From: John De Armond Newsgroups: rec.outdoors.rv-travel Subject: Battery Myths Date: Fri, 15 Aug 2008 05:22:26 -0400 Message-ID: <7kiaa49dhlv8akgdmur771s6a7s3q18mo4@4ax.com> Here is an interesting paper by an engineer at SAFT, one of the international major battery manufacturers. It dispels many myths that are floating around about battery banks. http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf John From: John De Armond Newsgroups: rec.outdoors.rv-travel Subject: Re: Battery Myths Date: Sat, 16 Aug 2008 20:28:50 -0400 Message-ID: <l9qea4d4pr7qs2oi38bi5jdkurbhfjt5go@4ax.com> On Fri, 15 Aug 2008 17:00:11 -0700, Gar <olgar2@myrvspace.com> wrote: >John.. could you summarize what he said for me/us??? I read about 2 >paragraphs and knew it was waaaay over my head... Easy. Pretty much every bit of conventional wisdom about batteries in series or parallel not working is myth. Batteries can be operated in parallel, series or series-parallel without problem. Unequal size batteries can be operated in parallel. Batteries of different ages can be operated in either series or parallel. A bad battery in a series string can be replaced without problem. Tom J: That paper is just as applicable to your series/parallel 12 volt system as it is to a 500 volt system. You have 12 cells. It doesn't really matter how they're divided into physical cases. These myths are perpetuated by the many "experts" on the web, few if any have ever tried what is supposed to be so bad. Few, if any, have ever been around industrial battery banks either. I learned about battery truths first by being the responsible plant engineer for several large (250 volts, approx 100,000 amp-hours) standby battery banks in a nuclear plant and later, by simply trying things on my own. TVA sent me to a nice school on battery management and I paid attention. Others learn the same thing in similar ways. Off-gridders have a bad battery and out of financial necessity, replace only that battery instead of the dozens of batteries that may comprise their bank. When everything works fine, the light comes on, so to speak. EVers find out about replacing a weak battery in a series string pretty much the same way and for the same reasons. Yet the myths persist. I very much doubt that a paper written by a major battery company engineer and presented to his peers will have any effect on the myths but I thought I'd pass along the info anyway. Incidentally, here's an ancient book on batteries that is still highly relevant today http://books.google.com/books/pdf/Storage_Batteries_Simplified__Operating_.pdf?id= The book talks quite a bit about Edison or Alkaline batteries. These are now more commonly known as nickel-iron batteries. Absolutely wonderful batteries that got pushed to the side, mainly by Edison's greed. 100 year old batteries that Edison's company built are still in service, still at full capacity and still having an indefinite life expectancy. Chrysler used them in its experimental TEvan electric van but otherwise, they've been ignored. As usual, the ChiComs are filling the void. There is currently one importer of ChiCom NiFes and he's being greedy too. As soon as the second importer comes on board... I'm looking forward to being able to buy my first and lifetime supply of NiFe batteries for my RV sometime in the near future. The only "problem" with NiFes is that they use a goodly amount of water. Gassing is part of their normal operation. Most modern batteries (the Eagle Picher batteries in the TEvan for example) have automatic watering systems. That turns it into no big deal. Just add some distilled water to the tank occasionally and otherwise forget about 'em. One other brief comment. The book talks about the Delco 32 volt lighting plant. My great-grandfather has one of those on his fairly large farm in Alabama. I recall it from my childhood. He held out when TVA and the REA came to town, considering them to be yankee meddling and/or communism, depending on which mood he was in :-) The lighting plant actually worked very well. Automatic start and stop, based on the state of charge of the battery bank as measured by an electromechanical amp-hour meter (similar to but better than an E-meter). Smart charging similar to what we do today, only implemented with relays. A high enough voltage to avoid having to run very large wiring but low enough not to present a shock hazard. He ran his house, the dairy barn and the milking parlor on the system. He did operate it on manual, however, thinking that he could manage his batteries better than that fancy automatic control (probably because he didn't understand it.) He'd crank it in the morning and run it until it cut off. One of my most vivid memories from that time was watching him listen to his 32 volt Delco radio in the evening. Often as not, the batteries would be near exhaustion. As the volume decreased with the dropping voltage, he'd move his chair closer and closer to the speaker until at the end he had his head half-way in the speaker :-) When he died, great-granny had it all replaced with "government power". And then took great offense when they "dunned" her. That is, sent her the first power bill :-) I sure wish she'd tucked all that stuff away in a barn somewhere. Delco plants in working order are worth a bundle these days. Another example of the old saying, "There really isn't anything new under the sun". John |