X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [140.172.240.5] (HELO al.noaa.gov) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1064410 for flyrotary@lancaironline.net; Mon, 10 Apr 2006 16:33:51 -0400 Received-SPF: none receiver=logan.com; client-ip=140.172.240.5; envelope-from=william.p.dube@noaa.gov Received: from [140.172.241.126] ([140.172.241.126]) by al.noaa.gov ; Mon, 10 Apr 2006 14:33:06 -0600 Message-ID: <443ABFF4.10303@noaa.gov> Date: Mon, 10 Apr 2006 14:28:36 -0600 From: Bill Dube Reply-To: william.p.dube@noaa.gov Organization: NOAA Aeronomy Lab User-Agent: Mozilla Thunderbird 1.0.2 (Windows/20050317) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: State-of-the-art airplane battery References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Rcpt-To: Ernest Christley wrote: > Bill Dube wrote: > >> The cost will scale directly with amp-hrs. Figure $50 an amp-hr. The >> cranking amps scales as $1 per amp. There are discrete increments. >> 2.2 a-hr and 120 cranking amps. > > > I think you're on the track of a good product, just like with your > LED lights, but since you present this as a market survey I'm going to > lay out how I work through it. > > It comes in 2.2ah increments at $50 each. I'll need at least 20ah at > a 1 hour discharge rate to keep the engine running. I'm assuming all > the cranking amps come from low internal resistance, so power delivery > will be less dependant on discharge rate (?). Total energy delivery is only weakly dependent on discharge rate. > For the standard flooded battery, I'm going to have to look at a 30ah > battery weighing in at around 30lbs and $80, where I could get away > with 22ah of this new technology weighing in at 6.75lbs costing $1,000. Correct. > The conventional battery would need replacing every two years, so the > cost over 10yrs would be $400 vs $1000. I'd most likely loose some or > all of the weight advantage from having to add lead to the tail for CG > purposes (most of the Delta builders seem to wind up having to do > that). But assuming that I got the full weight savings and the > battery would really last for 10yrs, that is 23lbs for $600, or $26/lb. > It sounds like a winner. Now the questions are: > -Can I trust new technology to work as advertised for 10yrs in a > highly stressful environment? Yes. > If it has to be replaced in 5 or 6 years due to any number of reasons > from simple environmental stresses resulting from poor installation up > to and including a landing accident, then the ROI disappears. If you run it to zero volts or to very high voltage, it will be damaged, and perhaps made useless. Installation and operational mistakes can be costly. > -Would the ROI be higher if I run conventional batteries for the first > two years and wait for the early adopters to drive the price down? Could be. > New technology tends to drop to half price just as soon as the > manufacturing capacity gets up to speed. 20 real amps for a solid > hour might not be so bad at $500. It's a no-brainer at the $200 price > point. > -Can the battery actually deliver its power at that rate without using > a large percentage of its energy to heat its own acid? Yes. You get the same amp-hrs, but not the same watt-hrs. The internal resistance takes some fraction of the voltage delivered and a concomitant portion of the wattage delivered. Unlike your typical lead-acid, however, the amp-hr delivery does not suffer at higher discharge rates. Bill D.