---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 03/20/14: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:21 AM - Re: EarthX lithium (Stuart Hutchison) 2. 11:57 AM - Re: EarthX lithium (Robert L. Nuckolls, III) 3. 12:14 PM - Re: Re: New Over-Voltage Protection Architecture (Robert L. Nuckolls, III) 4. 05:23 PM - Re: EarthX Batteries (speedy11@aol.com) ________________________________ Message 1 _____________________________________ Time: 12:21:19 AM PST US From: Stuart Hutchison Subject: RE: AeroElectric-List: EarthX lithium G'day Bob N. Your comments in the PDF file about battery Ah rating under different operating conditions reminded me of an interesting annecdote. About 10 years ago, Energiser began marketing a series of cheap (approx $20) AA battery powered chargers for cell phones. They are a simple plastic case (inc circuit) for two primary AA cells, plus a short adaptor cord option for the various cell phone models. Turns out they come fitted with lithium cells for good reason. >From spec data sheets at the time, the rating for a standard Energiser alkaline AA cell was typically around 2700 mAh. The lithium cells were about 3200 mAh, yet manufacturers quoted 5 to 7 times the endurance for lithium cells in high power devices. This seemed counter-intuitive given a similar mAh rating. In practice, the lithium cells can deliver higher current without the internal resistance soaring through the roof, so most of their energy is delivered to the load rather than wasted as heat. It was easily proven by replacing the AA lithium cells with alkaline cells. The alkaline cells became too hot to touch and delivered about half a cell phone charge, while the lithium cells delivered about 2.5 full charges. Conversely, using lithium cells in a low power device such as a wall clock would offer a very poor return on investment, given the lithium AA cells cost about 4 times the price. Cheers, Stu -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Tuesday, March 18, 2014 3:41 AM Subject: AeroElectric-List: EarthX lithium I just became aware of EarthX batteries based on comments here on the list. I visited their website and studied a variety of assertions and comparisons designed to promote sales. At first blush, these folks are hanging their marketing hats on the same philosophy as other suppliers of lithium technologies. See attached document . . . The DEARTH of good engineering data for these products makes it difficult if not impossible to craft a well considered integration of the current COTS (commericial off the shelf) offerings onto airplanes. I had to delay submission of the last of four Kitplanes articles for a month . . . not because theres a paucity of choices . . . but because the folks selling them can't define performance in rational numbers. Still digging . . .. Bob . . . ________________________________ Message 2 _____________________________________ Time: 11:57:00 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: EarthX lithium > . . . using lithium cells in a low power device such as a wall > clock would offer a very >poor return on investment, given the lithium AA cells cost about 4 times the >price. Yeah, your talking about these critters . . . Emacs! They're in the Size 91 package (AA) but offer a lithium-Iron couple that's in the same ballpark as the carbon-zinc and zinc-manganese flashlight cells (1.5 volts). If you compare E91 alkaline cell data Vhttp://tinyurl.com/nt2x8hd with the L91 lithium-iron data http://tinyurl.com/otkeubs We see that both products are in the same ballpark for contained energy but the L91 cell internal resistance is about 1/2 that of the E91. So not only do you get slightly more total energy, your access to that energy at high discharge rates suffers about 1/2 the losses in heat. This 'lithium' product is a different animal from the devices we're pondering as replacement for engine-cranking/standby service. The boss-hogg lithium cells are 3.3V couples and generally much lower resistance still . . . It's unfortunate that characteristic performance of two cells are not presented in the same pews . . . suffice it to say that the approx 1/2 internal resistance will toss off less energy under high demand loads. On the Nickle-Metal Hydride side of the house one may acquire 1.2V chemistry with very attractive internal impedances . . . http://tinyurl.com/nj5xx85 At 1.2V vs. 1.5 volts the contained energy in watt-seconds suffers slightly but they'll readily deliver their contents at high rates. Down-side is that the self-discharge characteristics of Ni-Mh compared to the Lithium-Iron or Zinc-Manganese cells is pretty sad. Up-side is that you can readily re-use these cells many times over and their acquisition costs are nominal. http://tinyurl.com/nklo97k Your right, lithium-iron AA cells poor value compared to other choices . . . unless your design goals absolutely demand high rate discharge support AND long shelf life. Its all in the design goals . . . Bob . . . ________________________________ Message 3 _____________________________________ Time: 12:14:10 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: New Over-Voltage Protection Architecture At 10:58 AM 3/19/2014, you wrote: >You might be approaching a situation where "the cure is worse than >the disease". You have to be careful when stacking widgets on top >of gizmos in pursuit of greater reliability. That approach quite >often leads to greater complexity & lower reliability. Good put. What is the line of thought that drives the notion that simple removal of field voltage from a runaway system is inconsistent with our assessment of risk? I'll have to ask around . . . I've been disconnected from the field service loop in regulators for some years . . . but I don't recall any controllers ever coming back to B&C where a regulator fallen from grace was blessed with salvation by the ov protection system. I'm not suggesting that such failure rates are zero but they ARE quite small. Further the prudent response to a competent FMEA dictates that we include such protection in spite of those low failure rates. It's been a long time since I've observed a car approaching me at night with lights that were too blue/bright demonstrating the fact that a poor battery was doing its best to stand off a runaway alternator. I'm also reading anecdotal bits about stock, automotive alternators being incorporated onto aircraft sans ov protection. It MIGHT be that contemporary regulators have achieved 10 to the minus 9 or better failure rates that suggest the ov protection is no longer necessary/useful. If anyone runs across such an incident, I'd like to hear about it. Bob . . . ________________________________ Message 4 _____________________________________ Time: 05:23:10 PM PST US Subject: AeroElectric-List: Re: EarthX Batteries From: speedy11@aol.com I concur with Bob's comments. My dealings with the folks at EarthX has be en professional and forthcoming. It appears they are pushing hard to become the market leaders and their bat tery monitoring system may be just the thing to get them there. I have decided to distribute their batteries at my FBO operation and I will be ordering two batteries soon to replace the PC680s in my RV-8A (Reno Rac e 84). I will follow up with non-technical, but nonetheless interesting da ta points on my experience using the lithium batteries. Stan Sutterfield Spruce Creek FBO Daytona Beach A heads-up to the List on my conversations with EarthX. Of ALL the lithium wannabes I've approached for expanded data on the operation and performance of their batteries, EarthX has been the ONLY one to respond in any positive and professional manner. The e-mails I've forwarded to the List are conversations with an individual in sales. I've received a data dump from an applications person who promises to draw design and performance talents into the conversation. I'm not going to forward any more emails to the List out of respect for their willingness to share what may be considered proprietary data. But I want to make the List aware of the fact that EarthX seems interested in widening their customer base on a foundation of well considered application of their products. I'm going to offer them assistance in crafting functional specifications that speak purely to performance in terms that would be appreciated by my colleagues in TC aviation. At the same time, I will acquire foundation for offering solid advice to the OBAM aviation community as to suitability to task for EarthX . . . or any other lithium offering. Watch this space. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.