Battery Containment Dear Home Power People; Thanks very much for answering my previous letter in HP #29. I guess I didn't make it clear that I wanted information about specifically what materials are unaffected by battery acid? Fiberglass, PVC, ABS? I would hesitate to put batteries in Tupperware containers, as you suggested, without being absolutely certain that the plastic was in fact completely resistant to battery acid. My system has only two golf cart batteries which I have since put in plastic boxes made for boat batteries (cost $7 each at K-Mart). Seems safe to assume that these boxes are acid resistant. The golf cart batteries are taller than what these battery boxes were made for, but the boxes will at least contain possible leakage and the covers keep dust off the battery tops. Admittedly, battery gassing is not externally vented. Perhaps external venting would not be necessary with Hydrocaps? My maximum charge rate is 6 or 7 Amps on the 220 amp-hour batteries. People with larger batteries indoors may want to make battery boxes from scratch. Perhaps you could discuss chemical properties and reactions regarding battery acid and different materials for containment. Sincerely, Clive Ellis, 2039 Manzanita St., Klamath Falls, OR 97601 OK, Clive, here is a table showing the chemical resistance to electrolytes (both acid and alkaline) for various commercially available plastics (info courtesy of The Handbook of Chemistry and Physics). It looks to me like the best and most obtainable plastics to use are polyethylene or polystyrene. Both are virtually inert under attack by electrolytes. Ä Richard. INSERT TABLE Auto Charging Dear H.P. Crew; I have run the full gamut of trial and error as far as A.A. To D nicads go. First, I bought "el cheapo" with too small a capacity to last very long. Then I fried a couple of good ones in a solar charger. I forgot! Now I'm reading with great interest how you folks use them all of the time and have their recharging down to a science. You even give detailed specs on how I can build my own that will make them last longer. Well I don't want to build my own! I don't have the time or desire. I'm a craftsman/artist. I don't do electronics. I have been using 9.2 volt nicads in portable tools for years, and they're great. I think the problem with the smaller ones is that I haven't yet found the perfect auto shut off charger. So.....Who makes the best, idiot proof charger for the non-teckies out there. I know I'm not alone. Look forward to your reply. Gratefully yours, Paul Christopher Prelitz, POB 5024, Laguna Beach, CA 92652 ù 714-494-6353 Well, Paul, the reason we build our own chargers is that every commercial model under $200 is less than perfect. The nicad pulsar we featured in HP#30 is cheap and simple to build. It will run rings around any commercial charger. If you don't want to build it, then find a techie and pay him to build it for you. How about it techie readers, anyone want to build a pulsar and sell it to Paul? Ä Richard Electric Mower Dear Richard Perez: In Home Power #30, reader Noel Perrin asks for a source for battery-powered electric lawnmowers. Here is a source: Kansas Wind Power, Route 1, Holton, KS 66436. They sell various models of Elec-Trak lawn and garden tractors, new and used, in prices ranging from $750 to $3200. Any of these small garden tractors can be used as a rider-mower. I should point out that these Elec-Trak tractors are apparently manufactured by General Electric. I strongly urge Home Power readers to respect the ongoing boycott of G.E., which has been heavily involved for years in all kinds of weapons production, especially the production of nuclear weapons. Nuclear weapons continue to threaten all life on earth, in spite of the end of the Cold War. Sincerely, Martin Holladay, POB 72, Sheffield, VT 05866 Battery Housing Gentlemen: One of the things that bothers me concerns batteries for PV panels. On one hand, batteries need good ventilation and separation from the house. On the other hand, batteries must not be allowed to freeze, or to get too hot. These requirements seem to me to be contradictory. Can you help me on these questions? Our home will be at 5300' and 33 N. latitude. John Gordon, 2828 Quay Loop, Holloman AFB, NM 88330 ù 505-479-9043 Hi, John. Zomeworks Corp builds a temperature controlled box for batteries called "Cool Cell". This box is a passive device and requires no electricity. While I've not tested one, I hear good reports from users in hot climates. The box will keep batteries form overheating in the summer and from freezing in moderate climates during the winter. Ä Richard Sun & Suds Dear Home Power; Please send me one copy of Joseph Radabaugh's HEAVEN'S FLAME. Our new "Sun Oven" really cooks, even here in the cloudy great Lakes region. The book is for my mother, who became an instant convert to solar cooking after a Sun Oven demo. One question: do you - or any readers out there- know of a Canadian source for the James washer? Could you possibly print this question, including the address below in your mag? Thanks. Wendy & Wolfgang Weiss, RR #3, Parry Sound, Ontario, P2A 2W9 CANADA OK, readers, can anyone help Wendy and Wolfgang out? How & Why My friend has been generous in lending me his back issues of Home Power, The problem is that they're so handy to have as reference that I hate to give them back - hence my large purchase of back issues. I have 24 Arco M-53s, Trace 24V inverter, Heliotrope CC 60-C controller, Cruising Equipment Amp meter, Exide lead acid battery bank, Flowlight slow pump - good stuff. But none of these manufacturers offers more than a description of how their equipment is supposed to work. For real insight into the quirks and actual performance of these things, your magazine is excellent. A good example is the manual for my Heliotrope CC 60-C. It provides no real detail on how the device actually works. They describe how the controller regulates the "energy" and "output" of my PV modules. Kind of vague! I'd like to know what the controller is doing to the voltage and amperage of my PVs. What kind of readings should I expect to see on the volt/amp meter at various times in the charge cycle? The Trace manual, though very good, only hints at the limitations of a modified square wave inverter in the operation of things like fan motors. I have a nice propane furnace that I'd like to use, but the blower motors and transformer say "no way" when asked to run on inverter power, any suggestions? Sincerely, Eric Mellen, 11500 W Sinagua Rd., Tucson, AZ 85743 ù 602-449-4072 Hello, Eric. The Heliotrope controller works by rapidly switching the array on and off. There is a transistor (or two) in series between the PVs and the battery. This transistor is rapidly activated to provide the battery with a regulated voltage when the voltage set point of the controller is reached. Your voltmeter will show whatever voltage you have set on the controller when it is regulating. The current (Amps) from the array will vary depending on what the battery wants to accept at that specific voltage set point. As the battery fills, the amount of current delivered by the control decreases. This basic scheme is called Pulse Width Modulation (PWM) and has been proven to be the most effective way of controlling PVs that are recharging a battery. With regards to the furnace motors, contact Jim Forgette at Wattevr Works! about a replacement motor that will run on your inverter. Or replace your mod sine wave inverter with a pure sine wave type like Dynamote's Brutus reviewed in this issue. "Pulsar" Recharge Dear Chris; I just read issue #30 and read the article on "Pulsar". Could you advise how a similar unit could be used to recharge a battery bank? I think this current train may be useful in eliminating similar problems in recharging small nicads as well as larger batteries. If you could supply any additional info I would greatly appreciate it. Thanks, Chris McKay, POB 991, Maywood, NJ 07607 Dear Chris: Using pulses to charge big battery banks is not a bad idea, but to do it through the whole charging cycle without wasting precious energy from your renewable energy system would be difficult. Besides, lead acid batteries and pocket plate nicads don't suffer from the memory effect and dendrites that sintered plate 'flashlight' nicads suffer from, so charging with pulses really doesn't buy you much. The Pulsar uses high frequency switching to lessen the current from a big battery bank to charge 'flashlight' batteries. Lots of current flows when the switch is on, nothing flows when it is off. The average - the current your flashlight batteries receive - is somewhere in between. With the Pulsar, when the switch is off the electricity stays inside your house battery bank. If you wanted to use high frequency switching to charge your house-size battery bank, you would be rejecting power from your solar panels or wind machine. In this case rejected power is lost power. It doesn't stay around in the solar panels or the wind machine, it's gone if you don't let the battery absorb it. In the bulk of the charging process you want all the power you can get from your renewable energy system. But when the battery is nearing full, reducing the current, even if it means rejecting the rest, is not a bad idea. Indeed many available charge controllers use high frequency switching for controlling the charge on house sized battery banks. Brand names include: Heliotrope CC20, CC60, and CC120, the Enermaxer, and the Bobier ECM1 unit for their LCB.- Chris