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We figured that most folks would want a battery that had the cranking amps to easily spin the starter and would not care much about the a-hrs. The cost is directly proportional to the amp-hrs. If we were to go to 16 amp-hrs (it's easy to do) the cost would go up to about $850. The cranking amps would also go up in proportion too. Figure about $1 per cranking amp, and about $50 per amp-hr and you won't be far off. The steps are 2.3 a-hr and 120 cranking amp increments. You pick. This battery REALLY spins the starter in my GMC van. When I turn on the key in the morning, the battery voltage is typically 13.4 volts (instead of 12.8 volts.) Anyone in the Denver area that flies daily interested in flight testing one of these? You would get to keep the battery and write anything you want about it (good or bad) as long as it was truthful. You would have to inspect it before and after each flight including noting the voltage and the BMS indicator light status. You must sign the usual liability waiver we are all now accustomed to of course. :-) I'd flight test it myself, but I'm still building the wings on my RV-7. ;-) Bill Dube' bike@KillaCycle.com At 10:05 AM 2/6/2007, you wrote: That is indeed impressive, Bill. Weights about 10 lbs less than the Odyssey PC680, equivalent cranking amps, bit more voltage, so a bit better power, only 5 A-hr less than Odyssey. So looks like you could double the weight 7.4 lbs and have MORE A-Hr and still 1/2 the weight of the Odyssey. If I were to make a suggestion, it would be to look at the marketing advantage of having more A-hr than the Odyssey at 1/2 the weight (If it scales that way). The aircraft market and racers are probably two areas that would be interested in that kind of weight savings at that price. Just my 0.02 Ed ----- Original Message ----- From: "Bill Dube" <billdube@killacycle.com> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net> Sent: Tuesday, February 06, 2007 11:21 AM Subject: [FlyRotary] Finally built - 3.7 lb, 600 cranking amp, 11.5 A-hr battery Well, I said I was going to do it and we finally got the prototype built. We just built a 600 cranking amp, 11.5 A-hr, battery that weighs just 3.7 pounds. I've been testing it in my GMC van for the past week here in the Denver Winter. It snaps the van right over every morning without a problem. The van cranks faster than it did with the standard lead-acid battery. It is smaller than the Odyssey 680 so it fit in the same battery box with a couple of foam blocks for spacers. The battery has four status LEDs that tell you the cell balancing electronics are working OK. We are using A123 Systems M1 cells with our own custom battery management electronics. The A123 Systems cells are proven to be the safest Li-Ion cells on the market. No problems with fires (like laptop cells) because the chemistry they use is completely different. The battery can be damaged by running it completely flat (like leaving the master on) and holding the battery below 8 volts for a long time. It can also be damaged by charging it over 15.0 volts. It will likely still function after such abuse, but it won't be nearly as good as it was originally. If you don't abuse it, it should last you for many years. I think we will be in production in about a month, maybe two. Specs: 3.7 lbs 600 cranking amps 11.5 amp-hr Approximate maximum dimensions: 3" wide, 5" long, 7" tall (including terminals) Charging voltage = 13.8 to 15.0 volts (anywhere in this range is OK) Nominal voltage = 13.2 volts (Just a touch higher than your typical lead-acid, so it spins the starter a touch faster.) Cell cycle life rated at 2000 cycles (80% DOD, 90% capacity remaining) 10,000 cycles (80% DOD with 50% capacity remaining) @25 C Cell specs: <http://www.a123systems.com/html/products/ANR26650M1specs.pdf>http://www.a123systems.com/html/products/ANR26650M1specs.pdf Maintenance free No heavy metals (iron-phosphate type cells) At this time, we estimate the retail price will be $595. (Yeah, I know this is not cheap, but this is the state-of-the-art battery technology so the parts to make it are not cheap.) Here is a picture of the prototype. We have it in a clear Lexan case so we can keep an eye on it. The production battery will have a smaller opaque case with a clear top lid (terminal end.) http://www.killacycle.com/photos/aircraft-battery/Prototype1InVan.JPG We have been racing these cells in the KillaCycle for about a year, so we know _all_ about them. <http://www.KillaCycle.com>http://www.KillaCycle.com (Be sure to watch the movie clip.) Bill Dube' <mailto:bike@KillaCycle.com>bike@KillaCycle.com -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/