Things that Work! Home Power tests a Sovonics PV panel & the Ovonics Battery tests conducted by Sam Coleman and Richard Perez Since the mention of the Emergency MicroPower Systems (EMPS) in HP#13, we have been buried with requests for more information about a portable, solar powered system for emergency use- primarily communications with a side order of small time lighting. Well, we've come up with a working system that features three new components. One is a fold-up thin-film PV made by Sovonics. Another is a brand new Ovonics nickel-hydride battery that offers high density storage, without toxic cadmium!. The third is the Powerstar inverter ("Things that Work!" this issue). The EMPS This Emergency MicroPower System consists of three basic components: the PV panel, the battery, and the inverter. Also used in the EMPS are a collection of power supplies, cords and adaptors to increase flexibility and utility in portable and emergency situations. This EMPS is a MICRO system. It can power communications devices like radios, and small efficient TVs. It can also power efficient lighting, like the new PL-5 fluorescents (5 Watts input) whose light equals a 25 watt incandescent. The EMPS can also intermittently power high-tech electronics- 120 vac VCRs, video cameras and computer equipment. The EMPS is not designed to power large loads like refrigerators or washing machines. The whole EMPS package weighs less than six pounds and fits easily into a backpack or briefcase. The Sovonics PV Panel The tiny fold-up PV is 19.4" wide, 13.5" tall and 1/4" thick when extended to catch the sun. Folded the PV measures 9.75" wide, 13.5" tall, and about 1/2 " thick (the size of a medium notebook). The panel weighs 2 pounds. The photovoltaic surface is thin-film amorphous silicon , deposited on stainless steel by the revolutionary Sovonics process. The thin-film PV is in a vinyl case with large grommets at the corners, very handy for securing the panel. Electrical access is via a polarized SAE connector, cord and male cigar lighter plug, all supplied with the panel. We inadvertently left the panel outside during bad weather, the rain and freezing did it no damage. We just hung it up inside to dry out. The cost of this panel is $143. Electrically speaking this panel produces 6 Watts (0.430 Amps at 14.5 VDC actually measured) under full sun. In a reasonable solar location, this micro PV panel will produce about 35 Watt-hours daily. The Ovonics Nickel-Hydride (NiH) Battery Nickel-hydride batteries are revolutionary variations of nicads. Instead of using toxic cadmium for the cell's cathode, Sovonics uses non-toxic metal hydrides. The resulting cells have about 75% more electrical capacity than a nicad of the same size and weight. The nickel-hydride cells have no memory effect. Small nicad batteries made by the "sintered plate" process display a memory effect. This means that if you don't regularly use all the power from the nicad cells they will lose capacity. This memory effect is not found in pocket-plate nicads, only the smaller sintered plate cells. Nickel-hydride batteries do not display memory effect and retain their capacity regardless of cycle regime. The pack we tested was composed of ten NiH cells in a series string, encapsulated in a plastic box. The resulting battery is a nominal 12 VDC pack with a rated capacity of 3.4 Ampere-hours (Å44 Watt-hours of power storage). The cells are in a standard "C" sized flashlight cell format. Electrical access is via a female cigar lighter plug on a short wire pigtail. The Ovonics battery pack is 6.5" long, by 3.25" wide, and 1.5" tall. It weighs 2.5 pounds, complete with case, cord and connector. Cost for this high-tech storage system is $186.27, about 40% more expensive than using sintered plate nicads of the same Ampere-hour capacity. We think that the additional cost of this battery is justified by its high capacity and low weight- just what is required by an EMPS. We immediately went to work charging and discharging the Ovonics NiH cells. We first selected a brutal discharge rate of about C/1. This means that we emptied the entire pack in less than an hour. As a test setup we used a 40 Watt, 120 vac, lightbulb plugged into the Powerstar inverter fed by the Ovonics NiH battery. All measurements were made by a Fluke 87 recording digital multimeter. The actual average discharge current for this test was 3.87 Amperes or a C/0.93 rate. The actual capacity we obtained was 3.6 Ampere-hours, more than Sovonics rates the pack! The voltage vs. time curve for this ÅC/1 rate appears below. INSERT ART1 We then tried a more civilized discharge rate of 0.58 Amperes or C/6.4. Actual tested capacity was 3.74 Ampere- hours. This is 0.34 Ampere-hours more than rated and about 87% more capacity than a sintered plate nicad pack of the same size. The voltage vs. time curve for the C/6.4 discharge rate is shown below. These new Ovonics NiH cells are hot stuff! In its charge and discharge cycles, the Ovonics NiH cells behave much like the sintered plate nicads. Voltage and current curves are much the same and the NiH cells can be used interchangeably with nicads, the only difference is vastly greater capacity. INSERT ART2 Not only does the NiH battery offer better performance than sintered plate nicads, but it's environmentally safer because it doesn't use cadmium. Many states and the federal government are considering a deposit on toxic batteries (up to $1 per cell). NiH batteries offer increased performance and savings, not only for our pocketbook, but for the planet. Sovonics is now working with cell prototypes that will increase the capacity of the Ovonics cells. In the future, the NiH cell technology may be developed to the state that we'll be using them in home systems and electric vehicles. The smaller sizes are available now. The Ovonics NiH cell is a working reality. Other EMPS Components In order to make an EMPS flexible and useful, a variety of other components should be included. The first is a power supply that will recharge the Ovonics battery from a 120 vac source. We used a small wall cube that produced a solid 0.5 Amperes at 14.5 VDC into the Ovonics pack. This supply functions well on either grid or inverter. The second power supply we included is a DC/DC converter/regulator that allows the PV panel to directly power radios, tape recorders, etc. without any battery in the system. This is handy if you want to run something and the battery is discharged. The DC/DC converter comes with an assortment of DC power plugs that will fit just about any device. The last EMPS accessory is a set of two female cigar lighter plugs wired in parallel with a single male cigar lighter plug. The "Cigar Y" allows the system to be simultaneously charged and discharged. System Performance The EMPS is a totally solar powered system capable of cycling about 27 Watt-hours daily. It interfaces directly with automotive systems. For example, the PV panel can recharge a car battery & the car battery can power an inverter or recharge the portable Ovonics pack. And the system is still capable of total stand-alone solar operation! The performance of this collection of EMPS hardware is entirely dependent on the user. The user selects the appliances (loads) that will be run from the system. If you select an efficient radio and light, then the system works well. For example the EMPS will supply enough power for continuous operation of a radio receiver (0.6 Watts) and about three hours of lighting daily with a PL-5 fluorescent. For city folks, the EMPS can be stored in a small box until needed. When commercial power fails, it is ready to go, providing essential communication and lighting. The EMPS also makes an excellent, lightweight, portable micropower system for backpackers, aviators, and boaters. The EMPS is also a very effective demonstrator. The EMPS contains all the same components found in larger home power systems- the only difference is proportion. This makes the EMPS an ultrafine educational tool. Access- Complete EMPS We have a problem here. The concept of this EMPS and several of its components are so new that few companies offer a complete working EMPS package. None offer this particular EMPS for sale. Electron Connection Ltd. has decided to offer a complete EMPS for sale via mail. This EMPS consists of a 6 Watt Sovonics PV micropanel, Powerstar inverter, Ovonics NiH battery pack,an ac charger for the battery, a DC/DC converter, a "Cigar Y", and all the plugs, cables and connectors detailed in this article. Electron Connection will ship this entire EMPS package, postpaid, anywhere in the USA for $465., add $25. for shipping outside USA. Contact: Electron Connection Ltd., POB 442, Medford, OR 97501 or call 916-475-3179. Access- EMPS Components Sovonics (makers of the PV and Ovonics battery) 1100 West Maple Road Troy, MI 48084 313-362-3120 Harding Think Tank 633 Washington Grand Haven, MI 49417 616-847-1966 Alternative Power & Light Rt3, POB 128 Cashton, WI 54619 608-625-4123 Backwards to the Future Rt1, POB 225 Pullman, MI 49450 616-236-6179 Lake Michigan Wind & Sun E3971 Bluebird Rd. Forestville, WI 54213 414-837-2267 Sunlight Energy 2225 Mayflower, N.W. Dayton, OH 45420 513-832-3114 Solar Technologies 1725 Sugar Creek Trail Greenfield, IN 46410 317-326-2440