An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically the utility main, fails.

There are three typical types of UPS: OFF-LINE, ON-LINE, and LINE INTERACTIVE. 

An Online UPS takes incoming power, converts it to DC, conditions it, and converts it back to AC. This means the UPS is Online since there is no delay to switch to battery. Use an online UPS for your critical applications, high availability servers, etc. The output of these online UPS systems is a TRUE sine wave and is usually better than power from the electric company.

In this type of UPS, the primary power source is line power from the main utility, and the secondary power source is the battery. The battery charger is using line power to charge the battery, and the battery and inverter are waiting “on standby” until they are needed. When the line power fails, the transfer switch changes to the secondary power source. When line power is restored, the UPS switches back

 Line Interactive UPS under normal conditions smoothes and to some degree regulates the input AC voltage by a filter and a tap-changing transformer. The bi-directional inverter/charger is always connected to the output of the UPS and uses a portion of AC power to keep the battery charged. When the input power fails, the transfer switch disconnects the AC input and the battery/inverter provides output power. Its typical efficiency is 90-96%. This type is currently the most common design in the 500 VA – 5000 VA power range

Every UPS will supply power to a load (such as a computer, telephone switch, or medical equipment) when mains power fails. It may also condition the power and prevent spikes, brownouts, interferences, and other unwanted problems from reaching the supported equipment

Power disturbances and blackouts can be costly.  Preserving Information, the availability of equipment critical to the business, maintaining fully occupied staff, reduction of cost over-runs, performing reliably, and getting results on time are all key elements in any successful operation.  A UPS will provide clean, stable power to critical application equipment throughout utility power disturbances and power failure. 

As long as you want, providing you buy enough batteries and the charging system is up to it. After about four hours it’s usually more cost-effective to buy a generator, with a short run time UPS to bridge the generator start-up gap

Most plug-in UPS are good for at least five years. We’d advise you to change the batteries every three to four years. With larger equipment (and more substantial investment), the lifetime of the equipment increases. We maintain equipment that’s twenty years old and still going strong.

There are three simple methods:
1.    Never overload your UPS.
2.    Never connect any home electronic devices such as a cooling fan to your UPS. This may cause a malfunction of UPS.
3.    Discharge the battery at a consistent interval. The best way to do it is once a month or once two months. The simplest discharge way is to turn on the UPS without connecting the mains

The capacity of the VRLA battery means that when the battery is fully charged and discharge at some condition to the stated end voltage, the capacity is released out, the unit is Ah. For example, when the battery discharges at 1A current for 1 hour, that’s the 1Ah capacity. If the battery discharges at 4A current for 3 hours to the end voltage, the released capacity is 12Ah.

Originally Answered: When removing a battery from a vehicle, which terminal is disconnected first?
Always negative. Simple reason. The entire body of the car along with the engine is connected to the negative terminal of the battery. If you’re disconnecting the positive terminal first, and the spanner touches any part of body or engine, you’ll get a massive spark and potentially damage your battery also. By disconnecting the negative first, you eliminate the risk of *grounding” your battery on the car body or engine.

EPV is the battery end load voltage in the condition of discharge. Many kinds of standards rule EPV definitely in different discharge rates and temperatures. EPV is different according to different discharge rates: it is low when discharge in high current, contrarily, it is high when discharge in low current.

The self-discharge, also known as charge retention capacity, means when it is in an open-circuit state, the maintainability of the battery’s storage electricity under certain environmental conditions. During storage time, the rate of capacity loss is called the self-discharge rate. It is mainly affected by the manufacturing technology, materials, storage conditions, and other factors, which is an important parameter to measure the battery’s performance.