---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 01/25/15: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:59 AM - Dual Alternator, Dual Battery, Single Bus (Dan Brown) 2. 09:45 AM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III) 3. 12:42 PM - Re: Dual Alternator, Dual Battery, Single Bus (Robert L. Nuckolls, III) 4. 01:31 PM - Re: Power Generation without Battery? (user9253) 5. 03:13 PM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III) 6. 03:23 PM - ASTM membership is now active . . . (Robert L. Nuckolls, III) 7. 04:18 PM - Re: Power Generation without Battery? (user9253) 8. 04:43 PM - Re: Power Generation without Battery? (user9253) 9. 05:18 PM - FMEA (user9253) 10. 06:18 PM - Re: Re: Power Generation without Battery? (Robert L. Nuckolls, III) 11. 06:44 PM - Re: Power Generation without Battery? (user9253) 12. 07:07 PM - Re: Re: Power Generation without Battery? (Robert Borger) ________________________________ Message 1 _____________________________________ Time: 07:59:37 AM PST US From: "Dan Brown" Subject: AeroElectric-List: Dual Alternator, Dual Battery, Single Bus Hello Bob, My project will have a dual electronic ignition and an all-electric panel. I intend to have the two battery and individual battery buses per your Figure Z-30. I will have a single power bus that is supplied by a 60 amp main alternator (Plane Power AL12-C60) with a 30 amp backup alternator (Plane Power FS1-14). The B-leads from both alternators are connected through a Maxi fuse block to the hot side of the starter contactor which then goes through the firewall to the bus. I have some questions: 1) The 6 AGW B-leads from the alternators can easily carry 80 amps. Can I protect the both leads with 80 amp Maxi fuses? I believe I might have read that this is okay in the List FAQs. 2) According to Hartzell Engine Technologies (new owners of Plane Power alternators) the main alternator puts out 14.2 v and the backup puts out 13.6 v so if the main drops below 13.6 v the backup takes over. Their wiring diagram does not show a diode in the circuit to stop the flow of electricity from the bus to the B-terminal of the backup alternator. I thought that this may affect the backup alternators life but the technician at HET said not to worry about it. If I was really concerned I could turn the field off on the backup under normal operation and turn it on in the event of a low voltage indication. I prefer the automatic takeover of the backup so my question is this, do I need to have a diode in the circuit to block the reverse flow to the backup alternator or is the 0.6 v potential no big deal? If it is prudent to add the diode what type of diode do you recommend? 3) I also think I remember reading in the List FAQs (but can't seem to find it) that in the event of the battery contactor opening and disconnecting the battery from the bus, a load on the bus could cause precipitous failure of the alternator. It would be nice to have a battery contactor open indicator light. What is the best way to add such a device to your dual battery circuit? Thanks, Dan ________________________________ Message 2 _____________________________________ Time: 09:45:19 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Power Generation without Battery? At 09:11 2015-01-24, you wrote: > >Lightspeed and others recommend connecting electronic ignition >directly to the battery. . . . a sentiment that has been echoed in the AEC publications for a long time. Fuel pumps too . . . any component which depends on DC to keep the engine running . . . > Since Lithium batteries have been known to short out, maybe they > should not be used. SLVA batteries never short? > If the battery shorts out, so will the alternators be shorted. . . . okay, step through the FMEA for a shorted cell in any battery. How will the event manifest? How will the pilot become aware of it? What is the recommended plan of action to be taken by the pilot? Most important . . . what features can be incorporated into the full-up system to offer a pilot the best response to the event? > Another failure mode to be considered is a failed master > contactor shortly after takeoff. Again, step through the FEMA . . . > That is not very likely to happen, but it could. Regardless of > what the manufacturers say, an alternator could keep supplying > power to the aircraft electrical system. Yes . . . consider the plots of data I took on an exemplar SD-8 at B&C about 20 years ago http://tinyurl.com/n5yd3vw In particular, page 9 of the document that cites 14.5v output at 9.7 amps with a 10KuF 'smoothing' capacitor and NO BATTERY. One a quality we've not discussed here is the value of the legacy 'smoothing' capacitor might add in improving NO BATTERY performance of the rectifier-regulator. A question I will explore in the future. > Thus the pilot would not know that the master contactor has > opened. If the duration of the flight is longer than the energy > stored in the battery (likely with a Li battery), then the engine > will quit. A solution to the failed master contactor scenario is a > relay in parallel (disabled during engine cranking). That's one solution . . . are there others? > Even if these failure modes are unlikely, everything needs to be > considered when designing an electrical system. Accidents happen > sometimes due to unlikely and unexpected chain of events. . . . but with some tempering based on lessons learned and probabilities based on history. Yeah, on occasion some airplanes throw a prop . . . bad bolts? Probably not. Bad installation of bolts? Probably. Broken crankshaft . . . that's a stretch. But again, history has demonstrated the MAJOR cause of uncomfortable termination of flight is inattention to simple-ideas with performance histories rich in data. Bob . . . ________________________________ Message 3 _____________________________________ Time: 12:42:02 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Dual Alternator, Dual Battery, Single Bus At 09:58 2015-01-25, you wrote: >Hello Bob, >My project will have a dual electronic ignition and an all-electric >panel. I intend to have the two battery and individual battery buses >per your Figure Z-30. I will have a single power bus that is >supplied by a 60 amp main alternator (Plane Power AL12-C60) with a >30 amp backup alternator (Plane Power FS1-14). The B-leads from both >alternators are connected through a Maxi fuse block to the hot side >of the starter contactor which then goes through the firewall to the bus. >I have some questions: >1) The 6 AGW B-leads from the alternators can easily carry 80 >amps. Can I protect the both leads with 80 amp Maxi fuses? I believe >I might have read that this is okay in the List FAQs. Yes . . . as long as your bus feeder protection is much more robust than the downstream protection . . . you can choose about anything. Consider the chain of protection for some device you might plug in the wall . . . Protection within the device needs to be much faster than the breaker that feeds that outlet considering that it too may be loaded to the maximum continuous rating of the device. In other words, the failure inside the appliance needs to have a small fraction of total effects on the breaker in the panel. As you move upstream in the distribution system, each branch is protected with careful attention to dynamics such that a small event in somebody's house doesn't trigger a 'blackout' in the neighborhood. It might be better to use the miniature current limiters like . . . http://tinyurl.com/qj4vojb In holders with vertical studs upon which you stack the current limiter tabs and any/all ring terminals with good force. >2) According to Hartzell Engine Technologies (new owners of >Plane Power alternators) the main alternator puts out 14.2 v and the >backup puts out 13.6 v so if the main drops below 13.6 v the backup takes over. Yes . . . B&C pioneered that philosophy 20+ years ago when we introduced the first pad-driven, wound- field alternators into OBAM aviation. > Their wiring diagram does not show a diode in the circuit to > stop the flow of electricity from the bus to the B-terminal of the > backup alternator. I Doesn't need it. Alternators, unlike generators, are incapable of taking power INTO their b-terminal. They have diodes built in. See: http://tinyurl.com/okegwfd > thought that this may affect the backup alternators life but the > technician at HET said not to worry about it. . . . now, if he had only explained why you wouldn't have been left with a dangling question . . . >If I was really concerned I could turn the field off on the backup >under normal operation and turn it on in the event of a low voltage >indication. I prefer the automatic takeover of the backup so my >question is this, do I need to have a diode in the circuit to block >the reverse flow to the backup alternator or is the 0.6 v potential >no big deal? If it is prudent to add the diode what type of diode do >you recommend? Absolutely not. Wire with guidance from Figure Z-12 which describes the ancestral configuration . . . http://tinyurl.com/ag46m2f >3) I also think I remember reading in the List FAQs (but can't >seem to find it) that in the event of the battery contactor opening >and disconnecting the battery from the bus, a load on the bus could >cause precipitous failure of the alternator. It would be nice to >have a battery contactor open indicator light. What is the best way >to add such a device to your dual battery circuit? As long as you don't have 250w incanescant landing lights or an electro-hydraulic pump system, transient loads capable of stalling a self-excited alternator don't exist. Further, since you're running dual batteries, you'd have to crap two contactors to set that scenario up. What does your power distribution look like. What electro-whizzies from which which busses? Bob . . . ________________________________ Message 4 _____________________________________ Time: 01:31:16 PM PST US Subject: AeroElectric-List: Re: Power Generation without Battery? From: "user9253" > I'd like to monitor battery temp using a probe and my on board electronics, and to have some way to electrically isolate or even physically remove the battery Here a links to thermocouples. Most EMS or EFIS have inputs for type J. http://www.omega.com/pptst/WT.html http://www.omega.com/pptst/SA2.html If the EFIS alarms with temperature rise, the master switch can be shut off. > So I am concerned about the Li battery being a single point of failure capable of stopping the engine. > How can I design around this problem? Are there any permanent magnet alternators (dynamo) available for your engine? One possibility (and I am not necessarily recommending this) is to dedicate a dynamo to supply electrical power to only one fuel pump and one ignition, keeping this circuit completely isolated and independent of the rest of the aircraft electrical system (except for common ground). Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437626#437626 ________________________________ Message 5 _____________________________________ Time: 03:13:44 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Power Generation without Battery? At 15:30 2015-01-25, you wrote: > I'd like to monitor battery temp using a probe and my on board electronics, and to have some way to electrically isolate or even physically remove the battery Here a links to thermocouples. Most EMS or EFIS have inputs for type J. http://www.omega.com/pptst/WT.html http://www.omega.com/pptst/SA2.html If the EFIS alarms with temperature rise, the master switch can be shut off. But where do you put a thermocouple? In a 4x4 array of cells, there are 16 potential failures. How can you be certain that monitoring any particular location outside the battery will offer timely notification of a failure on any of the 16 cells inside? What constitutes an alarming temperature rise? Once that condition is noted, what value is there in any pilot action. Shut off the battery? Jettison the battery? > So I am concerned about the Li battery being a single point of failure capable of stopping the engine. > How can I design around this problem? Design a system that doesn't set batteries on fire (timely notification of or reaction to over voltage) and perhaps incorporate batteries with full-up Battery Management Systems that will function to PREVENT such events as opposed to reacting to the event AFTER it occurs. Are there any permanent magnet alternators (dynamo) available for your engine? One possibility (and I am not necessarily recommending this) is to dedicate a dynamo to supply electrical power to only one fuel pump and one ignition, keeping this circuit completely isolated and independent of the rest of the aircraft electrical system (except for common ground). Please make the argument for the battery (of any chemistry) NOT being the most reliable source of energy on the airplane. We've read narratives for all manner of puffed-up and/or vented-dry SVLA batteries . . . some of which have indeed experienced internal fires. ALL such cases were preceded by a sustained ov even that went unnoticed. Batteries don't instantly go POOF when the alternator runs away. To this date, are we aware of ANY battery in distress that was NOT triggered by an event borne of poor system architecture or operator inattention? Bob . . . ________________________________ Message 6 _____________________________________ Time: 03:23:23 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: ASTM membership is now active . . . Just finished the keystrokes needed to join ASTM. I downloaded a constellation of specs relevant to the LSA market. Got some reading to do . . . Bob . . . ________________________________ Message 7 _____________________________________ Time: 04:18:14 PM PST US Subject: AeroElectric-List: Re: Power Generation without Battery? From: "user9253" Chris, My mistake, I should have read your first post more closely. You do intend to use the SD-8 dynamo. The Rotax 912i fuel injected engine has two dynamos, one for the engine and one for the rest of the aircraft. The ignition and fuel pumps can also be powered by the other dynamo if necessary. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437632#437632 ________________________________ Message 8 _____________________________________ Time: 04:43:03 PM PST US Subject: AeroElectric-List: Re: Power Generation without Battery? From: "user9253" > Please make the argument for the battery (of any chemistry) NOT being the most reliable source of energy on the airplane. I agree that SVLA are very reliable. I am not very knowledgeable about the Lithium batteries except for the news reports which sensationalize the fire without explaining why it happened. If you think that the Lithium batteries are safe (if properly charged and discharged) for use in aircraft, then that is good enough for me. But I will wait until the price comes down to the level of lead acid batteries before buying a Lithium. In the mean time, I will keep my plane light weight by watching what I eat. :-) Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437633#437633 ________________________________ Message 9 _____________________________________ Time: 05:18:33 PM PST US Subject: AeroElectric-List: FMEA From: "user9253" > . . . okay, step through the FMEA for a shorted cell in > any battery. How will the event manifest? How will the > pilot become aware of it? What is the recommended plan > of action to be taken by the pilot? Most important . . . > what features can be incorporated into the full-up system > to offer a pilot the best response to the event? Good suggestion and worthy of a new thread. A shorted AGM battery is highly unlikely. But I think the symptoms would be low system voltage and high current on the ammeter no matter if the shunt measures battery current or alternator output. Of course the pilot would not know what the problem is. There could be a short external to the battery (which is more likely). The prudent thing to do would be to shut off the master switch and land to investigate the problem. Another interesting failure is of the master contactor coil. How will the pilot know? If the alternator keeps working, which is likely, then there might not be any clues. The voltage will remain the same. An alternator load meter will not change much. An ammeter that measures battery charge-discharge current will be on zero, not far from where it usually is. The pilot might not realize the contactor coil failed until he closes the throttle or maybe not until the next engine start. It would be worthwhile to analyze each component of the electrical system and ask, if this part fails, how will I know and what should I do about it. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437636#437636 ________________________________ Message 10 ____________________________________ Time: 06:18:30 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Power Generation without Battery? At 18:16 2015-01-25, you wrote: > >Chris, >My mistake, I should have read your first post more closely. You do >intend to use the SD-8 dynamo. > The Rotax 912i fuel injected engine has two dynamos, one for the > engine and one for the rest of the aircraft. The ignition and fuel > pumps can also be powered by the other dynamo if necessary. The last time I dug through the MM on a 912, a constellation of windings on the PM alternator stator core were defined as follows: Emacs! 4 each, trigger coils for spark timing of the 8 plugs in pairs (waste spark). These will be a low voltage, low energy signal to the ignition modules. 2 each, capacitor charging coils, one for each module. These are moderate energy, high voltage windings that charge a capacitor with each pass of the magnet. This few hundred volts of capacitor charge is stepped up in coils to the killovolt levels needed for plugs. 1 each, tachometer signal coil. Another low voltage, low energy signal generator for an electronic tach. 1 each, PM alternator coil. High energy, high current in the 250W class. This is the only winding available to drive any sort of rectifier-regulator to operate ship's electro-whizzies. All other windings are separate and dedicated to their respective tasks thus making ignition systems completely independent of the power generation system. Some Rotax installations include aa SECOND, optional belt driven alternator in the 40-55A class. This second alternator has been teamed with the integral PM alternator in a Figure Z-13/8 configuration on several OBAM aircraft . . . I've seen some pad driven alternators on Rotax engines . . . in the spot for vacuum pumps. But this pad is slow and I don't think THAT particular #2 alternator was very practical. In any case, only one coil of eight on the back of a Rotax 912/914 generates power for ship's electrical needs. Bob . . . ________________________________ Message 11 ____________________________________ Time: 06:44:25 PM PST US Subject: AeroElectric-List: Re: Power Generation without Battery? From: "user9253" The Rotax fuel injected engine is new, only having been for sale for the last year or two. It is an electrically dependent engine, not only for the ignition, but also for the high pressure fuel pumps. Thus, the electrical system needs to be fail safe. Below is an excerpt from the installation manual. http://www.flyrotax.com/customer-serviceImpressum/technical-publications.aspx Joe > The internal generator has two isolated coils integrated (individual generators). During the starting operation, the EMS system is powered by the battery. With sufficient speed generator B takes over this function. After the EMS system check, generator A takes over the supply of the EMS system (engine), if the switching threshold is exceeded. Generator B is then used to supply the aircraft instruments and for charging the battery. > Generator A 14.2 V/16 A (220 W nominal capacity at 20C/68 F) > Generator B 14.2 V/30 A (420 W nominal capacity at 20C/68 F) > > If generator A fails, generator B takes over its functions. The onboard computer and the instruments will be supplied by the battery. The battery will no longer be charged! > > If generator B fails, the battery will no longer be charged. The engine still runs on generator A and the instruments will be supplied by the battery. The function of the instruments depends on the state of charge of the battery. > For monitoring the battery voltage and to ensure that the battery is charged, a voltmeter and ammeter is necessary. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437640#437640 ________________________________ Message 12 ____________________________________ Time: 07:07:56 PM PST US From: Robert Borger Subject: Re: AeroElectric-List: Re: Power Generation without Battery? Bob, FWIW, I have one of those (Nippon Denso) alternators on the vacuum pad of my 914. It is actually capable of producing more amps than the ROTAX built-in alternator. But it takes 2500 rpm for it to come online. Best regards, Robert Borger, President Geowhiziks & Doodlebugging, Inc. Certified Petroleum Geophysicist AAPG#101 3705 Lynchburg Dr. Corinth, TX 76208-5331 (C) 817-992-1117 Sent from my iPad > On Jan 25, 2015, at 19:17, Robert L. Nuckolls, III > I've seen some pad driven alternators on > Rotax engines . . . in the spot for > vacuum pumps. But this pad is slow and > I don't think THAT particular #2 alternator > was very practical. ------------------------------------------------------------------------------------- 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.