1.
WHAT SIZE INVERTER MUST I USE :
ICM stocks many different sizes, and several brands of
power inverters for solar and commercial use. We also carry
a range of professional telecom inverters.
The inverter size you choose depends on the power in
watts (or current in amps) of the appliance/equipment you
want to run (find the power consumption by referring to the
specification plate on the appliance or tool or you will
find the information in the appliance manual. If this
information is not available, check with the appliance
supplier). You need to know both the continuous rating in
watts or amps; and the peak/surge rating in watts or amps.
Without this information any further calculation is not
possible.
CONTINUOUS vs PEAK/SURGE WATTS
Inverters are rated in continuous power and peak/surge
power. Continuous power is the total WATTS the inverter can
support indefinitely while peak/surge power is the amount of
power that the inverter can provide for a brief period,
usually when the equipment/appliance starts up. Induction
motors driving such devices as air conditioners,
refrigerators, freezers, pumps, etc. may well have a start
up peak/surge of 3 - 7 times the continuous rating.
CONVERTING AMPS TO WATTS
Multiply the equipment/appliance AMPS x 230 (AC voltage)
= WATTS (approximate)
WORKING OUT THE POWER
Multiply the equipment/appliance AMPS x 230 V (AC
voltage) to give the approximate WATTS or AC power.
CALCULATE APPROXIMATE STARTUP LOAD (PEAK/SURGE WATTS)
Multiply the equipment/applicance WATTS x 3 = PEAK/SURGE
WATTS (approximate)
So if you want to run an appliance with a continuous load
of 5 Amps and a peak load of 15 Amps :
Power : V x I = VA i.e. 230VAC x 5A = 1150 Watts continuous
power
Power : V x I = VA i.e. 230VAC x 15A = 3450 Watts peak/surge
(also known as start or inrush current)
You would need an inverter with a continuous rating of
approximately 1500 watts and with a peak/surge rating of
approximately 3500 watts. It is always advisable to build in
a safety factor by overrating the continuous rating by 20 -
25% .
2. WHAT IS THE DIFFERENCE BETWEEN A MODIFIED SINE
WAVE (also known as Square wave) INVERTER AND A PURE SINE
WAVE INVERTER :
Inverters have either modified sine wave
(square wave) or pure sine wave output.
PURE SINEWAVE INVERTER :
This is the best output waveform you can get out of an
inverter and all appliances are able to run off it without
interference or overheating. Some of its advantages are as
follows:
- Output voltage waveform is pure sine wave with very
low harmonic distortion and the same as the ESKOM supply
- Inductive loads like microwave ovens and motors run
correctly, quieter and cooler
- Reduces audible and electrical noise in fans,
fluorescent lights, audio amplifiers, TV, Game consoles,
Fax, and answering machines
- Prevents crashes in computers, unreadable print
outs, and glitches and noise in monitors
- It can be efficiently electronically protected in
overload, overvoltage, under voltage and over
temperature conditions
MODIFIED SINE WAVE INVERTER :
The Modified sine wave inverter has limitations. These
are some of the appliances that may experience problems when
running off Modified Sine wave inverters:
- Laser printers, photocopiers, magneto-optical hard
drives
- Some fluorescent lights with standard ballasts
- Power tools employing "solid state" power or
variable speed control
- Some battery chargers for cordless tools
- Produces sometimes interference in some television
sets
- Digital clocks with radios
- Sewing machines with speed/microprocessor control
- Medical equipment such as oxygen concentrators
- Modified sinewave inverters are usually only
protected by standard fuses which, under normal
circumstances, are not always fast enough, therefore
they are by far more vulnerable to failure.
It is definitely advantageous to use a pure sinewave
inverter as a pure sinewave inverter can basically run any
type of equipment in contrast to a modified sinewave / step
square wave inverter.
3. HOW TO CONNECT AN INVERTER :
The small inverters (150 watts) come with a cigarette
lighter adapter, and may be plugged into your car's lighter
socket. Units from 300W and above, are supplied with DC
connection cables that must be firmly connected directly to
a battery.
Larger inverters (300 watts and over) must be hard-wired
directly to a battery. The cable size depends on the
distance between battery and inverter, and will be specified
in the Owner's Manual.
When connecting the inverter to the battery use the
thickest wire available, in the shortest length practical.
NOTE: Cable size
recommendations may vary among inverter brands and models;
check the Owner's Manual for the model you purchased before
you buy the wire for it.
4. WHAT TYPE OF BATTERY SHOULD I USE :
Small Inverters : Most vehicle and marine
batteries will provide an ample power supply for 30 to 60
minutes even when the engine is off. Actual time may vary
depending on the age and condition of the battery, and the
power demand being placed on it by the equipment being
operated by the inverter. If you use the inverter while the
engine is off, you should start the engine every hour and
let it run for 15 minutes to recharge the battery.
300 Watt and larger Inverters: We recommend you use deep
cycle (marine or solar) batteries which will give you
several hundred complete charge/discharge cycles. If you use
the normal vehicle starting batteries, they will wear out
after about a dozen charge/discharge cycles (vehicle
batteries are not designed to do this type of work!).
When operating the inverter with a deep cycle battery,
start the engine every 30 to 60 minutes and let it run for
15 minutes to recharge the battery.
When the inverter operates appliances with high
continuous load ratings for extended periods, it is not
advisable to power the inverter with the same battery used
to power your car or truck. If the car or truck battery is
utilized for an extended period, it is possible that the
battery voltage may be drained to the point where the
battery has insufficient reserve power to start the vehicle.
In these cases, it's a good idea to have an extra deep cycle
battery for the inverter (installed close to the inverter),
cabled to the starting battery. It is recommended to install
a battery isolator between the batteries with a separate
regulator.
5. HOW LONG CAN I RUN THE APPLIANCES FROM THE INVERTER
:
This depends on the battery size selected and the type of
batteries used.
Deep cycle (marine/solar) batteries generally have the
highest reserve ratings. They are specifically designed to
withstand repeated drains of power and recharging.
Vehicle start batteries should not be discharged below
90% charged state, and marine/solar deep cycle batteries
should not be discharged below 50% charged state. Doing so
will shorten the life of the battery based on most battery
manufacturers’ recommendations.
Note: If you intend to use power tools for commercial
use, or any load of 200W for more than 1 hour regularly
(between battery recharging) we recommend installing an
auxiliary battery to provide power to the inverter. This
battery should be a deep cycle type and sized to meet your
run time expectations with the vehicle engine off. The
auxiliary battery should be connected to the alternator
through an isolator/regulator module to prevent the inverter
from discharging the vehicle start battery when the engine
is off. br>
CAN I CONNECT TWO OR MORE BATTERIES :
It may be advisable to operate the inverter from a bank
of 12, 24 or 48 Volt batteries of the same type in a
"series" and/or "parallel" configuration.
If you parallel two such batteries this will generate
twice the amp/hours of a single battery; three batteries
will generate three times the amp/hours, and so on. This
will lengthen the time before your batteries will need to be
recharged, giving you a longer time that you can run your
appliances.
You can also connect 12 Volt batteries together in
"series" configuration to double the voltage to 24 or 48
volts. Connecting batteries in “series” or “parallel doesn’t
damage the batteries.
