QUESTION - INVERTERS, BATTERYS & UPS

FREQUENTLY ASKED QUESTIONS - Inverters

An inverter takes DC power (battery or solar, for example) and
converts it into AC "household" power for running electronic equipment and appliances.

A UPS typically includes the battery and battery charger in one stand-alone unit. However, there are UPS systems that use external batteries, and Power Stream makes inverters with battery chargers, so the differences blur as features proliferate.

Originally converters were large rotating electromechanical devices. 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 result is AC-IN DC-OUT. If you invert the connections to a converter you put DC-IN and get AC-OUT. Hence an inverter is an inverted converter.

These are old-fashioned inverters, 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. The modified sine wave is designed to minimize the power in the harmonics while still being cheap to make.

Some inexpensive stereos use power supplies that cannot eliminate common-mode noise. These would require a sine wave inverter to operate noise-free.

Definitely not! If you have a generator on board or a grid connection you must install a Master switch. The switch is available with various applications, but its main function is to switch automatically and safely between grid, generator and inverter power.

Yes, you can. All sine wave inverters can easily and safely supply power to a computer. In fact the output voltage from an inverter is often better than that from the electricity grid.

Yes. You can connect any model of microwave to your inverter, but keep in mind that a 800 watt microwave consumes 1200 to 1300 watt from the 230V system, so you must make sure you choose the correct size inverter.

9) Are there any appliances that cannot be run on an inverter?

In general you can connect almost any appliance to an inverter, with a few practical exceptions. While the inverter can easily supply a heavy load like an electric heater, the battery capacity is often too low to maintain the supply for any great length of time. The same applies to air conditioning units. As long as the battery capacity is high enough you can use a large inverter to run a washing machine, a large single cooking element or a small two-ring electric cooker.

10)

If you connect a 850W coffee machine to a sine wave inverter, consumption will be 850W divided by the voltage of the electrical system (12V) = 70 Amperes. Add another 8% (100%-92% =8%) to this total for the inverter consumption. The total power consumption is then 70 Amperes + 6 Amperes = 76 Amperes. Of course a coffee machine is only in use for about 10 minutes so the actual Ampere consumption is relatively low (76 x 10 min = 13Ah).

If you connect a 850W coffee machine to a sine wave inverter, consumption will be 850W
divided by the voltage of the electrical system (12V) = 70 Amperes. Add
another 8% (100%-92% =8%) to this total for the inverter consumption. The total power
consumption is then 70 Amperes + 6 Amperes = 76 Amperes. Of course a coffee machine
is only in use for about 10 minutes so the actual Ampere consumption is relatively low
(76 x 10 min = 13Ah).

11)

Determine Continuous Load and Starting (Peak) Load: You need to determine how
much power your tool or appliance (or combination of them that you would use at the same
time) requires to start up (starting load), and also the continued running requirements
(continuous load).
What is meant by the terms "continuous-2000 watts" and "peak surge-4000 watts" is that
some appliances or tools, such as ones with a motor, require an initial surge of power to
start up ("starting load" or "peak load"). Once started, the tool or appliance requires less
power to continue to operate ("continuous load")

Helpful formulas:
To Convert AMPS to WATTS:
Multiply: AMPS * AC (voltage) * η (efficiency of Inverter) = WATTS
This formula yields a close approximation of the continuous load of the appliance
To calculate approximate Startup Load:
Multiply: WATTS * 2 = Starting Load
This formula yields a close approximation of the starting load of the appliance, though
some may require an even greater starting load.

NOTE: Induction motors such as air conditioners, refrigerators, freezers and pumps may
have a start up surge of 3 to 7 times the continuous rating.

Most often the start up load of the appliance or power tool determines whether an inverter
has the capability to power it.

12)

Advantages of Pure Sine Wave inverters over modified sine wave inverters:

a) Output voltage waveform is pure sine wave with very low harmonic distortion and clean power like utility-supplied electricity.
b) Inductive loads like microwave ovens and motors run faster, quieter and cooler.
c) Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.
d) Prevents crashes in computers, and glitches and noise in monitors.
e) Reliably powers the following devices that will normally not work with modified sine wave inverters:
     -> Laser printers, photocopiers, magneto-optical hard drives
     -> Certain laptop computers (you should check with your manufacturer)
     -> Some new furnaces and pellet stoves with microprocessor control
     -> Sewing machines with speed/microprocessor control
     -> Medical equipment such as oxygen concentrators
     -> The difference between them is the Pure Sine Wave inverter produces a better and cleaner current. They are also considerably more expensive. You might find it practical to get a small Pure Sine Wave inverter for any "special need" you may have, and also a larger Modified Sine Wave inverter for the rest of your applications.

13)

Keep the cables between your inverter and batteries as short as possible. This will help your batteries perform their best and keep the inverter's signal clean. The cables that come with the inverter are "rated" or good for up to six ft. If you plan on going over six ft., drop down to a larger gauge cable. Please call us if you are still unsure. This is pretty important stuff that should NOT be overlooked. If the cables between your battery and inverter get hot while under heavy load, then you should use heavier cables.

14)

The low voltage alarm will sound when the DC source falls below a certain level and the automatic shutdown will power off the inverter. This is done to save your batteries; you can restart your inverter once grid power is available.

15)

No. Treat your inverter like you would your TV. You wouldn't put your TV outside in the rain, please don t leave your inverter there either. Be aware of lighting storms. If struck, your inverter would go into a permanent overload state and may even smoke it. If using in a marine environment, try to keep it tucked away underneath, in a dryer area.

FREQUENTLY ASKED QUESTIONS - UPS

The equation is KW= KVA *PF. In general KW is active or useful power and KVA is the
vector sum of active power and reactive power. The equation is kW= KVA *PF.

- Power factor is a function of phase displacement angle between voltage and current and
- distortion factor. It is calculated as a ratio of real power to apparent Power drawn by load.
- PF is low at lower loads and goes on improving at higher loads. PF is also lower at higher
- input voltage and goes on improving as voltage reduces. Input Power Factor is independent
- of type of load for double conversion technology.
  For nonlinear loads the power factor is low due to the presence of high percentage of
- harmonics present in the load current.

Estimate steady state (normal running) KVA of the total load. Determine inrush KVA of the
largest load in the total load distribution. The rated KVA capacity of the UPS should be 85%
of the sum of above two [Steady state KVA + In rush KVA].
This is under the assumption that all loads are not switched on at the same instant and largest
load is started while all remaining loads are running

4) What is the % total harmonic distortion (%THD) of the UPS output voltage and how it is
measured?

Total Harmonic Distortion is measured using Distortion meter. For linear load it is less than 1%

typical and less than 2% maximum. For nonlinear load with crest factor 3:1 it is less than 5%.

Yes, double wound isolation transformer of full load UPS rating is used at inverter output, which
ensures complete isolation from input.

6) Can the UPS output neutral be earthed?

Yes, provided bypass isolation transformer is used or the operation of static switch is permanently

disabled.

Fan failure is not directly indicated because on failure of fan heat sink temperature of UPS will
increase and this rise is depends upon percentage of load on UPS. Fan failure indirectly indicated
as 'Over temperature'.

FREQUENTLY ASKED QUESTIONS - Batteries

Proper battery selection may require the assistance of a knowledgeable battery sales/service
technician. Please contact your local Luminous Battery distributor or SMS 'Luminous' to
6161 and our technical experts will contact you.

A deep cycle battery has the ability to be deeply discharged and charged many times during its
service life. It is designed specifically for powering electrical equipment for long periods of time.
An automotive or starting battery is designed for brief bursts of high current and cannot withstand
more than a few deep discharges before failure. A tubular positive plate battery is an ultra deep
cycle battery. It provides more than double the life of a typical thick flat deep cycle battery.

Deep cycle batteries can be used for engine starting but starting batteries should not be used for
deep cycle applications. A deep cycle battery may have less cranking amps per Kg than a
starting battery and thus may have to be oversized by about 10% to 20% but in most cases
a deep cycle battery is still more than adequate for the purpose of starting an engine.

Deep cycle batteries can be used for engine starting but starting batteries should not be
used for deep cycle applications. A deep cycle battery may have less cranking amps
per Kg than a starting battery and thus may have to be oversized by about 10% to
20% but in most cases a deep cycle battery is still more than adequate for the purpose
of starting an engine.

4) What are the advantages and disadvantages of , AGM, and flooded lead acid deep cycle?

Generally AGM batteries have about 20% less capacity, cost about two times more, and
have a shorter cycle life than comparable flooded lead acid batteries. However, AGM
batteries do not need watering, are safer (no acid spilling out), can be placed in a variety
of positions, have a slower self-discharge characteristic, and are more efficient in charging
and discharging than flooded batteries (see table below). Tubular and flat plate deep cycle
batteries are more suitable for applications whereas AGM batteries are more for light

cycling applications where power cut duration are low.

	Flodded	AGM

Charge/Discharge Efficiency	93%	99%

Self discharge rate (per month)	7%	1-3%

Finish Voltage	15.3-16.0V	14.1-14.4V

Float charge	13.2-13.7V	13.4-13.8V

Higher-voltage systems tend to be more efficient and put a lower load on the batteries. Factors
other than the battery enter into the system's overall efficiency.

At higher temperatures (above 27^oC) battery capacity generally increases, usually at the cost
of battery life. Higher temperatures also increase the self-discharge characteristic. Colder
temperatures (below 27^oC) will lower battery capacity and prolong battery life. Cooler
temperatures will slow self-discharge. Therefore, operating batteries at temperatures at or
slightly below 27^oC will optimize both performance and life.

7) How do I determine my battery capacity when it is colder / hotter?

Battery capacity is basically a linear relationship. A good rule of thumb is that for every 1^oC

above 27^oC, capacity is increased by 0.5% and for every 1^oC below 27^oC; capacity is reduced

by 0.5% rated battery.

Temperature will affect specific gravity readings. As temperature increases, the electrolyte
solution expands and as temperature decreases the electrolyte solution contracts. As a result,
it is a good practice to temperature correct specific gravity readings. Here is the relationship
Luminous recommends using: For every ten degrees above 27^oC add 7 points to the hydrometer
reading.

Temperature will affect voltage readings. As temperature increases, voltage decreases. Conversely,
as temperature decreases, voltage increases. Here are the relationship Luminous recommends using:
For every 5 degrees C below 27^oC, add .028 volt per cell to the charger voltage setting.

10)

When charging lead acid batteries, the temperature should not exceed 52^oC intermittently or 45^oC
. At this point the battery should be taken off charge and allowed to cool before resuming the
charge process.

11)

Water is lost during charging. Therefore, the best time to water your batteries is always at the
end of the charge cycle. However, if the electrolyte level is extremely low or the plates are
exposed to air, add some water to cover the plates before starting the charge cycle. After
addition of water, continue change at a low rate for some more time to allow electrolyte mixing.

12)

How often you discharge and recharge your batteries will determine the frequency of watering.
Also using batteries in a hot climate may require more frequent watering. It is best to check
your new batteries regularly as this will give you a good feel for how often your application
will require battery watering.
WARNING: A brand new battery may have a low electrolyte level. Charge the battery first
and then add water if needed. Adding water to a battery before charging may result in overflow
of the electrolyte.

13)

Liquid levels should be 1/8 inch below the bottom of the vent well (the plastic tube that extends
into the battery). The electrolyte level should not drop below the top edge of the plates.

14)

Under normal operating conditions, you never need to add acid. Only distilled, deionized or
approved water should be added to achieve the recommended levels mentioned above.
When a battery is shipped in a dry state or accidental spillage occurs, electrolyte should be
added to the battery. Once filled, a battery should only need periodic water addition.
*Do not over tighten terminals. Doing so can result in post breakage, post meltdown,
and fire.

15)

The only way that a battery can freeze is if it is left in a state of partial or complete discharged.
As the state of charge in a battery decreases, the electrolyte becomes more like water and the
freezing temperature increases. The freezing temperature of the electrolyte in a fully charged
battery is -68.88^oF. At a 40% state of charge, electrolyte will freeze if the temperature reaches
approximately -8.88^oF.

16)

A hydrometer reading of 1.250 or greater indicates full charge for luminous batteries. This value
is based upon a specified temperature of 77 to 80^oF. For temperature correction values,
see the "Temperature" section of this FAQ.

17)

Undercharging: Generally caused by not allowing the charger to restore the battery to full
state of charge after use. Continually operating the battery in a partial state of charge, or storing
the battery in discharged state results in the formation of lead sulfate compounds on the plates.
This condition is known as sulfation. Both of these conditions reduce the battery's performance
and may cause premature battery failure. Undercharging will also cause stratification.
Overcharging: Continuous charging causes accelerated corrosion of the positive plates, excessive
water consumption, and in some cases, damaging temperatures within a lead acid battery.
Deep cycle batteries should be charged after each discharge of more than 50% of the batteries
rated capacity, and/or after prolonged storage of 45 days or more.
Under watering: In deep cycle, lead acid batteries water is lost during the charging process.
If the electrolyte level drops below the tops of the plates, irreparable damage may occur.
Water levels should be checked and maintained routinely.
Over-watering: Excessive watering of a battery results in additional dilution of the electrolyte,
resulting in reduced battery performance. Additionally, watering the battery before charging
may result in electrolyte overflow and unnecessary additional maintenance.

18)

You will reduce the frequency of watering, but will cause a condition known as stratification where
the specific gravity of the electrolyte is light at the top of the battery and heavy at the bottom.
This condition results in poor performance and reduced battery life. The higher concentration of
electrolyte at the bottom causes heavy sulfation on the bottom part of the plates. The lower
concentration of the electrolyte at the top causes hydration at the top part of the plates.

19)

To determine if the battery system is experiencing a problem, fully charge the batteries then shut
off the charger and remove all electrical loads. Allow each battery in the system to stand on
open-circuit for about one hour. Measure the voltage of each battery. If the battery voltage
spread exceeds .30 volts for a 12 volt battery, a problem is indicated. Battery voltage alone
does not confirm a problem. When the voltage spread indicates a problem, confirmation is
accomplished by taking electrolyte specific gravity readings using a hydrometer. If the specific
gravity readings show a spread greater than .030 (30 points), give the batteries equalization
charge i.e slow constant current charge @ 3% of the battery capacity in amperes.