---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 01/23/15: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:43 AM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 05:43:30 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Power Generation without Battery? At 14:00 2015-01-21, you wrote: Bob, I think the most likely battery failure modes would be temperature related due mild overcharging/cell imbalance/high ambient temperatures. I think I'll be pretty protected from a runaway thermal overload due to frank over voltage as I will use your Z figures with overload protection/notification. An internal short may also be more likely with lithium than with lead acid. I think you're over-worrying the design decisions before you. Keep in mind that the aviation industry has a rich history of what works and lessons learned for what doesn't. If you sort through the NTSB accident reports, you will be hard pressed to find one that has root cause in failure of an electrical system component to perform as advertised. Even when such stories are found, we read about accidents that just didn't need to happen based on poor architecture, craftsmanship and/or operational decisions . . . NOT borne out of any failure-to-perform to specifications. http://tinyurl.com/mwo3f4x http://tinyurl.com/kv7eugm http://tinyurl.com/msfmldj A well maintained battery (meaning you don't simply run it until it doesn't crank the engine any more) is the single most reliable power source on the airplane. LIMITED in amount of energy stored but a reliable resource when that energy is skillfully managed. Risk of shorted cells in a well managed SVLA based system is essentially zero. Even the lithium incident recently discussed had root cause in severe over-charging from a condition that went unnoticed by the pilot for a LONG period of time. Regarding alternator #2: I request your advice. Running the engine with the EFII requires 10 amps - mostly for electric fuel pump. Are these published, MEASURED numbers? That's a LOT of power for a task that takes less than 5A in my 1987 pickup. Are there examples of your proposed system flying? Have any of those operators shared any current draw observations? I think I need perhaps 15 amps for a comfort margin and to run the radio. Output curve vs rpm is significant considering fuel and ignition function are at stake. But this is a vfr aircraft and I can navigate and fly with nothing but the engine running. So the SD8 does not have adequate output. The SD-8 is a 10A max machine but it does have adequate power for the majority of elegantly crafted architectures Perhaps adapting one of B&C's larger units intended for Continentals? Wind my own? Hopefully something off the shelf though! Wind one? If the over-riding concern driving this thread is system reliability for an airplane that clearly isn't going to spend hours at rarified heights . . . any performance advantages for 'going hi-tech' are not going to be realized. The most proven recipes for success in system reliability used independent ignitions either self-contained (magnetos, p-mags) or very low current demand (light speed, et. als.) Electronic fuel injection for a back-country, puddle jumping pick-em-up truck only adds complexity with limited return on investment. If it were my airplane: Lyc with p-mags or light speed ignition, L-40 belt driven alternator, SD-8 pad driven alternator, well maintained SLVA battery (or EarthX if you're ready to $spend$ just for weight reduction.) This combination has evolved with a track record of ancestral architectures going back 100 years. Clearly, your project has the potential for being a great fun-machine. But time, talent and resources being contemplated to make it look more like a Lancair IVP only drives up complexity, adds to your burdens for understanding all the nuances of its architecture, drives up worry-pressures and adds almost nothing to observable performance. I contacted B&C on the self/persistent excitation issue and was advised that the SD8 requires a battery in the system to operate the regulator. He referred me to you. Also called Plane Power as it seemed their internally regulated design should be able to continue to run following removal of external battery power, but was advised not. Answers may have been tainted by my emphasis about actually keep the engine running! Actually, self-excitation on the SD-8 was discussed here on the List some time back. Figure Z21 in the 'Connection illustrates the concept for adding a few components to keep PM alternator's rectifier/regulators 'awake' sans battery. I don't think I have any large loads in the plane which would tend to stun the self-excited alternator. Think I may make a small placard to remind about being gentle with manipulations if running under such circumstances. I believe you drew Z12 and Z13 prior to predominance of 100% electrically dependent engines. They both show a magneto in the system for example. Do you feel these Z figures are appropriate for adapting to electrically dependent engines using a lead acid battery? Do you think Z12/13 are reasonable for use with a current technology (eg EarthX) Li battery? Which Z do you favor and why? If yes, is there some means to enhance the alternators propensity to continue to produce power following battery failure? If you spend as much time taking care of a battery as you do worrying about it failing, then it's not going to fail. Taking care of it means, "operate it within well established limits and preventative maintenance to verify integrity." What do you recommend for a first and second alternator for my system? Minimum output needed is 15 amps at perhaps 1800 engine rpm. Weight is a factor for my setup. Z-13/8, simple ignition/fuel delivery, battery optional but DEMANDING of your attention no matter what alternators or battery is installed. We tend to worry more about changing oil in the engine or watching tire tread wear than to track and verify battery performance. Yet more unhappy days in the cockpit are rooted in poorly archtiectured/ maintained electrical systems than for dirty oil or worn tires. 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.