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FAQ

FREQUENTLY ANSWERED QUESTIONS

Q 1: What is the inverter ?

Inverter Tutorial and Frequently Asked Questions:

Q: What is an inverter? 

A: An inverter takes DC power (from a battery or solar panel, for example) and converts it into alternating current (AC) "household" power for running electronic equipment and appliances. 

Q: Why are they called inverters?
A: Originally converters were large rotating electromechanical devices used to convert AC to DC. It is what you have to do if you don't have semiconductor or vacuum tube rectifiers. Essentially they combined a synchronous ac motor with a commutator so that the commutator reversed its connections to the ac line exactly twice per cycle. The results is ac-in dc-out (with a lot of switching noise thrown in). If you invert the connections to a converter you put dc in and get ac out. Hence an inverter is an inverted converter. For more information about such converters see http://www.nycsubway.org/tech/power/rotary.html(thanks to Karl W.Berger, PE for this answer).

Q: How is an inverter different than a UPS? 

A: A UPS typically includes the inverter, battery and battery charger in one stand-alone unit. However, there are UPSs that use external batteries, and PowerStream has made inverters with battery chargers, so the differences blur as features proliferate.

UPSs also can have communication with the equipment that it is powering, which lets the equipment know that it is operating on standby, giving it shutdown warning, or communicating with the human in the loop. Inverters typically don't have this communication.


Q: What if I want a DC output to run such things as a laptop from a car cigarette lighter, or telephone equipment at -48 volts?
A: Then you want a DC/DC converter. PowerStream has many DC/DC converters just for those purposes. http://www.powerstream.com/dcdc.htm 

Q: What is the difference between sine wave and modified sine wave?
A: Alternating current (AC) has a continuously varying voltage that swings from positive to negative. This has great advantages in power transmission over long distances. Power from your power company is carefully regulated to be a perfect sine wave, because that is what naturally comes out of a generator, and also because sine waves radiate the least amount of radio power during long distance transmission. 

On the other hand, a sine wave is expensive to make in an inverter, and many sine wave techniques use heavy, inefficient transformers. The most inexpensive way to make AC is to switch the DC on and off--a square wave. A modified sine wave is scientifically designed to simulate a sine wave in the most important respects so that it will work for most appliances. It consists of a flat plateau of positive voltage, dropping abruptly to zero for a while, then dropping again to a flat plateau of negative voltage, back to zero for a while, then returning to the positive voltage. This pause at zero volts puts more power into the 60HZ fundamental than a simple square wave does, so it is called "modified sine wave" instead of "square wave." Because the MOSFETs only have to turn completely on and completely off the dissipate he least amount of heat for the power generated, and so smaller semiconductors and heat sinks are needed than if you were trying to generate a real sine wave.


Q: Can I use a modified sine wave inverter for my medical equipment?
A: For Medical equipment, oxygen generators, etc. talk to the manufacturer of the equipment. PowerStream inverters are never tested or rated with medical equipment, and we don't guarantee that they will work to save your life. For such applications please find inverters that are rated and tested for such applications.

Q: What about square wave inverters? 
A: These old-fashioned inverters are the cheapest to make, but the hardest to use. They just flip the voltage from plus to minus creating a square waveform. They are not very efficient because the square wave has a lot of power in higher harmonics that cannot be used by many appliances. Synchronous motors, for example, use the 60Hz component and turn the rest of the frequencies into heat. The modified sine wave is designed to minimize the power in the harmonics while still being cheap to make.

Q: How do I know if I need a sine wave, or if I can live with a modified sine wave?
A: The following gadgets work well with a modified sine wave: electric blankets, computers, motor-driven appliances, toasters, coffee makers, most stereos, ink jet printers, refrigerators, TVs, VCRs, many microwave ovens, etc.

Appliances that are known to have problems with the modified sine wave are some digital clocks, some battery chargers, most light dimmers, some battery operated gadgets that recharge in an AC receptacle, some chargers for hand tools (Makita is known to have this problem in the past). In the case of hand tools, the problem chargers usually have a warning label stating that dangerous voltages are present at the battery terminals when charging. We would like to add to this FAQ any appliances that you have had trouble with, or had success with, using modified sine wave inverters.

Q: Why do I hear buzzing on my stereo when using a modified sine wave inverter?
A: Some inexpensive stereos use power supplies that cannot eliminate common-mode noise. These would require a sine wave inverter to operate noise-free. What you hear is some of the higher harmonics of the modified sine wave.

Q: Why don't I measure rated voltages when using a multimeter on my modified sine wave inverter?
A. The rated voltage is an RMS (root mean square--they square the value to make sure it is always positive, then average it, then take the square root of the average to make up for having squared it in the first place) measurement. Most multimeters are designed to give correct RMS readings when applied to sine waves, but not when they are applied to other waveforms. They will read from 2% to 20% low in voltage. Look for a voltmeter that brags about "True RMS" readings, and that will read correctly no matter what the wave shape is. 

Q: How should I select the right size inverter?
A: First add up the power ratings of all the appliances, then buy the next larger inverter! At least that is the simple answer. Note, however, that some appliances, such as table saws, refrigerators, and microwaves have a surge requirement. PowerStream inverters are designed to supply such surges, but since every appliance has its own requirements sometimes you will need to get a bigger inverter than you would otherwise think. Note that the inverter isn't the only consideration when you are pondering the mysteries of start-up surges. The battery must also be able to supply the surge power, and the cables must be able to supply the increased current without dropping the voltage too much.

Q: How is a microwave rated for wattage?
A: When you buy a microwave oven you want to know how intense the microwave field is, not how much the oven draws from the wall. So a microwave oven that boasts 600 watts on the box, will have an input requirement of 1200 watts on the boilerplate in the back. Don't be fooled!

Q: Are stereo amplifiers rated the same way?
A: Stereo manufacturers are bigger liars than politicians. Some times they use peak output power (milliseconds), sometimes they use power drawn from the wall, but often they just look at the competition's carton front and add 10%. However the truth is available: look at the boilerplate sticker, which has been evaluated by UL. This will give the maximum possible power drawn, so it tends to be higher than you will actually draw.

Q: Why do I need such humongous cables to the battery when a small cord takes the AC output fine?
A: Power is volts times amps (Watts = V x A). So if you have a lot of voltage you don't need many amps to get a watt. Roughly you need 12 times as much current from the 12 volt battery as you need from the 110 volt AC outlet. Current is what causes cables to heat up, not voltage. That is why they use thousands of volts in long distance power transmission grids. The thing to do when you have lots of current is to lower the resistance of the cable. The larger the wire the lower the resistance. Think of the cable as a water pipe. A big pipe (wire) can carry more water (current or amperage) with less pressure (voltage), and will present less pressure (voltage) drop from one end of the pipe to the other.
Another consideration is how far the cable has to run from the battery to the inverter. Long cable runs are expensive, either in copper or efficiency, or both. 

Q: Why would you use a 24 volt inverter instead of a 12 volt inverter?
A. At a given power rating a 24 volt inverter will need half the current as a 12 volt inverter. This makes the entire system more efficient, and since high current transistors are expensive, the inverter will be cheaper.

Q: Should I use aluminum wire, or must I use copper?
A: Aluminum is cheaper and lighter, but it also has higher resistance for a given gauge, and is more difficult to connect to. If you are an expert in such things, or know one, and need the advantages that aluminum gives, go ahead. If not, why not use the best conductor, copper? (Silver is slightly better, but it is cheaper to use a larger diameter copper). To compare the two look at our web page http://www.powerstream.com/Wire_Size.htm .

Make sure to use good insulation, 90°C rated or better. Also, running two sets of parallel wires instead of one large one can cut down on the wire heating due to more surface area.

Make sure to follow all applicable electrical codes. Inverters must be grounded properly, and treated with respect, since they put out potentially lethal voltage. A lot of smart people have worked for 100 years to develop rules which will keep you out of trouble if followed. These rules are called the national electrical code, and your friend the electrician has it memorized (or knows where to look it up).

Q: Should I use a laser printer with an inverter?
A: Only if you must. Laser printers use up a surprising amount of power (due to the heated fusing rollers), and will discharge your battery faster than you expect, even on standby. If you do, make sure the inverter is rated for the power of the printer plus computer plus monitor. It doesn't do any good to have your computer brown out as soon as the the printer starts to print. Ink jet printers, on the other hand, use a surprisingly low amount of power.

Q 2: What are the types of battery?

Comparing the Differences between Deep-cycle Flooded and Deep-cycle Valve-Regulated Lead-acid Batteries for Renewable Energy Applications

Battery-based renewable energy systems vary greatly in size and design based on the purpose and location of the installation. In order to choose the right battery for your system it is important to understand the main differences between deep-cycle flooded, AGM and gel batteries. In this technical bulletin we will discuss the essential differences and benefits of these battery technologies with an emphasis on using deep-cycle batteries in renewable energy storage applications. We will describe how these technologies offered by Trojan differ, their operating principles, features and benefits, and factors that should be taken into account when selecting a battery for a renewable energy storage system.

Deep-cycle lead-acid batteries generally fall into two distinct categories; flooded (FLA) and valve-regulated lead-acid (VRLA), with the VRLA type further subdivided into two types, Absorbed Glass Mat (AGM) and Gel. These differences have evolved because no single design is suitable for all applications. One of the most frequently asked questions is how they differ and what their characteristics are.

Unlike many other battery applications, battery-based renewable energy applications are unique because the batteries in these systems can be discharged and charged in an unpredictable manner due to variations in sunshine, wind and hydro power. They are also subjected to seasonal variations that can result in the batteries having to operate in a partial state of charge for considerable lengths of time. These factors can cause the batteries to result in frequent deep discharges and lack of charge. Consequently, the most important requirement for batteries used in renewable energy systems is long cycle life. Deep-cycle lead-acid batteries are the best choice for renewable energy applications but it should be recognized that there are different types having strengths and weaknesses which influence their suitability and life.

Deep-Cycle Flooded Lead-Acid Batteries (FLA)
Deep-cycle flooded lead-acid batteries are the most popular type in use today for renewable energy systems. Although flooded batteries are available in flat and tubular plate versions this technical brief will concentrate on the flat plate type since this is the most widely used. The term "flooded" is used because this type of battery contains an excess of electrolyte fluid so that the plates are completely submerged. The electrolyte level should be above the tops of plates which serves as a reservoir to make sure that water loss during charging does not lower the level below the plate tops and cause damage.

Here are some of the advantages of using deep-cycle flooded batteries:
• Lower cost than deep-cycle VRLA batteries.
• Longer deep cycle life than deep-cycle VRLA batteries.
• Can be maintained simply by addition of distilled water.
• High discharge rate capability.
• Perform better in hot climates. (>90 degrees F)
• More available worldwide.
• Perform better then deep-cycle VRLA batteries when regularly in a partial state of charge.
• Long, proven history of use.

Some of the drawbacks of using deep-cycle flooded batteries are:
• Periodic maintenance by adding distilled water is required.
• Can only be used in an upright position.
• Produce gas (oxygen and hydrogen) when charged.
• May emit acid spray if overcharged abusively.
• Require ventilation.
• Higher self-discharge rate than deep-cycle VRLA batteries.
• Cannot be shipped by air.
• Cannot be used in the immediate vicinity of electrical equipment or anything highly flammable.

In summary, deep-cycle flooded lead-acid batteries are very versatile and should be the first choice for renewable energy systems where maintenance can be carried out and ventilation is available.

Deep-Cycle Valve-Regulated Lead-Acid Batteries (VRLA)

Deep-cycle VRLA batteries were developed in the late 1960s to eliminate the need for water addition and to provide batteries that could be used in any position. They are designed so that oxygen evolved from the positive plates during charging can migrate to the negative plate where it is reduced to water. This process significantly reduces water loss. In actual practice this is not always the case because the oxygen reduction reaction is not 100% efficient and the surplus oxygen must be vented together with an equivalent amount of hydrogen. For this reason, VRLA batteries are fitted with a pressure vent that allows surplus gas to be vented when the internal gas pressure builds up. This is why they are called valve-regulated, not sealed batteries. Although gas evolution is considerably reduced it is not eliminated entirely and VRLA batteries can still lose water and become dry.

For this process to operate oxygen must be able to migrate from the positive to the negative plates. This can be accomplished in two ways which has led to the development of the two classes of VRLA batteries; AGM and Gel. They get these names because of the mechanisms used to allow oxygen migration.

Absorbed Glass Mat (AGM) Batteries
Deep-cycle AGM batteries incorporate a porous glass mat separator that has the ability to absorb a large amount of electrolyte while still allowing some of the pores to be unfilled. These empty pores act as channels which allow oxygen to move from the positive to the negative plates. This absorptive glass mat is a critical component of the battery since it must be capable of high compression so that good contact can be maintained between the separator and the plates. It must also have high wettability and porosity.

Here are some of the advantages of using deep-cycle AGM batteries:
• Less expensive than deep-cycle Gel batteries.
• Wider temperature range than deep-cycle Gel or FLA batteries.
• Slowest self-discharge rate of FLA, AGM and Gel batteries.
• Best shock/vibration resistance of FLA, AGM and Gel batteries.
• Best for high power applications of FLA, AGM and Gel batteries.
Here are some of the disadvantage of using deep-cycle AGM batteries:
• Don't perform as well as deep-cycle FLA or Gel batteries for systems that require regular deep discharge. (i.e. 80% DOD)
• Do not perform as well as deep-cycle Gel batteries in low power applications.
Gel Batteries
Deep-cycle Gel batteries also work on the same principle of oxygen recombination but use a different method to achieve it. They use a composite separator composed of a glass mat bonded to a porous polyethylene or polyvinylchloride sheet. The batteries are filled with a thixotropic gel of silica mixed with sulfuric acid. When this is added to the battery it fills all of the available space and then sets to form a solid matrix. Because all the pores in the separator are filled there are no oxygen channels and in the early stages of its life the battery behaves in the same way as a flooded type with gas generation and water loss. This causes the gel to dry out, shrink and develop cracks which eventually form the channels for oxygen to migrate to the negative plate and be recombined.

Here are some of the advantages of using deep-cycle Gel batteries:
• Perform better than deep-cycle AGM batteries for systems that require regular deep discharge. (i.e. 80% DOD)
• Perform better than deep-cycle AGM batteries for low power applications.
Here are some disadvantages of using deep-cycle Gel batteries:
• More expensive than deep-cycle FLA or AGM batteries.
• Do not perform as well as deep-cycle FLA or AGM batteries in cold temperatures. (<40 degrees F)
• Do not perform as well as deep-cycle FLA or AGM batteries when they regularly reach a shallow depth of discharge. (i.e. 20% DOD)
• Higher self-discharge rate than deep-cycle AGM batteries.

Battery Considerations for Renewable Energy Applications
In summary, the most important difference between FLA and VRLA batteries is in the oxygen recombination mechanism which eliminates the need to add water to VRLA batteries. While this makes VRLA batteries maintenance-free, it also prevents the addition of water so they are maintenance-proof as well. The elimination of water addition is a valuable feature where the battery installations are in remote areas or where access to the batteries is difficult. However, a penalty is paid for the maintenance-free feature. Their cost of VRLA batteries is higher than flooded batteries and their life is shorter. The shorter life results primarily from their higher operating temperature. The oxygen recombination process produces heat which cannot be shed from the batteries because of the elimination of gas venting. On the other hand the gases emitted from a flooded battery provide considerable cooling. This high operating temperature can shorten the life of the battery by increasing the rate of positive grid corrosion and drying out.

VRLA batteries are preferred in installations where access is difficult or space is limited. Their ability to be operated in any position allows them to be used in spaces where flooded batteries cannot be used, but it is best to use VRLA batteries in an upright position except for large stationary cells designed to be operated in a horizontal manner.There are also important differences between AGM and Gel VRLA batteries. Gel batteries are generally superior to AGM in recovery from deep discharge because they contain more electrolyte and are less susceptible to stratification than either flooded or AGM batteries. Gel electrolyte has a higher resistivity than fluid electrolyte therefore Gel batteries have lower high rate charge and discharge capability than AGM and flooded types.

The advantages of flooded batteries are their well-proven reliability, their long deep discharge cycle life, and their lower cost. They can be made from thick antimony alloy grids which are more suitable for long cycle life than the calcium alloy grids typically used in VRLA batteries. They contain more electrolyte than VRLA batteries which provides good deep discharge recovery and which also acts as a heat sink to keep them cool. Another advantage is that they can be maintained by addition of water. In installations which use a large number of batteries automatic watering systems can be used that increase reliability and reduce labor cost.

Flooded batteries have been used in deep cycle applications for many years and they have been optimized for this type of service. On the other hand VRLA batteries were developed for standby power applications where there is very little cycling, therefore many are not optimized for repeated deep discharging. It is important, therefore, to make sure that a true deep discharge VRLA battery is chosen not a relabeled UPS or standby telecommunications battery. To protect against this the VRLA battery should only be purchased from a

reputable manufacturer that specializes in deep cycle technology and who is willing to provide certified life cycle data. Another consideration when choosing between gel and AGM batteries is the effect of temperature on performance. The capacity of gel batteries is reduced more than either flooded or AGM batteries at low temperature.

In renewable energy installations where maintenance is virtually impossible or where very large numbers of batteries are used resulting in costly maintenance, a VRLA battery is a suitable choice. If the duty cycle involves deep discharge cycling a Gel type may be preferred over an AGM type, however many renewable energy systems are sized to 20% to 50% depth of discharge so an AGM battery would suffice. Where the batteries are accessible for maintenance and maintenance costs are reasonable, flooded batteries will have several advantages over their VRLA counterparts.

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Trojan Battery Company: Founded in 1925, Trojan Battery Company is one the world's leading manufacturing deep-cycle batteries and four ISO 2000:2001quality management certified plants within North America, Trojan Battery Company supports its renewable energy clients through a worldwide network of master distributors in over 50 countries. With the largest R & D facility in the USA dedicated to performance testing of deep-cycle batteries, Trojan battery continually monitors product performance under true life cycle conditions. This dedication to continual product improvement allows us to set the standard for quality and longevity in deep-cycle batteries used in off-grid renewable energy systems.

Q 3: What is the solar energy systems?

How do solar systems produce energy?

Solar power is arguably the cleanest, most reliable form of renewable energy available, and it can be used in several forms to help power your home or business. Solar-poweredphotovoltaic (PV) panels convert the sun's rays into electricity by exciting electrons in silicon cells using the photons of light from the sun. This electricity can then be used to supplyrenewable energy to your home or business.

To understand this process further, let’s look at the solar energy components that make up a complete solar power system.

The roof system

In most solar systems, solar panels are placed on the roof. An ideal site will have no shade on the panels, especially during the prime sunlight hours of 9 a.m. to 3 p.m.; a south-facing installation will usually provide the optimum potential for your system, but other orientations may provide sufficient production. Trees or other factors that cause shading during the day will cause significant decreases to power production. The importance of shading and efficiency cannot be overstated. In a solar panel, if even just one of its 36 cells is shaded, power production will be reduced by more than half. Experienced installation contractors such as NW Wind & Solar use a device called a Solar Pathfinder to carefully identify potential areas of shading prior to installation.

Not every roof has the correct orientation or angle of inclination to take advantage of the sun's energy. Some systems are designed with pivoting panels that track the sun in its journey across the sky. Non-tracking PV systems should be inclined at an angle equal to the site’s latitude to absorb the maximum amount of energy year-round. Alternate orientations and/or inclinations may be used to optimize energy production for particular times of day or for specific seasons of the year.

Solar panels

Solar panels, also known as modules, contain photovoltaic cells made from silicon that transform incoming sunlight into electricity rather than heat. (”Photovoltaic” means electricity from light — photo = light, voltaic = electricity.)

Solar photovoltaic cells consist of a positive and a negative film of silicon placed under a thin slice of glass. As the photons of the sunlight beat down upon these cells, they knock the electrons off the silicon. The negatively-charged free electrons are preferentially attracted to one side of the silicon cell, which creates an electric voltage that can be collected and channeled. This current is gathered by wiring the individual solar panels together in series to form a solar photovoltaic array. Depending on the size of the installation, multiple strings of solar photovoltaic array cables terminate in one electrical box, called a fused array combiner. Contained within the combiner box are fuses designed to protect the individual module cables, as well as the connections that deliver power to the inverter. The electricity produced at this stage is DC (direct current) and must be converted to AC (alternating current) suitable for use in your home or business.

Inverter

The inverter is typically located in an accessible location, as close as practical to the modules. In a residential application, the inverter is often mounted to the exterior sidewall of the home near the electrical main or sub panels. Since inverters make a slight noise, this should be taken into consideration when selecting the location.

The inverter turns the DC electricity generated by the solar panels into 120-volt AC that can be put to immediate use by connecting the inverter directly to a dedicated circuit breaker in the electrical panel.

The inverter, electricity production meter, and electricity net meter are connected so that power produced by your solar electric system will first be consumed by the electrical loads currently in operation. The balance of power produced by your solar electric system passes through your electrical panel and out onto the electric grid. Whenever you are producing more electricity from your solar electric system than you are immediately consuming, your electric utility meter will turn backwards!

Net meter

In a solar electric system that is also tied to the utility grid, the DC power from the solar array is converted into 120/240 volt AC power and fed directly into the utility power distribution system of the building. The power is “net metered,” which means it reduces demand for power from the utility when the solar array is generating electricity – thus lowering the utility bill. These grid-tied systems automatically shut off if utility power goes offline, protecting workers from power being back fed into the grid during an outage. These types of solar-powered electric systems are known as “on grid” or “battery-less” and make up approximately 98% of the solar power systems being installed today.

Other benefits of solar

By lowering a building’s utility bills, these systems not only pay for themselves over time, they help reduce air pollution caused by utility companies. For example, solar power systems help increase something called “peak load generating capacity,” thereby saving the utility from turning on expensive and polluting supplemental systems during periods of peak demand. The more local-generating solar electric power systems that are installed in a given utility's service area, the less capacity the utility needs to build, thus saving everyone from funding costly additional power generating sources. Contributing clean, green power from your own solar electric system helps create jobs and is a great way to mitigate the pollution and other problems produced by electricity derived from fossil fuel. Solar-powered electrical generating systems help you reduce your impact on the environment and save money at the same time!

Q 4: What are the terms of payment and shipping?

Must pay the value of the products and the cost of shipping in full before shipping.

Shipping cost commensurate with the distance from the company's headquarters.

Can deliver the product at the company without the cost of shipping.

Q 5: What are the different payment methods?

Cash

Electronic Payment through Paypal

Bank transfer to our account.

Q6: What are the conditions of Returns & Refunds ?

Returns  within 15 days.

Implementation Terms of Use

Not to misuse

Q7: How can I get your products?

By visiting the company's headquarters and get the product.

Using communication and agreement on the way the payment and ship the product.

Using e-procurement and payment by Paypal.