up times, a UPS with the possibility of battery packs or EBM should be important. This will help to define how much extra back-up time the UPS should provide the critical loads.

• And last but no least. Do you require extra or specific features? Special communication, monitoring or managing.

• UPS’s electronics are designed to work for many years. Correct preventive maintenance and optimal operating condition will additionally extend this time.

• If UPS is equipped with fans, please consider that the design life of this rotating component is 5 years.

• If UPS is equipped with dust filter, please consider to check and replace it as soon as it is blocked with “schmutz”.

Please make sure that UPS is operating in allowed environment. Limits may very depending on model, but safe conditions include:

• 0°C – 40°C (for long battery life, keep the UPS at an ambient temperature of 25°C)

• 20% – 80% relative humidity without condensation

• No standing or running water in the vicinity

• No exposure to direct sunshine or heating equipment

• Appropriate electrical input TN-S 230V grounded

• Secure enough space for air circulation; never cover the cooling vents or fans

• Equipment is exlusively for indoor use! IP rating of 20!

UPS is designed to operate maintenance free. Nevertheless, certain steps will extend its life time! We recommend the following:

• Regularly check if the unit’s operating environment is still within the recommended conditions

• For the best preventive maintenance, keep the area around the UPS clean and dust-free. If the atmosphere is very dusty, clean the outside of the UPS with a vacuum cleaner

• Unplug the UPS prior to cleaning and do not use liquid or spray detergent

Use dry soft clothes to clean the front panel and plastic parts. Take special care for the air inlets for the fans proper funcitioning

• To maintain optimal battery charge, leave the UPS plugged into an AC outlet at all times

• The design life of the battery is 3-5 years counted from the date of production of the battery, which means that effective service time counted from the date of purchase/installation can be shorter. After two years it is recommended to strictly and frequently (e.g. once every three months) monitor the battery condition. If the discharging time of fully charged batteries is less than 50% of the rated value, then the batteries need to be replaced

• There are many factors that can affect the amount of power that your computer system requires. To secure sufficient safety margin in case of sudden consumption peaks, please keep the casual load approximately about 75%,  of the unit’s rated capacity (the system will work more stable)

• Considering internal own power consumption of the UPS, please keep the casual load on the UPS above 25% for optimal system performance. If your load is smaller, consider choosing a smaller unit with smaller own power consumption for energy saving

It depends on the size of the UPS. In every datasheet the maxium capacity is given in watt and VA. Most devices like PC’s, printers, etc, show watt usage/consumption. When selecting appropriate UPS for your load, you need to consider not only nominal power consumption but also maximum power consumption, peaks, in-rush currents and even harmonic distortions. On top of that a safety margin is advised.

We suggest not to connect more than 75% of the nominal watt power capacity of the UPS.

• Make sure the battery is fully charged before the UPS is stored

• Turn off the UPS and disconnect its power cord from the wall outlet. Disconnect all output cables

• The UPS should be stored in a cool dry location

• For extended storage in moderate climates, the battery should be charged for several hours every three months by plugging the UPS to the power socket. Repeat it every two months in high-temperature locations

• For extended storage, we recommend covering the UPS to protect it against the dust or preferably to pack into original foil, cushions and box

• Please transport the UPS only in the original package to protect against shock and impact

• Front panel (the buttons) should be protected against accidental turning on the unit

• A hazardous voltage still may be supplied from the battery and the unit may heat up in the box. Where available, disconnect the batteries for the transportation

Typical power strip is rated to 3000-4000VA, while a small home UPS could be 650-2200VA. If the power strip is connected with enough devices and electrical equipment, the capacity of the UPS would be already exceeded. If really required, we can only recommend that the total VA does not exceed what the UPS can deliver.

An additional hint or recommendation would be to connect the UPS to the power strip and not the way around. Typical power strips already have a higher surge protection as the UPS, and are way cheaper. This way, the power strip will protect the UPS first, and then the UPS the connected critical loads.

Nevertheless, it would function, so there is no serious danger considered.

It depends on the UPS technology. For Off-Line UPS it is unaffordable to back-up such inrush current. The UPS will go into Fault Mode and shutdown immediately (unless the UPS is already oversized). For Line-Interactive, it applies the same, unless the waveform is pure sine wave. Because all On-Line models deliver pure sine wave, they can also work with APFC with no problem.

Warranty period for the device: 24 months
Warranty period for solar inverters (including ESS): 60 months

For additional information: Terms and Conditions for the PowerWalker Warranty

Battery Information

The typical lifespan of a UPS battery is 3-5 years from the start of production. However battery life can vary greatly depending on environmental conditions and amount of discharge cycles. For instance, battery life decreases if the UPS is operated under a high temperature environment or is frequently discharged.

Please remember that the life of the battery starts at the time of production (not at the time of first usage).

A battery must be recharged every 3 months in storage (20°C), otherwise it will deplete its capacity. Cold and dry would be the optimal storage environment (<20°C). In a very hot and humid environment (20°C-40°C), it is recommended to recharge them every 1-2 months.

When a client is looking for a UPS to safeguard his load with a determined back-up time, it always comes to the an end decision, to buy a small UPS with an additional Battery Pack or to just buy a bigger UPS. Because of the price difference (UPS + BP > Bigger UPS) the customer normally decides to pay less for a bigger UPS then to pay more and have the ideal solution of a UPS with an additional BP.

The UPS with a Battery Pack may look like the expensive option, but bigger UPS have a higher power consumption, meaning that over its lifetime having a bigger UPS will result in a higher electric bill.

One of the most critical rules in UPS maintenance and safety is performing a regular battery test. Our software offers a scheduling function for this task. If batteries are not checked regularly following situations may happen:

• Battery capacity will decrease over time and reach a point where it cannot support the load long enough. It might even render the UPS unusable.

• Continuous charging of faulty batteries may lead to leaks, swelling or even burning of the battery.

Basic Battery Test

The software will perform a 10 second battery test. Please note that the test only proves that the battery will hold the connected load for 10 seconds. Hence, the test will only determine if the battery is not depleted. We recommend the basic test at least once a month.

Real Life Test

Since the typical expected backup time is much longer than 10 seconds, we recommend a real life test to ensure the proper functionality of the UPS system.

Please cut off the input (i.e. by switching the input breaker or unplugging the input cable) and measure how long the UPS can backup the load. Knowing the load in watts (you can read it in the monitoring software), you can compare it with the real performance. Feel free to contact our support team if you need a recommendation. This will give you the best overview of the batteries condition.

You can also monitor the backup time changing over the lifespan of the batteries. If it drops below your requirement, please change the batteries. We recommend to perform the real life test with the following schedule:

  • At the very beginning of any operation
  • Every 6 months in the first 2 years
  • Every 3 months after 2 years

To assess the battery condition you need to check the battery voltage. If opening the UPS and measuring the voltage with a multimeter is not possible, you can use the in-software provided measurement tool.

Please avoid misinterpreting the reading: When the UPS is charging, it will apply a charging voltage approx. of 13.7 VDC to the battery and it will try to boost the battery voltage to this value. If the charger is active, the software wont read the battery voltage, instead it will read the charger voltage. To avoid this, you need to switch into battery mode (simulate a mains failure). Without AC input, the charger will switch off and the battery voltage will shortly stabilize at its real voltage. At this point, you can get an accurate reading of the battery voltage.

Unfortunately, if the battery is in very bad shape it may immediately switch off the UPS and you may experience immediate shutdown. If the software was monitoring the UPS, it might have recorded one entry with very low voltage before shutdown.

Please consider replacing your batteries if any of the following conditions apply:

• UPS shows low battery level despite you have charged it for sufficient time

• UPS LCD displays weak batteries (depends on model)

• UPS is running for more than 3 years without a battery change

• The backup time has substantially reduced compared to the initial performance

• Regularly performed battery test (scheduled by software) will report issues with the batteries

Naturally the new batteries should have the same technical specification as old ones to ensure full compatibility. The only exception is the most critical parameter – energy capacity given in ampere hour (Ah), this may be the same, bigger or under some conditions even smaller than existing batteries. If you insist to install batteries of smaller capacity, please consult with us.

Attention: Always replace all batteries inside the UPS at the time, never mix old and new ones. Use only one type of batteries, never install mixed types of batteries.

Battery Capacity (Ah) will directly influence the backup time, but it will remain compatibile with the UPS if other parameters are fulfilled. Please pay attention to the parameters:

• Dimensions must be 99 x 65 x 151 +/-2 mm, equipped with T2 terminal – the battery must fit into the same place

• Special UPS batteries for deep-discharge application; never use car batteries

• Nominal voltage: 12VDC; Float charging voltage 13.6-13.8VDC or wider; Cycle use charging voltage 14.5-15.8VDC or wider

• Maximum continuous discharge current: minimum 40A

• Maximum charging current: minimum 2A

• Capacity recommended minimum as the batteries being replaced

• Working temperatures must fit your environment (consider for special desert/arctic applications)

Hint: As it may seem that there are many parameters to check, in fact there is a common industry standard for UPSs and in most cases asking for UPS batteries at your local store will suffice.

Different battery manufacturers provide different ways to determine the battery capacity. There is little standardisation, and parameters may vary between battery manufacturers. For that reason, some battery manufacturers provide battery capacity in different formats, like “300W/5min” or other useful data.

Essentially, a 7Ah battery means it will provide 0.35A (current) for 20h (total 20h x 0.35A = 7Ah). This value is always given in reference to 20h time period, as agreed by the industry. It is false to assume it may provide 35A for 0.2h (12min).

Why is that? Inside the battery, a chemical reaction has to take place. The battery is capable of delivering the shown battery capacity under a 20h span, but under less time, the chemical reaction cannot take place completely (it is not fast enough).

The most generic 7Ah batteries are capable to supply around 12A for 12min, which is a better performance then a 8Ah battery with a normal chemical delivery of 0.4A for 20h.

This batteries are called “high discharge” batteries. Despite having the same nominal 20h battery capacity, they can deliver even 50% more power for shorter periods like 5-10min! Rating by far more critical for UPS application than 20h-rating batteries.

You can buy replacement batteries at your local dealer or at BlueWalker GmbH