---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 03/26/14: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:53 AM - The lithium saga slogs onward . . . (Robert L. Nuckolls, III) 2. 07:43 AM - Re: DIY CBOVM: variations on a theme (user9253) 3. 08:25 AM - Re: Re: DIY CBOVM: variations on a theme (Jeff Luckey) 4. 09:02 AM - Continental Motors magneto data (Robert L. Nuckolls, III) 5. 09:45 AM - Re: Re: DIY CBOVM: variations on a theme (K) 6. 09:54 AM - Re: DIY CBOVM: variations on a theme (user9253) 7. 09:55 AM - Re: Re: New Over-Voltage Protection Architecture (Robert L. Nuckolls, III) 8. 10:05 AM - Re: Re: DIY CBOVM: variations on a theme (Robert L. Nuckolls, III) 9. 10:26 AM - Re: DIY CBOVM: variations on a theme (user9253) 10. 10:59 AM - Re: Re: DIY CBOVM: variations on a theme (K) 11. 12:43 PM - The lithium saga slogs onward . . . (Robert L. Nuckolls, III) 12. 12:47 PM - Re: Re: DIY CBOVM: variations on a theme (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:53:17 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: The lithium saga slogs onward . . . In my quest to identify suppliers of lithium batteries who will share operational details of their BMS (battery management system) AND useful contained energy plots, few suppliers have demonstrated an interest in satisfying the unique curiosity of those who build and fly airplanes. So far, EarthX is the only one who has responded positively. I have documentation that describes their BMS operating philosophy. No family of discharge curves yet . . . but them, most of their customers are narrowly focused on engine cranking cupcakes with a frosting of weight reduction. I need to wrap of installment IV of the battery series for Kitplanes . . . as of this moment, I'm still short the necessary information to beat the drums in favor of ANY commercial off the shelf lithium product for OBAM aircraft. My misgivings are NOT rooted in either disappointment for weight savings or ability to get the engine started. The problem is centered on knowing what we don't know . . . exactly what size battery is needed to replace the legacy SVLA products in which we have considerable confidence. Watch this space . . . Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:43:04 AM PST US Subject: AeroElectric-List: Re: DIY CBOVM: variations on a theme From: "user9253" I repeated testing of the over-voltage circuit today, doing a better job of connecting wires. If the voltage is steadily increased, the SCR fires at 16.2 volts. But if the voltage is set at 16.0 volts and held there, the SCR would fire after waiting a couple of minutes. Probing the input with a voltmeter intermittently caused the SCR to fire only when the voltage was above 15.9. Circuit instability, if any, is within 0.1 volt of the set-point. The adjustable voltage power supply only cost $6. Who knows how stable that is. The components are all through-hole, not surface mounted, and are mounted to a 1 x 2 inch area of PCB. I am happy with the circuit. I intend to connect the over-voltage circuit in series with a relay coil that is powered by a 3 amp fuse.. The normally closed contacts of the relay will be in series with the AC output of the permanent magnet dynamo. In case of high voltage, the SCR will fire, connecting one leg of the coil to ground to energize the relay, opening the AC circuit to the rectifier/voltage regulator. The SCR will continue to hold the relay energized until battery power is disconnected from the relay coil. This will not be a crowbar type of over-voltage protection. So no circuit breaker is required. High voltage will not blow the fuse. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=421067#421067 ________________________________ Message 3 _____________________________________ Time: 08:25:02 AM PST US From: Jeff Luckey Subject: Re: AeroElectric-List: Re: DIY CBOVM: variations on a theme Joe,=0A=0A1. How much power can the dynamo produce?- =0A2. Are there only 2 wires for the AC output? (I've never worked w/ a PM type alternator but most non-PM machines have 3 wires for AC output)=0A3. As you probably alrea dy know, on some relays, the current-handling capability of the NC contacts is less than the NO contacts=0A=0A=0A-Jeff=0A=0A=0A=0A____________________ ____________=0A From: user9253 =0ATo: aeroelectric-list@ matronics.com =0ASent: Wednesday, March 26, 2014 7:40 AM=0ASubject: AeroEle ctric-List: Re: DIY CBOVM: variations on a theme=0A =0A=0A--> AeroElectric- List message posted by: "user9253" =0A=0AI repeated test ing of the over-voltage circuit today, doing a better job of connecting wir es.- If the voltage is steadily increased, the SCR fires at 16.2 volts. - But if the voltage is set at 16.0 volts and held there, the SCR would f ire after waiting a couple of minutes.- Probing the input with a voltmete r intermittently caused the SCR to fire only when the voltage was above 15. 9.- Circuit instability, if any, is within 0.1 volt of the set-point.- The adjustable voltage power supply only cost $6.- Who knows how stable t hat is.- The components are all through-hole, not surface mounted, and ar e mounted to a 1 x 2 inch area of PCB.- I am happy with the circuit.=0A - I intend to connect the over-voltage circuit in series with a relay coi l that is powered by a 3 amp fuse..- The normally closed contacts of the relay will be in series with the AC output of the permanent magnet dynamo. - In case of high voltage, the SCR will fire, connecting one leg of the c oil to ground to energize the relay, opening the AC circuit to the rectifie r/voltage regulator.- The SCR will continue to hold the relay energized u ntil battery power is disconnected from the relay coil.=0A- This will not be a crowbar type of over-voltage protection.- So no circuit breaker is required.- High voltage will not blow the fuse.=0AJoe=0A=0A--------=0AJoe Gores=0A=0A=0A=0A=0ARead this topic online here:=0A=0Ahttp://forums.matron ============== ________________________________ Message 4 _____________________________________ Time: 09:02:26 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Continental Motors magneto data Hat tip to Neal George who has provided us with a helpful library of service and training data on Continental's magneto systems. List members are invited to review the documents available at: http://tinyurl.com/llpc5lj . . . and download as their interest and needs dictate. Bob . . . ________________________________ Message 5 _____________________________________ Time: 09:45:28 AM PST US From: K Subject: Re: AeroElectric-List: Re: DIY CBOVM: variations on a theme In regards to stability you might check that there is a capacitor across the voltage reference diode and another from the SCR gate to ground. If you happen to have an old circuit diagram dated before about 2005 it may not show that update. One nice thing about the crowbar and circuit breaker in the Z diagrams is that the voltage is brought under control immediately when the SCR fires. If I understand your post it sounds like your implementation waits for the relay to open and for any subsequent arcing to extinguish. Perhaps that is good enough but it seems preferable to use the circuit breaker as per the Z diagrams so that the SCR clamps the voltage faster. Might be other small advantages as well such as a subsequent dead battery could not cause the alternator to come back on line. Ken On 26/03/2014 10:40 AM, user9253 wrote: > > > I repeated testing of the over-voltage circuit today, doing a better > job of connecting wires. If the voltage is steadily increased, the > SCR fires at 16.2 volts. But if the voltage is set at 16.0 volts and > held there, the SCR would fire after waiting a couple of minutes. > Probing the input with a voltmeter intermittently caused the SCR to > fire only when the voltage was above 15.9. Circuit instability, if > any, is within 0.1 volt of the set-point. The adjustable voltage > power supply only cost $6. Who knows how stable that is. The > components are all through-hole, not surface mounted, and are mounted > to a 1 x 2 inch area of PCB. I am happy with the circuit. I intend > to connect the over-voltage circuit in series with a relay coil that > is powered by a 3 amp fuse.. The normally closed contacts of the > relay will be in series with the AC output of the permanent magnet > dynamo. In case of high voltage, the SCR will fire, connecting one > leg of the coil to ground to energize the relay, opening the AC > circuit to the rectifier/voltage regulator. The SCR will continue to > hold the relay energized until battery power is disconnected from the > relay coil. This will not be a crowbar type of over-voltage > protection. So no circuit breaker is required. High voltage will > not blow the fuse. Joe > > -------- Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=421067#421067 > > ________________________________ Message 6 _____________________________________ Time: 09:54:44 AM PST US Subject: AeroElectric-List: Re: DIY CBOVM: variations on a theme From: "user9253" Jeff, 1. The Rotax 912 dynamo can generate up to about 20 amps. Although many recommend not loading it to more than 16 amps. My plane uses about 10 amps. 2. Yes, the AC output has two wires and is single phase. 3. If I am interpreting this data sheet correctly http://pewa.panasonic.com/assets/pcsd/catalog/cb-catalog.pdf the normally closed contacts can handle 30 amps. I suspect that, over the long term, corrosion due to lack of exercise will be more of a problem than the contact rating. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=421074#421074 ________________________________ Message 7 _____________________________________ Time: 09:55:49 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: New Over-Voltage Protection Architecture >Hmm, the link works for me. >http://www.vansairforce.com/community/showthread.php?t=111102 >All 12 posting in this thread are from the last 2 or 3 days. Yeah, had a momentary short between the heaphones. Let's parse the narrative . . . Last Wednesday I flew from Melbourne to Hobart in my RV-7 (about an hour of the 2.5hr flight is over water - Bass Strait). Faultless day, faultless flight. Yesterday I jumped in my RV and flew from Hobart to Bruny Island (short flight - no problems). When I departed Bruny Island I got a Low Voltage Warning on my EFIS a couple of minutes after take off. I have an EXP2 Buss DC Load Center with indicator panel and GRT EFIS. EXP2 Indicator panel showed that the Alternator had switched off and the GRT was showing 13.3Volts and dropping. "Dropping" is not very quantified but the initial bus voltage excursion will be rather steep. A battery charges a 14.5 and discharges at 12.5 . . . so the first few seconds, probably less than a minute will show a steep drop of more than a volt. [] Note that this exemplar battery loaded to 1C starts 'working' at just over 12 volts. If he had been fitted with a flight worthy, 17 Ah battery and could reduce his loads to say 4A (.2C) his trip home would have been uneventful . . . I know you shouldn't turn the alternator off when the engine is running however I cycled the Alt Switch to see if i could get it to reset but no change resulted. There is no rational prohibition for turning the alternator on/off while the engine is running . . . particularly if there's a flight worthy battery in service. At this point I was over water so I requested a direct track to Hobart and landed to check it out (while I still had some volts). By the time I landed I didn't have enough volts to start the engine. I recharged the battery overnight. This morning I started the engine and the Alternator came back on line and operated as normal. After warm ups I obtained a clearance and departed Hobart....3 mins later the Alternator failed again and I returned to Hobart. What's wrong with this story? After the FIRST failure of the alternator, the battery was incapable of supporting sustained flight for more than a few minutes. Before I shut down I momentarily switched the master switch off and then immediately back on - this recycled the alternator and it was operating normally again. I suspected it may have been an over voltage condition because the EXP2 Buss has over-volt protection which turns off the Alternator and you have to remove battery power to reset it. I did a ground run for approximately 3 minutes at 2200rpm but it continued to operate normally (i thought this might cause it to fail). I shut down and removed the cowls and checked the belt and checked the connectors. Removed and refitted the connector on the back of the Alternator - all seemed fine. Following this I replaced the cowls and then inspected the EXP2 Buss to see if there were any loose connections. All seemed OK. I started the engine again and Alternator was operating normally after run-ups and a higher rpm check. I taxied out to the runway and I watched the indicator panel on departure...shortly after take off (before I had reduced the rpm) the indicator panel showed a high voltage warning which then reverted to a low voltage warning probably due to over volt protection kicking in. I completed the circuit and landed, tied down my RV and came to the conclusion that I wasn't going to fly back over Bass Strait in a hurry so I jumped on a commercial flight home. The peek-n-poke is a good and necessary part of the troubleshooting activity. His decision to use alternate transportation was prudent. We've discussed system reliability philosophies here on the list for many years. Crafting design goals should be followed with design, testing and maintenance to those goals. If this gentleman had crafted a plan-b with capable and confident endurance (can anybody say Z-13/8?) it's unlikely that this story would have been written. Yes, things break on airplanes. The real story here is not the difficulty with his alternator or it's associated controls. It's about his ABSOLUTE DEPENDENCE on the alternator for comfortable transition over deep water. So now the dilemma - I didn't bring the Alternator home with me so I can't bench test it. My thoughts are to purchase a replacement alternator and take it to Hobart and fit it to see if the problem goes away. If not, then I will have a spare alternator and the problem is more likely to be a fault in the over volt protection on the EXP2 Buss. Has anyone had a similar experience with the Vans 60amp Alternator and EXP2 Buss combination? If yes - what conclusions did you come to? I have had a previous Internal Voltage Regulator failure with this same Alternator which was repaired. I believe the previous failure may have been caused by turning on the alternator switch after start up. Ever since that point I have been turning on the Alternator switch prior to start up and turning off after shutdown. My Engine/Alternator has now done 193 hours. Any help/thoughts would be appreciated because when I fly back to pick up my RV I want to be confident that I can get it home. All the rest of this narrative is irrelevant to the core issues illustrated. This story isn't about resolving an alternator problem, it's about lack of SYSTEM reliability. Bob . . . ________________________________ Message 8 _____________________________________ Time: 10:05:53 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: DIY CBOVM: variations on a theme At 10:23 AM 3/26/2014, you wrote: >Joe, > >1. How much power can the dynamo produce? Most are limited to about 30A. The single phase (2-wire) offerings by B&C, Rotax and others are in the 8-20A class. The 3-phase, 3-wire devices for the larger 'tractors' can get you 30A or so. The problem with PM alternators is not the power generating ability of the mechanism but the power handling ability of the rectifier/ regulator. Unlike the 3-phase automotive alternator that runs output power through simple junction diodes. The regulator carries only a couple amps of field current. In the PM regulator, total output current of up to 30A flows through regulator semiconductors. Hence the heat sinks and limited size with respect to power. Bob . . . ________________________________ Message 9 _____________________________________ Time: 10:26:53 AM PST US Subject: AeroElectric-List: Re: DIY CBOVM: variations on a theme From: "user9253" Ken, Thanks for suggesting the capacitors. The circuit is stable unless the voltage gets very close to the trip point. That is OK with me as long as there is no nuisance tripping. Time will tell. Good point about the crowbar circuit acting immediately by clamping the supply to ground. The data sheet for my relay says it will operate in 15 milliseconds. I am hoping the battery will limit the voltage until the relay contacts open. I will try to land before the battery runs down enough (almost completely dead) to drop out the relay. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=421078#421078 ________________________________ Message 10 ____________________________________ Time: 10:59:58 AM PST US From: K Subject: Re: AeroElectric-List: Re: DIY CBOVM: variations on a theme Joe 600 hours on two of the OVMs and never a nuisance trip. Have had a real trip on the Dynamo one when I started up with one of my two small Z-14 AGM batteries dead. The totally dead battery wouldn't accept current and the John Deere regulator immediately failed full on. The battery did eventually charge but initially it would not accept current. Note to self - if I leave a switch on by mistake for a week and can't charge the battery first - at least run with that alternator off and the batteries paralleled to the other alternator for awhile with engine speed low enough to keep the charge current reasonable. Ken do not archive On 26/03/2014 1:23 PM, user9253 wrote: > > > Ken, Thanks for suggesting the capacitors. The circuit is stable > unless the voltage gets very close to the trip point. That is OK > with me as long as there is no nuisance tripping. Time will tell. > Good point about the crowbar circuit acting immediately by clamping > the supply to ground. The data sheet for my relay says it will > operate in 15 milliseconds. I am hoping the battery will limit the > voltage until the relay contacts open. I will try to land before the > battery runs down enough (almost completely dead) to drop out the > relay. Joe > > -------- Joe Gores > > ________________________________ Message 11 ____________________________________ Time: 12:43:13 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: The lithium saga slogs onward . . . FIY . . . got a peek inside this battery from True Blue Power . . . who has achieved the first TSO'd offering for GA aircraft. http://tinyurl.com/lxh6wqm The battery is 17Ah (in AIRCRAFT Ah at 1-hour - not a 20 hour rate) and 24V. Weighs about 16 pounds. So a 12v, 17Ah battery would be about half that weight. TB17 This battery is an array of 56 cylindrical cells not unlike these 26650 cells available from a variety of sources. 1pc 3.2V LiFePO4 Li-ion LFP26650 energy type 3200mAh flat cap b In rough numbers, this cell is a 10Wh storage medium. 56 cells x 10Wh suggests you can expect about 560Wh from the array. This is consistent with nameplate energy rating for the battery at 430Wh. Being one of the few batteries where detailed system integration data are available, we can begin to size the task for incorporation of this or similar products into airplanes. A 12V version of the battery would be 215Wh so if you have an electrically dependent engine with a 100W service load, you could expect about 2 hours endurance for just an engine. Peel off 50-73 watts for electro-whizzies, your battery only endurance expectations are just over 1 hour for new battery, just under 1 hour for end-of-life battery. Now for the sobering facts. There are two circuit boards in the battery management system (BMS). One is just under the heat-sink fins on top of the battery. It's populated with a goodly number of FAT transistors, probably N-MOS FETs in TO-247 plastic packages. The other board occupies a whole side of the battery and is covered with perhaps 2-3 dozen surface mount ic's and lots of jelly-bean parts. There's probably more silicon in this battery than in your ICOM comm transceiver, gps and transponder combined. Further, I believe this battery will sell for about $3200; so one might ball-park a 12v battery at $1600. Of course, that's 'airplane' pricing that carries the burden of TSO certification. This product is the leading edge example of what it takes to get approval for TC aviation. Other product MIGHT offer similar capabilities for $less$ if they've not run the TSO gauntlet. Just giving you guys a heads-up on what I'm discovering as that battery articles move forward . . . The REAL significance of this discovery exercise is that to get 1-hour of battery only endurance in a 200W airplane will take an array of 28 lithium cells of the size cited above. This means that batteries like this [] http://tinyurl.com/k8yhurl which are 4 x 4 arrays of similar cells probably fall short of the 1-hour endurance hypothetical half-a-True-Blue endurance cited above. Further, this pretty little red thing cannot feature the same degree of battery management that's built into the True Blue product. Tying this back to the venerable PC680 . . . Emacs! We see that teh PC680 at the 1-hour rate is a 12.3Ah battery when new. A 175W airplane will say lit up for about 45 minutes on a new battery. Bob . . . ________________________________ Message 12 ____________________________________ Time: 12:47:09 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: DIY CBOVM: variations on a theme At 11:45 AM 3/26/2014, you wrote: > >In regards to stability you might check that there is a capacitor >across the voltage reference diode and another from the SCR gate to >ground. If you happen to have an old circuit diagram dated before >about 2005 it may not show that update. > >One nice thing about the crowbar and circuit breaker in the Z >diagrams is that the voltage is brought under control immediately >when the SCR fires. If I understand your post it sounds like your >implementation waits for the relay to open and for any subsequent >arcing to extinguish. Perhaps that is good enough but it seems >preferable to use the circuit breaker as per the Z diagrams so that >the SCR clamps the voltage faster. Might be other small advantages >as well such as a subsequent dead battery could not cause the >alternator to come back on line. For the run-of-the-mill ov conditions with a good battery, an ov even is not one of extreme urgency. The ships air-worthy battery will stand off a runaway alternator for significant intervals. If one waited 100 mS to evaluate an ov condition for a true runaway alternator, it wouldn't be a bad thing. In fact, the next generation ov module will do just that. Sensing an ov condition start a 100mS timer that continue to run as long as the voltage does not drop back below 16V before the timer runs out. On the other hand, a second threshold at 20V assumes no air worthy battery is present and an immediate trip is initiated. We're still going to pull down on the field supply breaker . . . 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.