Welder I would like to know how to make a welder from a car or truck alternator or just from a deep cycle battery. We that use alternative energy usually don't have power enough to operate a transformer welder. Thank you so very much, Jim Carr, Rt #2 Box 475A, Rush, KY 41168 The MigMaster DC Welder is powered by 24 Volts DC (See Things that Work in issue #30). The manufacturer specified current consumption is 200 Amps - though this depends on the type of welding being done. "MIG" stands for "metal inert gas". A gas such as argon or carbon dioxide is injected at the welding tip to displace oxygen and cool the welding tip, allowing 100% duty cycle operation. It costs $249 for a basic unit or $599 for a toolbox model that comes with batteries and an electric drill for wire feeding. Distributor (Western U.S.): On Line Marketing, Inc., 12315 Mukiteo Speedway Blvd. Bld.1 , Ste. 2, Lynnwood, WA 98037 ù 800-743-1403. ÄAmanda Hi, Jim. You can weld with just about any battery with a voltage greater than 24 Volts and a capacity of greater than 100 Amp-hours. Control the current by using a heavy rheostat. A car alternator is far too small to be an effective welder on anything but light sheet metal. Ä Richard Wire We Here I plan to wire my new home 12V. Does it make sense to convert 120vac to 12VDC until I purchase the other equipment (PV, wind, etc.)? Would this be done by battery charger to batteries, then the batteries to DC load? What charger should I use? Is this possible? I welcome your advice. Chris McKay, POB 991, Maywood, NJ 07607 It is possible to convert your house to 12 VDC, but why would you want to? 12 Volt DC requires thick expensive wires, and 12 Volt appliances are more expensive, harder to get, and are poorer quality (in general) than regular 120 vac appliances. For this reason most renewable energy homes these days use inverters. It's great to hear you're planning to make your (currently grid connected) house renewable energy powered. Starting with batteries and a charger is an option, and it would give you power during blackouts. Keep in mind, though, that a lead-acid battery's life is limited to about a decade. No sense sinking a lot of money into batteries if you won't be able then to afford solar panels for five years. There's something to be said for starting with a small complete system to power part of your house, and expanding as you learn. Also we're particularly interested in line intertie systems which feed into the grid. See Mick Sagrillo's article in this issue. Ä Chris Traveling PCs We publish a newsletter for people who travel with their computers and there seems to be a problem with running the computers directly from the generator and other problems concerned with the transformers being plugged into circuits fed by inverters. Can you shed any light on these topics? Judith L. Ashford, 919-D La Mesa Terrace, Sunnyvale, CA 94086 Old funky generators can put out nasty power, with unstable frequency and poorly regulated peak and rms voltages. Computer power supplies Ä especially "switching supplies" found in recent computers Ä are built to take fairly ugly power. The answer is to use an inverter. Inverters these days all have excellent frequency regulation, and the rms voltage regulation is good enough for computers. Besides, most generators are overkill for the power consumption of a computer. Generators are most efficient when they are well loaded. You'll burn less gas if you run the generator to charge the batteries, and then run your computer from an inverter. It's also a lot quieter! We've had excellent success running computers (Apples, IBMs, etc.) from all inverters sold in our market. Laser printers are the only computer peripheral which don't digest inverter power. They use thyristors in their power supplies which burn up when fed the square shaped pulses of "modified sinewave" inverters. Transformers resist the rapid changes in voltage which occur in the waveform of modified sinewave inverters. In our experience transformers fed inverter power just buzz loudly. A solution to inverter/transformer problems is to plug in a "line-tamer" or ferro- resonant transformer between the inverter and the troublesome transformer. Or try a long extension cord wrapped around a piece of iron pipe. These smooth out the waveform at the cost of additional power consumption. An excellent option is to buy a sinewave inverter Ä their power is just like downtown, only better. Ä Chris Pump Problem Dear HP Crew; Our system is inverted by a Trace 2524 SB, ACTC, DVM which is fed by an ample 745 Amp-hr (20 hr rate) battery. Our problem arises with our submersible pump. If the inverter is already on with at least a 150 watt load and the pump pressure switch contacts close, the system pumps as is normally expected. But if the inverter is in idle mode or active but with less than a 150 watt load, the breaker in the service panel clicks off. We contacted Steve Willey and proposed the problem to him as we heard that he had a solution for this problem. He promptly returned an answer stating that some pumps need full power available to them, the instant the contacts close, to start them. They can't wait for the Trace inverters to soft start, thus they surge off and on till the breaker blows. Steve has cured this problem on some pumps by installing a priority load that comes on when the pressure switch contacts close followed by a timer that runs for about 5 seconds and then starts the inverter before activating the pump. He said he had not heard of the partial preload requirement and thus was unsure if the switch he builds would help. So before I try to build another circuit with a load and timer in the pump circuit, I was wondering if any of you had any ideas. Clint & Karen, Box 94, 150 Mile House, British Columbia, Canada VOK 2GO ù 604-296-4592 Inverters have a difficult time starting large inductive loads (such as pumps) from zero load. Steve's circuit which first activates a small resistive load gives the inverter time to get up to its rated current and voltage before the pump is turned on. The problem may be that without the resistive load, the motor of the pump is not receiving a high enough voltage. It may be acting like a short circuit and shutting off the breaker. The problem may also be due to the phase difference of the current and voltage. Current and voltage in purely resistive loads are in phase. The current leads the voltage by 90ø in inductive loads. A load which is both resistive and inductive, such as a pump, will have the current and voltage out of phase between 0-90ø. When the current and voltage are out of phase, the inverter needs to supply more current for a given voltage to give the same amount of power to the load (since P=IV, power equals current times voltage). This may also be the cause of the high current that is shutting off the breaker. The 150W resistive load helps bring the current and voltage back in phase - thus lowering the current supplied by the inverter. A capacitive load will work even better at bring the current and voltage back in phase. If you have a capacitor-start motor and it is above ground, the best solution would be to replace the capacitor with a lower value. Your problem may be due to one of these problems or a combination of the two. - Amanda ABCs A) In #30 page 107, you show a number of shunts. What do they look like and do they cause a voltage drop? B) #22 page 29, What makes a fuel cell work? Is it heat? If so where is the energy for the heat coming from? Also, please show a picture of a fuel cell, it was vacant from the rack when picture was taken for #22. C) If every home in the city had a PV system with batteries wouldn't all the batteries become another environmental problem? I would like to see more about synchronous inverters written about in #29 page 28. D) You have a fine magazine. I am learning a lot from the articles on systems people have built. I would like to see more pictures and diagrams though. Ken Kruller, 6355 137th NE #305, Redmond, WA 98052 A) A shunt has a known small resistance. The voltage drop measured across a shunt can be used to determine the current; current equals voltage divided by resistance (V=IR). Shunts come in all sizes from the size of a Bic lighter (ten Amps) to the size of a Twinkie (500 Amps). B) A hydrogen fuel cell combines hydrogen and oxygen to form water; the resulting energy is released as electricity. An electrolyte (usually a solid polymer membrane) is located between the electrodes. Hydrogen is supplied to the fuel cell at the negative electrode (the anode); oxygen is supplied at the positive side (the cathode). The anode reaction is: H -- > 2H+ + 2e-. Hydrogen dissociates in the presence of a catalyst (platinum is often used), forming hydrogen ions (protons) and giving up electrons to the anode. The hydrogen ions pass through the membrane to the cathode and react with oxygen to form water. Electrons can not pass through the solid polymer electrolyte. The electrons that are released at anode, flow through wires to an external load and then to the cathode where they become part of the cathode reaction which produces water. The cathode reaction is: 2H++2e-+1/2O2 --> H2O .The overall fuel cell reaction is: H2+1/2O2 --> H2O. See The Hydrogen World View by Dr. Roger Billings for more information. C) Batteries could become a big environmental problem if every home used them as their primary source of energy storage. Lead and cadmium are toxic materials that must be properly recycled. Of the current battery technologies, nickel-iron batteries are the least toxic. Synchronous inverters are one solution to this problem (See "Utility Intertie Systems" in this issue). Hydrogen offers another, very clean option for energy storage (see hydrogen article in this issue). ÄAmanda D) Hi, Ken. More pictures and more detailed schematics? See page 99 this issue. Ä Richard