Things that Work! Home Power tests the Powerstar Inverter tests conducted by Sam Coleman and Richard Perez When we unpacked the Powerstar inverter we were surprised. Could an inverter this tiny really put out 200 watts? Don't let the small size fool you, it's a midget powerhouse wherever you need 120 vac from a 12 volt battery. The Powerstar The inverter was heavily packaged and arrived in good shape via UPS. The only documentation was a specification sheet. The Powerstar is so simple to use we didn't need instructions. Only two connections are needed, both plug- ins. One is the inverter's DC input via a male cigar lighter plug. The other is the inverter's 120 vac output, via a single standard ac female socket. The Powerstar is 5" long, 2.6" and 1.7" tall. It weighs 15 ounces. Its case is a beautiful piece of extruded, anodized aluminum and is the inverter's heatsink. The supplied DC cord is 18" long and made from 16 gauge wire. There is a small neon indicator that shows when the unit is making 120 vac. Test Situations We tested the Powerstar on a variety of batteries in two systems and the Ovonics battery as a portable test. The inverter was powered by both lead-acid and large nicad batteries. We used a variety of loads, from incandescent lightbulbs to coffee grinders and computers. Electrical data was taken with a Fluke 87 recording digital multimeter. This meter allowed us to detect the true RMS voltage of the inverter, its positive & negative peak voltages and frequency. Test Results We ran a variety of loads and took data on the inverter's performance. No load power consumption was measured at 0.24 Amperes at 12.60 VDC, about 3 Watts. The various load tests and a graph of the inverter's efficiency appear below. INSERT GRAPHIC It's apparent from the table that the inverter is capable of producing its rated 200 watts. We were able to sustain this 200 watt level for more than 5 minutes without the inverter shutting down. We then added an additional 40 watts bringing the total output up to 240 watts. After about 5 seconds the inverter shutdown (as it should) and protected itself from overload damage. We were able to sustain the manufacturer's rated continuous wattage of 140 watts indefinitely. We would rate this inverter at a solid 140 watt output. The peak voltages were very stable until the inverter was overloaded, then they dropped off. The RMS (Root Mean Square or average ac) voltage remained constant throughout the test. The inverter's frequency stayed around 59.5 cycles per second (Hz.), within specs. Efficiency is slightly less than the 90% claimed by the manufacturer. Our efficiency figures show the inverter ranging from 74% efficient at 10 watts output to 79% at 140 watts output. Peak efficiency was reached at between 25 and 100 watts output where the inverter is about 86% efficient. The inverter refused to die from repeated overloading. In our test the Powerstar functioned properly (rms voltage, peak ac voltage and frequency all within spec) with a battery voltage as low as 9.6 VDC. The Powerstar ran all the test loads without problem. This included a variety of inductive loads using motors and power supplies. We had enough faith in the Powerstar to plug in over $4,000 worth of Macintosh computer equipment and rock-n-roll! The Powerstar ran a Mac SE with a hard drive and the Hewlett-Packard DeskWriter (300 dpi) jet printer with no problems. Conclusions With a price tag of $149.95, the Powerstar offers incredible value in a midget portable inverter. We see many applications where folks want to run a 120 vac appliance from a vehicle or portable battery. The list of appliances that the Powerstar will run is endless- just about anything under 150 watts, indefinitely. The Powerstar opens new vistas of instrument, video and computer use from either portable or vehicular systems. Access Powerstar Inverter Manufacturer Powerstar Products Incorporated 10011 North Foothill Blvd. Cupertino, CA 95014 408-973-8502 Dealers interested in stocking the Powerstar please contact: SunAmp Power Company 8502 East Cactus Wren Rd. Scottsdale, AZ 85253 602-951-0699 Single Powerstar inverters available from ($150 shipped postpaid): Electron Connection Ltd. POB 442 Medford, OR 97501 916-475-3179 and from other Home Power advertisers.