---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 11/07/14: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 0. 12:23 AM - Please Make a Contribution to Support Your Lists... (Matt Dralle) 1. 11:18 PM - Re: lithium facts (Jim Kale) ________________________________ Message 0 _____________________________________ Time: 12:23:13 AM PST US From: Matt Dralle Subject: AeroElectric-List: Please Make a Contribution to Support Your Lists... Dear Listers, Just a reminder that November is the Annual List Fund Raiser. Please make a Contribution today to support the continued operation and upgrade of these great List services!! Pick up a really nice free gift with your qualifying Contribution too! The Contribution Site is fast and easy: http://www.matronics.com/contribution or by dropping a personal check in the mail to: Matt Dralle / Matronics 581 Jeannie Way Livermore CA 94551-0347 Thank you! Matt Dralle Matronics Email List Administrator ________________________________ Message 1 _____________________________________ Time: 11:18:08 PM PST US From: "Jim Kale" Subject: RE: AeroElectric-List: lithium facts I have been studying lithium batteries for several years, when and where I can find information. I am not a chemist, or electrical battery engineer. Just a guy who uses lots of lithium batteries. I use them to power large radio control models aircraft. Common RC models these days use batteries similar to the type you would use in a homebuilt airplane. The RC models I fly typically use 4 cell, 14.4 nominal volt batteries. They are discharged at the rate of about 30 to 150 amps and get totally drained in about 10 minutes. Us modelers have also found that stopping the discharge at about 20 to 30 percent capacity remaining helps keep the cells cool and increases their life substantially. I have seen some lithium batteries catch fire in flight and the RC model (normally fairly expensive - a few hundred dollars and normally built from wood or plastic) goes down in flames. All of the multi cell lithium batteries I use are charged with each cell in the battery pack getting charged individually from a very special charger normally called a balancing charger. That means if you have 4 cells, there are 5 wires coming from a balancing charger that independently charges and monitors each cell while it is charging. I believe that some of the high end lithium batteries in use today have some balancing technology built into each cell and these special batteries may be charged form a common source like an alternator, with a single total charge voltage, sort of like the lead acid battery charging we are all familiar with . Inside each cell or these special lithium batteries, the automatic circuitry keeps each individual cell at a controlled charge current and the proper float voltage when the cell is topped off at the proper voltage for the chemistry being used. All of this automatic control inside each cell, just means there are many potential failure points. If any individual cell, or its automatic charge circuitry goes bad, the whole battery may fail in a mild manor (just quits working) or catastrophic manor (fire). All of this automatic cell monitoring is very expensive. Failures may be dangerous, or just very expensive. The bottom line is if you want to switch to lithium batteries, you should have your charge system designed by some highly qualified folks. Just buying and installing a lithium battery can be very expensive at best, or very dangerous at worst. Let the home builder beware. You can bet Boeing spent some very large sums of money for that lithium battery that caught fire in their 787 Dreamliner. Catastrophic failure is always possible no matter how much you spend for hardware. I work as a flight training systems instructor for a USAF squadron that flies helicopters. For the past 50 years or so, the military forces used Nickel Cadmium batteries in their aircraft. These batteries costs about 8 times as much as lead acid batteries, and required many man hours of service and tests every 4 months. Recently we switched to sealed lead acid batteries (Gel Cells). Now we pay about 5 times less than the NICADs costs, and they don't need any regular maintenance. We just use them till they don't come up to standards, and replace them. Much like you maintain your car. A giant leap backwards, and we save lots of money and get better reliability and performance, not to mention improved safety (those NICADs had a tendency to melt down every now and then.) It doesn't get much better than that. Of course, the quality and performance of sealed lead acid batteries has improved by leaps and bounds over the last 50 years. Jim Kale -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jan de Jong Sent: Thursday, November 6, 2014 5:28 AM Subject: Re: AeroElectric-List: lithium facts --> On 11/5/2014 9:22 PM, Robert L. Nuckolls, III wrote: > > > At 12:46 2014-11-05, you wrote: >> >> >> Well, all I can say - I'm amazed. >> I wonder why I never read anything anywhere but 3.6V to 3.7V - with >> dire warnings about exceeding much... >> >> By the way, these people show 90% charge at 3.6V (100% at 4.2V): >> http://www.powerstream.com/LLLF.htm > > Check out this page . . . > > http://tinyurl.com/2349lq2 > > and the links cited thereon. Isidor Buchmann is > about as knowledgeable as they come about batteries > exceeded only by his generosity for sharing what > he knows. > > > Bob . . . > Interesting. It remains difficult to know when generic "Li-ion" data applies and when specific data is needed for one of the cathode chemistries: "LCO", "LMO", "LFP", "NMC", "NCA", "LTO" see http://batteryuniversity.com/learn/article/types_of_lithium_ion http://batteryuniversity.com/learn/article/lithium_based_batteries What I am guessing at the moment: - the aging mechanisms and lifetime statistics are similar but some are more robust than others - the maximum cell voltage (4.2V) applies to all - charging method and charging phases are similar but they have different capacity vs. final charging voltage curves charging LFP beyond 3.6V doesn't add much, charging LCO beyond 3.8V to 4.2V adds most of the charge see http://www.powerstream.com/lithuim-ion-charge-voltage.htm (the average force required to get an ion into a crystal location is different) - they have different (slow) discharge voltage curves (LFP flat at about 3.2V, LCO steadily decreasing from 3.9V) I could be wrong. Jan de Jong ------------------------------------------------------------------------------------- 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.