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Author Topic: Things to Know before buying an inverter  (Read 353 times)

Offline judejibs (OP)

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Things to Know before buying an inverter
« on: March 30, 2015, 02:13:52 PM »
So it turns out you have been thinking of an alternative to your everyday purchase of Fuel for your generator, also hoping there will be a miracle soon and we have constant light. I too hope so, but in the meantime why don?t you save yourself the risk of storing fuel in gallons and think about a Power Inverter and become your own NEPA. After-all we are in the Jet age.

Are you planning to buy or upgrade your inverter in this season? Then instead of being trapped in the marketing gimmicks, understand some basic facts and do a little bit home work. Here some facts you must know before buying an inverter

Calculate your power requirements

Before going to purchase an inverter- You have to make a rough estimation of your power requirements. remember- Inverter is not a Generator.

Wattage rating of typical home appliances

Appliances Power

Fan (Ceiling) 50-75 Watts

Fan (Table) 25-50 Watts

CFL 18 Watts 18 Watts

Computer (Desktop) 80- 150 Watts

Laptop 20- 75 Watts

LCD TV (32?) 150 Watts

Refrigerator 160 ? 250 Watts

Tube Light (4 Feet) 40 Watts

Starting power and running power

Starting and running power requirement of all electric appliances are different. An 18 Watts CFL takes around 25 Watts power to start and after few seconds it stabilizes to 18 Watts. Some appliances like Refrigerator, Washing Machine etc take almost double power to start as compared to the normal running power. Hence before selecting an inverter you must calculate the starting power requirement also.

Difference between VA and Watts

Often people confuse with the difference between Watts and VA ratings of inverter or other home appliances. Manufacturers use both these terms according to their requirements to confuse and mislead the consumers. Power drawn by the equipment (Power using equipment like Bulb, Fridge, Washing Machines, ACs, Stabilizers etc.) and Power generated by the equipment (Generators, Inverters, UPS etc) can be expressed in Watts or VA (Volt Ampere). In general Power generating or stabilizing equipment manufacturers use the term VA to specify their ratings and power consuming products use Watts to specify their ratings. Here comes the difference. Power in Watts is the real power drawn or supplied by an equipment, this is the real value. VA is the apparent power (more theoretical) which is obtained by multiplying the Voltage and Current drawn/supplied by an equipment. We can equate the VA and Watts ratings:

Power in Watts = Power in VA- Losses


Power in Watts = Power in VA x Efficiency of the equipment

The ratio of Power in Watts to Power in VA is termed as Power factor. Unfortunately manufacturers often don?t specify the power factor or efficiency in their products.

Let?s see an example. You are purchasing an inverter with 650 VA power ratings. This 650 VA indicates, it can supply 650 VA power under ideal situations( means efficiency of the inverter is 100%). If we take 80% as a typical efficiency figure, the said inverter can supply 80% of 650 = 520 Watts only. Now you can understand why inverter manufacturers only publish the VA rating on their products. If an inverter or UPS is coming without mentioning power factor, you must take a safe value of 0.6 (60%) as power factor while connecting appliances.

Digital Inverter

What is digital in inverters? First generation inverters were using power transistors as switching devices and transistorized circuitry for monitoring/controlling applications. That is an old story. Nowadays inverter technology has changed a lot. A complete transition from old square wave technology to Pure Sine wave technology with the help of advanced Digital Signal Processing (DSP) techniques. Micro controllers are extensively utilized for pr?cised monitoring and controlling applications. Switching transistors are replaced with high efficient MOSFETs.


Battery- the vital part of inverter. Performance and life of an inverter greatly depends upon battery. We can see several classifications of inverter batteries. Normally high power Lead Acid batteries are used to power inverters. Lead acid batteries are classified in to different types as per application, design, technology etc.

Battery Capacity

Capacity of a battery is expressed in terms of Ampere Hour (Ah). It indicates the rate of current a battery can supply for a given duration. If the capacity of a battery is 100 Ah, that battery can supply 100 Ampere current for 1 Hour or 1 Ampere Current for 100 Hrs, 2 Amps Current for 50 Hrs .Capacity of inverter batteries are generally 100 Ah, 150 Ah or 180 Ah 200Ah, 260 Ah up to 1660Ah

Why automotive batteries are not suitable for inverters?

Lead acid batteries used for automotive purpose are termed as ?High Cycle? lead acid batteries. These batteries are designed to provide high current for a very short duration (To start the vehicles). Automotive lead acid batteries are not designed to be regularly discharged by more than 25% of their rated capacity. Here the requirement of inverter is totally different. Inverter require ?Deep Cycle? type batteries to provide continuous power which can be discharged at least 50% of their rated capacity. Some good deep cycle batteries can be discharged over 80% of their capacity. Deep Cycle batteries have specially designed thick plates known as AGM to withstand frequent charging and discharging.

If you like a fit and forget inverter system or your situations don?t permit you to do periodic maintenance of batteries then go for a maintenance free battery. Let me quote one example- My friend uses Maintenance free batteries in his home because his old aged mother is living alone and she doesn?t have enough knowledge on battery maintenance. In that situation maintenance free battery the best choice.

Tubular batteries

This is the most popular segment of inverter batteries-Tubular batteries have several advantages compared to flat plate batteries. More complex design increases the manufacture cost but the high electrical efficiency and extra long life make tubular batteries suitable for both domestic and industrial applications. A good maintained tubular battery can run unto 8 years or more. Tubular batteries comparatively require less maintenance. Cost of tubular batteries can go up to double of a normal flat plate battery, however if you have a high efficiency inverter like Xantrex then go for a tubular battery, you will not regret..

To Be Continued...
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