Captain Tropic's
Power Inverts
As I've pointed out before, electrical power interruptions are common after a hurricane or severe storm. Everyone knows a power outage means no lights, television or refrigerator. So with this in mind I've been searching for an alternate source of electricity to replace this lost power. There are quite a few ways to accomplish this, especially if money is no object. Because I'm not made of money, my main goal was to keep the cost down. Another objective was to keep it simple, because not everyone is an electrical engineer. Finally, reliability was an absolute must, I don't know about you but I have a lot of money staying cool in my refrigerator.
This might be a good place to explain a little about the electrical power we all use every day and take for granted. Direct current (DC) is current that flows in one direction, for example from a car battery. Alternating current (AC) is current that flows alternately in either direction, for example from a household outlet. The frequency at which this change in direction occurs is measured in hertz. An electric current's overall power depends on the amount of current flowing (measured in amperes) and the electric potential driving it (measured in volts). Electric power is measured in watts. One watt is equal to one ampere moving at one volt. Multiplying amperes by volts produces the number of watts used. An appliance that uses 10 amperes and runs on 115 volts consumes 1150-watts of power. Many household appliances run on 115 volts AC, but some require 220 volts AC. In technical terms the electrical power that is available at the standard household outlet is 10 to 15 amperes and 110 volts alternating current at 60 hertz. The electrical power that is available at say your electric cloths dryer outlet is something like 50 amperes and 220 volts alternating current at 60 hertz. So if your dryer uses 50 amps x 220 VAC = 11000-watts, that's a lot of power. Your air conditioning system uses even more power than that, and this is why the electric bill is so high in the summer in Florida.
In my quest to find a good solution to the problem of electrical power outages, I looked at a number of ways to create AC power. One good way I found was gasoline-powered generators. The price on these is still a little too high and there are some other problems associated with them. Such as maintenance and up keep, as well as some very serious safety concerns. Not only that but they do require gasoline and oil, which they tend to use at a high rate. During the time period following a hurricane gasoline and oil would be in short supply.
I did find what I think would be a good solution and that solution is what is known as a power inverter. I bought one and have been using it for quite a while now. It was pretty easy to hook up and it's very simple to use. The price was very reasonable and I special ordered it through Home Depot. I shopped all over the place and they had the best price in town. There are quite a few manufactures that make inverters and there are several whose names you might recognize, but a company called Vector Manufacturing Ltd. located in Fort Lauderdale Florida made the one I bought. I'll give you more information on them at the end of this article.
What follows is my rendering of the owner's manual that came with the unit. I'm going to give you a good look at the manual so you can decide rather or not this idea is for you. I'm not going to cover how to hook one of these up, use the manual that comes with your unit to figure that out. The name of the unit I purchased is the MAXX 1500. The MAXX 1500 is a state-of-the art, highly efficient DC to AC power inverter that changes 12 volts DC from a battery to 115 volts AC. With proper installation, it can continuously deliver up to 1500-watts AC and up to 3000 watts during appliance motor start-up conditions.
Figure 6 - Battery Operating Time
For example, as shown in FIGURE 6, using a 400-amp hour battery (batteries) if the average power usage will be 1500 watts the operating time will be about 150 minutes. A larger capacity battery will deliver more operating time between recharges.
NOTE: The manufacturer recommends conservative estimates when selecting a battery. More amp-hours will deliver a reserve capacity and a larger capacity battery will not be subject to deep discharges. Ideally, the number of amp hours you expect to use should be less than 50% of the battery's rated capacity.
PROTECTIVE FEATURES
LOW BATTERY ALARM:
An audible alarm will sound when:
1. The 12 VDC power supply voltage drops down to 10.6 VDC. This indicates that the battery needs to be recharged or there is an excessive voltage drop between the battery power source and the inverter.
2. The inverter is overloaded.
3. The inverter is in thermal shutdown.
NOTE: It is normal for the alarm to sound the when inverter is being connected to, or disconnected from, a 12 VDC power source. This does NOT indicate a problem. However, if this alarm sounds continuously, as described, discontinue inverter operation and recharge the battery before resuming operation. If the voltage drops to 10.0 VDC, the inverter will automatically shut down. If the low voltage alarm sounds when the battery is fully charged, refer to the troubleshooting table for possible causes and remedies.
CIRCUIT PROTECTION:
The inverter has electronic circuit protection against overload or short circuit condition.
Vector Manufacturing the makers of the MAXX 1500 power inverter have a web site located at the link below. There are a number of online stores that sell this equipment and you may want to shop there. I got mine at home depot. They ordered it for me and they also stock a 750 watt model. I have the 750 watt unit, I use to charge my laptop, and digital camera. However, it's too weak to run my small coffee pot or recharge my cordless drill. The 1500 watt unit handles my coffee pot, a small miro-wave oven, a tv/vcr combo, and I think it can power our full size refrigerator.
http://www.vectormfg.com/site2/frontpages/company.htm
Contact Vector Manufacturing toll-free at (866) 584-5504 between 9 a.m. and 5 p.m. ET Monday through Friday.
Figure 3 Uninterruptible Power Supply
Common unattended applications for the UPS (floating battery) configurations are for powering: sump pumps, safety lighting, communications equipment, burglar alarm systems and computer systems.
THEORY OF OPERATION
MAXX 1500 inverters change 12 VDC into 110 VAC (110 VAC RMS), electrical power. This is accomplished in two steps. See FIGURE 4. The first stage raises the 12 VDC input to 145 VDC. The advanced design of the DC-to-DC first stage uses modern high-frequency conversion techniques that replace bulky and heavy transformers found in older, less technologically advanced inverters. The output stage changes the 145 VDC to 110 VAC. This solid-state circuitry ensures excellent overload protection and the ability to operate reactive loads such as those found in inductive motors and most fluorescent lamps. The inverter's output stage uses multiple banks of metal-oxide semiconductor field-effect transistors (MOSFETS). This stage functions as a high-power bipolar switch, alternately applying opposite polarity to the AC outlet HOT and NEUTRAL terminals.
Figure 4 Simplified Diagram
The 110 VAC output of the inverter is in the form of a modified sine wave (MSW) as shown below.
This type of waveform has the same energy characteristics as the sine wave of commercial electrical power. The modified sine wave is superior to the 100% square wave output (not shown) produced by most other DC-to-AC inverters on the market. A modified sine wave, as compared to a square wave, is vital to the efficient and proper operation of certain appliances such as computers, TVs, and certain electronic equipment.
Figure 5- Modified Square Wave and Sine Wave Comparison
NOTE: The 110 VAC output is a modified sine wave that produces 115 VAC. Because of wave-shape differences, if you measure the output of the inverter using standard digital or analog voltmeters, these instruments may not correctly read the voltage. Unless a true RMS reading voltmeter such as a Fluke-87, Fluke-8060A, Beckman-4410 or Triplet-4200 is used, the reading will be from 2 to 20 volts low.
OPERATION
NOTE: Ensure that the total continuous power consumption of all tools and/or appliances connected to the inverter (and in use) does not exceed 1500-watts. Also ensure that the start-up wattage for inductive loads does not exceed 3,000 watts for more than a few seconds.
CAUTION: Appliances such as microwave ovens will normally draw more current than they are rated, and could possibly overload the inverter when operating simultaneously with other appliances. For example: A 600-watt microwave oven draws approximately 940 watts.
POWER REQUIREMENTS:
Most electrical tools, appliances and audio/video equipment have labels that show the unit's power consumption in amps or in watts, or both. To avoid inverter shutdown and possible damage to the inverter, take care to avoid exceeding the 1500-watt rating of this unit. If the power consumption of the tool or device is rated in amps, multiply the amps by 110 VAC to determine the wattage.
For instance, a power tool rated at 4-amps will draw 460-watts. The inverter has built-in overload protection so that if you do exceed the 1500-Watt continuous duty limit, the inverter will automatically shut down. Once the excessive load is removed, the inverter can be restarted and resume normal operation.
Note: To restart the inverter turn it OFF, and then turn it back ON to restart. The ON/OFF switch is located on the front panel of the inverter. The inverter powers resistive loads the easiest; however, larger resistive loads such as electric stoves or heaters could draw more wattage than the inverter can deliver on a continuous basis.
The following chart shows the approximate amperage at 110 VAC and the corresponding wattage at 110 VAC for various common tools and appliances:
Appliance Chart
NOTE: APPLIANCE SPECIFICATIONS MAY VARY FROM BRAND TO BRAND. THIS TABLE IS OFFERED ONLY AS A GUIDE TO APPROXIMATE POWER RATINGS. CHECK YOUR APPLIANCE MANUALS OR PRODUCT LABELING FOR ACTUAL RATINGS. TO USE THE MAXIMUM OUTPUT OF 1500 WATTS, MAXX 1500 MODELS MUST BE CONNECTED TO A DC POWER SUPPLY CAPABLE OF PROVIDING 150 AMPS.
Power Output
The inverter will operate most AC loads within its power rating (1500 watts continuous.) Some induction motors used in refrigerators, freezers, pumps, and other motor-operated equipment require very high surge currents to start them. The inverter may not be able to start some of these motors even though their rated current draw is within specifications for this power inverter. If a motor refuses to start, observe the battery voltage using a DC voltmeter while trying to start the motor. If the battery voltmeter drops below 11 volts while the inverter is attempting to start the motor, this may be why the motor won't start. Make sure that the battery connections are tight and that the battery (or batteries) is (are) fully charged. If the connections are good and the battery is charged, but the voltage still drops below 11 volts, you may need to use a larger battery (or battery combination).
Input Voltage
The inverter will operate from input voltages between 10.5 VDC and 15 VDC. If the voltage drops below 10.6 volts, an audible low battery warning alarm will sound. The inverter will shut down if the input voltage drops below 10.5 VDC. This built-in feature protects the battery from being completely discharged. The inverter will also shut down if the input voltage exceeds 15 volts. This protects the inverter against excessive input voltage. Although the inverter has built-in protection against over voltage, it may still be damaged if the input voltage exceeds 15 volts.
NOTE: Exceeding the recommended voltage limits will void the manufacturer's warranty.
Inductive loads, such as TVs and stereos, require more current to operate than do resistive loads with the some wattage rating. Induction motors, as well as some TVs, may require two to six times their rated wattage to start up. Because MAXX 1500 Model inverters have a peak power rating of 3000 watts, many such appliances and tools may safely be operated. The equipment that needs the highest starting wattage are pumps and compressors that start under a load. This equipment can be safely tested. If an overload is detected, the inverters will simply shut down until the overload situation is corrected. Use the front panel switch to turn OFF the inverter then ON to reset the inverter after this shut down occurs.
CAUTION: NO USER-SERVICEABLE COMPONENTS INSIDE. OPENING UNIT WILL VOID WARRANTY.
DETERMINING NEEDED BATTERY SIZE:
To determine the minimum battery size that you will need to operate appliances from the MAXX 1500 Models, follow these steps:
1. Determine the wattage of each appliance and/or tool-you will need to simultaneously operate from the inverter. To do this, read the labels on the equipment to be operated. Usually, power consumption is shown in watts. If it is shown in amps, multiply by 110 AC to determine the wattage.
2. Estimate the number of hours the equipment will be in use between battery recharges.
3. Determine the total watt-hours of energy use, the total running time, and the average power consumption.
To get an estimate of the current (in amps) that the battery must be capable of delivering, divide the load consumption power (in watts) by (10). Keep in mind that most appliances are not operating for long periods of time. For example, a typical home use coffee maker draws 500 watts during its brew time of 5 minutes, but it maintains the temperature of the pot at about 100 watts. Typical use of a microwave is only for a few minutes, sometimes at low power. Some exceptions to brief operating times are lamps, TVs and computers.
BATTERY OPERATING TIME
Figure 6 above shows a set of curves that show how appliance load in watts amperes affects operating time. These curves are only estimates of operating time, dependent upon:
The condition of the batteries
The state of charge on the batteries
The amount of other DC appliances drawing current from the batteries.
Three curves were developed for a battery of 50-Ampere Hours capacity, and three for multiple batteries in parallel. The higher capacity curves are for 120 AH, 200AH and 400 AH capacities. These large capacity batteries clearly extend operating time at full load. To extend operating time, in general, reduce the heavy appliance load to a minimum. Remember, you are operating on stored energy and probably under power loss conditions. All operating time curves assume permanent installation with the correct DC input wire (#2 AWG) and a full charge on the batteries.
The MAXX 1500 series:
1. Avoids the necessity of starting your high operating-cost engine or generator for brief periods of use to operate AC appliances.
2. Provides valuable emergency power for use during utility company power outages. During storm season or peak usage periods when many areas are subject to power losses or "brownouts", you will always have power to operate refrigerators and freezers, keep valuable communications channels open, and generally be self-sufficient until utility power service is restored.
The MAXX 1500 can deliver up to 1500-watts AC output to power an electric chainsaw, heavy-duty drill or big work lights. The inverter can momentarily supply up to 3000-watts of startup power for inductive loads. The Vector manufacturing company produces a number of different power inverters. All Vector inverters have two methods of preventing batteries from being completely discharged. When your batteries begin to drop in voltage, the inverter will sound an alarm. You can either turn off the inverter or leave it unattended. Further discharge will automatically turn off the inverter leaving enough battery charge to crank your engine. If your battery does go to complete discharge, it's because some other appliances are drawing power from the battery. You will only have to crank your engine when you need to move your vehicle or to recharge your batteries. The inverter will supply pure, uninterrupted, quiet and efficient AC from your batteries.
BASIC TOUR OF THE MAXX 1500 MODEL INVERTER
AC power is supplied via three standard North American grounded, household type receptacles mounted on the front panel. This allows the connection and operation of most 110 VAC powered electrical and electronic appliances that use a standard plug.
The rest of the front panel items are:
One combined over-temperature and overload LED. If this lights, the inverter will automatically shut down.
One green LED, that lights when the inverter is operating.
One ON/OFF switch, that shuts off the AC output and all inverter functions.
The ON/OFF switch is also used to reset the inverter after shut down due to over-voltage, overload or over-temperature condition.
Located on the back panel are the DC connectors and fan locations. Note that the fan only operates when the inverter's load requires it to operate. It shuts off when cooling is not required.
SAFETY FEATURES
Built in safety features include:
- Automatic overload and over-temperature shutdown and manual reset (activated if
AC output exceeds 1500- watts for more than a few seconds)
- Automatic AC short-circuit shutdown and manual reset
- Automatic low voltage audible alarm and reset (sounds at 10.6 volts input)
- Automatic low-voltage shutdown and manual reset (activates at I 0.0 volts DC)
- Automatic high-input voltage shutdown (activates at above 14.7 volts DC) and
manual reset
WARNING: The MAXX 1500 output should be treated with the same caution as any 110-volt AC circuit. It is very important that anyone who is installing or using the inverter read and follows all instructions provided in this manual to ensure optimum safety and performance.
The MAXX 1500 inverter is ideal for powering:
TV/VCR combinations
Refrigerator/Freezers
Lights
Radio receivers/Transceivers
Heavy-duty power tools & chargers
Stereo systems
Microwave ovens
Household appliances
Computers and peripheral equipment
Dry and/or wet-and-dry vacuums
Sump pumps
Motors
Air compressors
The MAXX 1500 power inverter uses a 12 VDC power source like those found in 12 VDC motor vehicles or it can be operated using multiple battery configurations with commercial battery chargers. For most heavy-duty applications, a multiple battery configuration and the use of deep-cycle batteries is a requirement.
With installations using multiple batteries, inverters can be operated from one of the vehicle 12-volt batteries, so there's always one battery with adequate charge to start an engine. Other features include a high-surge capability (up to 3,000-watts), which is required to start heavy loads such as motors and other inductive devices.
INVERTER APPLICATIONS
Aside from issues of supplying power to higher wattage appliances, inverters must be supplied with a constant source of high current 12 VDC from a bank of batteries. At full 1500-watt load, the DC input requirements are up to 150 amperes at 12 VDC. Read the following applications and comply with them, and your inverter will give you, reliable service.
WARNING: Never connect the inverter's AC output to a household AC distribution system.
UNINTERRUPTIBLE POWER SUPPLY (UPS)
Inverters can be operated as uninterruptible power supplies that continuously provide AC even if outside AC is interrupted. This type of application continuously operates the inverter from a battery bank, simultaneously replacing the charge on the battery bank with an AC-powered 12vort battery charger. Charging can also be by means of a solar charger system. See FIGURE 3. The charger must be selected to operate continuously and to be able to fully replace the charge on the battery as the inverter operates. In this configuration, the battery "floats" on the DC from the charger, not really supplying power or being charged. When outside AC fails, the inverter continues to power the appliances for the life of the useful charge on the battery bank. When outside AC is restored, the batteries are recharged as the inverter continues to operate. Battery recharging must be sized to replace the average current supplied by the inverter plus a little more current. Another requirement is that the battery rate cannot exceed 10% of the rated Ampere-Hour (AH) rating of the battery bank, otherwise the life of the batteries can be dramatically reduced through overcharging. Most modern battery chargers automatically adjust the charging rate based on the state of charge on the batteries they are charging. For this type of operation, use deep-cycle batteries and avoid charging at too fast a rate.
Did you find what you were looking for? Can I be of help to you? To send comments or questions to Captain Tropic click the "E-Mail" button below.
Bookmark this page!
Thanks, Captain Tropic
