---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 05/18/09: 17 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:21 AM - Re: LR3 regulator Amperage indications (Bill Schertz) 2. 06:42 AM - 12 Volt .vs. 24 Volt (Brooke Wolf) 3. 07:25 AM - Re: 12 Volt .vs. 24 Volt (Bruce Gray) 4. 08:33 AM - Re: 12 Volt .vs. 24 Volt (Peter Laurence) 5. 08:33 AM - Re: Re: EXP2BUS and non-functioning alternator (Ian) 6. 09:30 AM - Re: 12 Volt .vs. 24 Volt (David LLoyd) 7. 10:03 AM - Re: 12 Volt .vs. 24 Volt (ROGER & JEAN CURTIS) 8. 11:16 AM - Speaking of W-R/RBM/Stancore Contactors . . . (Robert L. Nuckolls, III) 9. 11:29 AM - Re: 12 Volt .vs. 24 Volt (Robert L. Nuckolls, III) 10. 11:53 AM - Re: 12 Volt .vs. 24 Volt (BobsV35B@aol.com) 11. 01:44 PM - Re: 12 Volt .vs. 24 Volt (Steve Thomas) 12. 02:40 PM - Re: 12 Volt .vs. 24 Volt (Bruce Gray) 13. 06:00 PM - Re: Modifying the Piper plug (woxofswa) 14. 06:12 PM - Re: 12 Volt .vs. 24 Volt (Rick Titsworth) 15. 07:25 PM - Re: 12 Volt vs. 24 Volt (Robert L. Nuckolls, III) 16. 07:26 PM - Re: Re: Modifying the Piper plug (Robert L. Nuckolls, III) 17. 08:38 PM - Re: 12 Volt vs. 24 Volt (joe motis) ________________________________ Message 1 _____________________________________ Time: 04:21:29 AM PST US From: "Bill Schertz" Subject: Re: AeroElectric-List: LR3 regulator Amperage indications Bob, I am now convinced that the variations were real. I inserted an ammeter into the field line, while the engine was stopped. Got a reading of 3.5 amps. Then took the plane out, fired it up with the ammeter in place, and when the alternator switch was turned on, the current went to 3.5 amps for a very short time, then dropped to zero. At that point, it stayed at zero, and the battery would not charge. Put plane back in hanger, and did some static measurements. Voltage from LR-3 to field circuit breaker ~4.5 volts Voltage at connector to alternator (black plug) ~4.5V Resistance to ground through the leads that field current plugs into varies (jumps around) and then often goes to open circuit. Could the slip rings be contaminated or not in contact? Comments? Bill Schertz KIS Cruiser #4045 N343BS Phase I testing ----- Original Message ----- From: "Robert L. Nuckolls, III" Sent: Friday, May 08, 2009 3:31 PM Subject: Re: AeroElectric-List: LR3 regulator Amperage indications > > > At 10:33 AM 5/8/2009, you wrote: >>Bob, >>The heavy B lead comes off the B&C alternator, and passes through a sensor >>supplied by Blue Mountain avionics, which I believe is a Hall effect >>transducer, and then goes to the Batteries. The Voltage is measured at >>the Main buss. >> >>I am enclosing the output from the last flight showing the variations. > > Those traces are almost certainly plagued with data sampling > artifacts polluted by noise. There's no way that the "real" > numbers are that trashy. Have you explored the R/C filtering > I suggested? How many bits of resolution does the data > acquisition system offer? > > > Bob . . . > > ----------------------------------------) > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > ---------------------------------------- > > > ________________________________ Message 2 _____________________________________ Time: 06:42:55 AM PST US From: Brooke Wolf Subject: AeroElectric-List: 12 Volt .vs. 24 Volt I have a feeling that this subject has been discussed before, but I need help deciding on a voltage system for my Velocity. I intend a robust electrical system to support a high end IFR panel. The highest draw item will probably be an electric hydraulic pump which pulls about 30 amps at 12 volts. I know a 24 volt will save some weight in wiring because of the lower amperage. However, after reading Bob's response to a Blue Mountain article http://www.aeroelectric.com/articles/richter/response_1.pdf the weight saved appears minimal. I don't know for sure, but I have a feeling that the vast majority of OBAM airplanes are built around 12 volt systems. My question is, why do the likes of Cessna and Cirrus build their single engine airplanes with 24 volt systems? Thanks...Brooke ________________________________ Message 3 _____________________________________ Time: 07:25:31 AM PST US From: "Bruce Gray" Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt Similarity of construction. Bruce Glasair III (28v) www.Glasair.org -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Brooke Wolf Sent: Monday, May 18, 2009 9:40 AM Subject: AeroElectric-List: 12 Volt .vs. 24 Volt I have a feeling that this subject has been discussed before, but I need help deciding on a voltage system for my Velocity. I intend a robust electrical system to support a high end IFR panel. The highest draw item will probably be an electric hydraulic pump which pulls about 30 amps at 12 volts. I know a 24 volt will save some weight in wiring because of the lower amperage. However, after reading Bob's response to a Blue Mountain article http://www.aeroelectric.com/articles/richter/response_1.pdf the weight saved appears minimal. I don't know for sure, but I have a feeling that the vast majority of OBAM airplanes are built around 12 volt systems. My question is, why do the likes of Cessna and Cirrus build their single engine airplanes with 24 volt systems? Thanks...Brooke ________________________________ Message 4 _____________________________________ Time: 08:33:49 AM PST US From: "Peter Laurence" Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt > I have a feeling that this subject has been discussed before, but I need help deciding on a voltage system for my Velocity. I intend a robust electrical system to support a high end IFR panel. The highest draw item will probably be an electric hydraulic pump which pulls about 30 amps at 12 volts. I know a 24 volt will save some weight in wiring because of the lower amperage. However, after reading Bob's response to a Blue Mountain article http://www.aeroelectric.com/articles/richter/response_1.pdf the weight saved appears minimal. I don't know for sure, but I have a feeling that the vast majority of OBAM airplanes are built around 12 volt systems. My question is, why do the likes of Cessna and Cirrus build their single engine airplanes with 24 volt systems? Thanks...Brooke I wired a Velocity XL RG for a friend as a 12v system. Dual B&C alternators and Regulators. No issues for over four years and five hundred hours. Peter ________________________________ Message 5 _____________________________________ Time: 08:33:49 AM PST US Subject: Re: AeroElectric-List: Re: EXP2BUS and non-functioning alternator From: Ian Bob, I have the installation manual (attached) but it doesn't have a conventional circuit diagram. There is a logical layout in Figure 7, and a physical layout in Figure 3 (the IRF4905 is at J17) and a photo on the front page, which also shows it's location. There is evidence that the track leading from the Source pin on the IRF4905 has overheated, but I have yet to check it for continuity (meter is at the airport). Ian On Sun, 2009-05-17 at 21:31 -0500, Robert L. Nuckolls, III wrote: > > At 05:08 PM 5/16/2009, you wrote: > > > >I discovered that the IG lead to the alternator was only producing > >12V when measured disconnected. As soon as a load was applied that > >went down to 1.5V. It turns out that some filings had got under > >the legs of an IRF4905 Mosfet and seemed to have shorted the pins. > > > >So, new question: Does anyone know how to test whether the cleaned > >up IRF4905 still works, and what the pinouts might be. There are > >three legs, but nothing I've read tells me what leg does what. > > See: > > http://www.irf.com/product-info/datasheets/data/irf4905s.pdf > > > >Would I have to remove the IRF4905 from the board to test it's output? > > I wouldn't think so . . . but I'm mystified as to how > an IRF4905 might be used to control an alternator. This > is a really husky device. Far larger than necessary > to effect control of the IG lead of an alternator. Do > you have a schematic of the EXP2BUS product? I wasn't > able to find anything useful on the website. > > > Bob . . . > > ----------------------------------------) > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > ---------------------------------------- > > > > > > ________________________________ Message 6 _____________________________________ Time: 09:30:42 AM PST US From: "David LLoyd" Subject: Re: AeroElectric-List: 12 Volt .vs. 24 Volt Why 24 v. systems.... in the commercial world it is usually about costs and profits. Less copper used, less cost. David ----- Original Message ----- From: "Bruce Gray" Sent: Monday, May 18, 2009 7:01 AM Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt > > Similarity of construction. > > Bruce > Glasair III (28v) > www.Glasair.org > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of > Brooke Wolf > Sent: Monday, May 18, 2009 9:40 AM > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: 12 Volt .vs. 24 Volt > > > I have a feeling that this subject has been discussed before, but I > need help deciding on a voltage system for my Velocity. I intend a > robust electrical system to support a high end IFR panel. The highest > draw item will probably be an electric hydraulic pump which pulls > about 30 amps at 12 volts. I know a 24 volt will save some weight in > wiring because of the lower amperage. However, after reading Bob's > response to a Blue Mountain article > > http://www.aeroelectric.com/articles/richter/response_1.pdf > > the weight saved appears minimal. I don't know for sure, but I have a > feeling that the vast majority of OBAM airplanes are built around 12 > volt systems. My question is, why do the likes of Cessna and Cirrus > build their single engine airplanes with 24 volt systems? > > Thanks...Brooke > > > ________________________________ Message 7 _____________________________________ Time: 10:03:30 AM PST US From: "ROGER & JEAN CURTIS" Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt Similarity of construction. (Please elaborate!) Bruce Glasair III (28v) www.Glasair.org I have a feeling that this subject has been discussed before, but I need help deciding on a voltage system for my Velocity. I intend a robust electrical system to support a high end IFR panel. The highest draw item will probably be an electric hydraulic pump which pulls about 30 amps at 12 volts. I know a 24 volt will save some weight in wiring because of the lower amperage. However, after reading Bob's response to a Blue Mountain article http://www.aeroelectric.com/articles/richter/response_1.pdf the weight saved appears minimal. I don't know for sure, but I have a feeling that the vast majority of OBAM airplanes are built around 12 volt systems. My question is, why do the likes of Cessna and Cirrus build their single engine airplanes with 24 volt systems? Thanks...Brooke ________________________________ Message 8 _____________________________________ Time: 11:16:32 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Speaking of W-R/RBM/Stancore Contactors . . . FYI . . . I've become aware of a failure internal to a 3-terminal White-Rogers/RBM Controls contactor that shorted the coil stud to the contactor's floating conductor ring. This caused the contactor to "buzz" and ultimately burned the wire between the contactor and the battery master switch. Artifacts of arcing are visible in: http://aeroelectric.com/Pictures/Failures/W-R_RBM_3-Terminal_2s.jpg The solder lug that attaches to the coil wire is oriented UP toward the conductor ring and then formed over for clearance. At first blush, I would suspect that this solder lug was improperly assembled at the factory . . . it could have been laid over 90-degrees and still provided for coil lead termination with MUCH more clearance to the fat copper conductor ring. To understand the internal construction of this product I'll refer the readers to images at: http://www.aeroelectric.com/Pictures/Contactors/S701-1a.jpg http://www.aeroelectric.com/Pictures/Contactors/S701-1b.jpg http://www.aeroelectric.com/Pictures/Contactors/S701-1c.jpg http://www.aeroelectric.com/Pictures/Contactors/S701-1d.jpg http://www.aeroelectric.com/Pictures/Contactors/S701-1e.jpg http://www.aeroelectric.com/Pictures/Contactors/S701-1f.jpg These photos are for a later configuration of the 3 and 4- terminal contactors. The tiny coil wire is not even visible and ample clearances are maintained between coil terminal hardware and conductor ring by a molded nylon terminal housing. The 'Connection (and to the best of my knowledge B&C) has never sold contactors with the earlier terminal configuration. The failed contactor had a date code of 9515; 15th week of 1995). Every 4-terminal device I've torn down featured later configuration for coil terminals visible in photos above. It's also a fair bet that older versions of the contactor described in the failure analysis were assembled with more attention to detail for positioning the solder lug. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 9 _____________________________________ Time: 11:29:42 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 12 Volt .vs. 24 Volt At 10:44 AM 5/18/2009, you wrote: > >Why 24 v. systems.... in the commercial world it is usually about >costs and profits. Less copper used, less cost. >David > Close. When I went to work for Cessna in '64, we had 14v airplanes (150, 172) and 28v airplanes (182, 206, 210). When you need to run high-energy electro-whizzies you can get more WATTS of engine driven power from essentially the same WEIGHT of system if it's 28v. But as quantities of all airplanes sold dwindled, it was economically more efficient to simply install the same hardware in all aircraft. The alternators were the same size and weight, batteries could be sized to the task for total energy stored. Common landing lights, nav lights, strobe kits, etc made for fewer line items of electrical goodies in inventory and more wider applicability of fewer parts for field spares. It had nothing to do with any practical level of weight savings. We kinda like 14v stuff in the OBAM market: unlike the uniquely aircraft "pallet of paints" for 28V hardware, 14V automotive hardware is stocked in thousands of varieties and sources virtually everywhere on the planet. The "improved performance" and "lighter weight" canards are difficult to measure/prove without carefully detailed studies with slice-n-dice instrumentation. For us get-in-n-go airplane drivers, the 14 vs. 28 volt differences are not readily observable. So the big driver is simply cost of ownership in terms of $acquisition$ and $time$ to maintain. 14v has it hands down. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 10 ____________________________________ Time: 11:53:41 AM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: 12 Volt .vs. 24 Volt Good Afternoon, Definitely NOT 'Lectric Bob here! I DO like twenty-four volt systems. I also agree that any weight saving is probably minimal on an overall basis, nevertheless, I do subscribe to the theory that ounces count. Twenty-four volts allows us to use lighter weight starters, alternators, wires, even relays. The trouble is that most twenty-four volt units weigh as much as their twelve volt counterparts. If you want to take full advantage of a twenty-four volt system you also have to use lighter components. If thirty amps at twelve volts will handle all of your aircraft requirements, all you need is fifteen amps with a twenty-four volt system. How many fifteen amp alternators do you see available? If you go ahead and use a thirty amp twenty-four volt alternator, you have not taken full advantage of the weight saving capabilities of the twenty-four volt regime. Cessna went to twenty-four volts for everything from the 152 on up many years ago. It was cheaper and lighter for the whole fleet and only having to deal with twenty-four volt components made inventory control a lot easier. Commonality of parts and all of the economies that breeds! If you want to be able to jump start your airplane form a twelve volt car, twenty-four volts may not be for you. Personally, If I ever have the feeling that I need a jump start for my airplane, I would also determine that I had made some sort of error in managing my flying machine. If I leave the master on and deplete the battery, I will pull the battery, have it properly serviced, and chalk the experience up to my own stupidity. (I have, unfortunately for me, had to do that more than once.) What I have NOT done, however, is jump start my airplane! If I need the battery at all, I want it to be fully charged and properly serviced before I fly. Happy Skies Old Bob AKA Bob Siegfried Ancient Aviator 628 West 86th Street Downers Grove, IL 60516 630 985-8502 Stearman N3977A Brookeridge Air Park LL22 In a message dated 5/18/2009 12:07:06 P.M. Central Daylight Time, mrspudandcompany@verizon.net writes: Similarity of construction. (Please elaborate!) Bruce Glasair III (28v) www.Glasair.org I have a feeling that this subject has been discussed before, but I need help deciding on a voltage system for my Velocity. I intend a robust electrical system to support a high end IFR panel. The highest draw item will probably be an electric hydraulic pump which pulls about 30 amps at 12 volts. I know a 24 volt will save some weight in wiring because of the lower amperage. However, after reading Bob's response to a Blue Mountain article http://www.aeroelectric.com/articles/richter/response_1.pdf the weight saved appears minimal. I don't know for sure, but I have a feeling that the vast majority of OBAM airplanes are built around 12 volt systems. My question is, why do the likes of Cessna and Cirrus build their single engine airplanes with 24 volt systems? Thanks...Brooke **************A Good Credit Score is 700 or Above. See Yours in Just 2 Easy Steps! =Mayfooter51809NO115) ________________________________ Message 11 ____________________________________ Time: 01:44:16 PM PST US From: Steve Thomas Subject: Re: AeroElectric-List: 12 Volt .vs. 24 Volt And don't forget to add that you can save much more weight in the operation of your aircraft by going on a diet! Drop 10 to 15 pounds off your personal frame and it will make up for many many incremental weight saving devices in your airframe. Steve ________________________________________________________________________ On May 18, 2009, at 11:23 AM, Robert L. Nuckolls, III wrote: > The "improved performance" and "lighter weight" > canards are difficult to measure/prove without > carefully detailed studies with slice-n-dice > instrumentation. For us get-in-n-go airplane > drivers, the 14 vs. 28 volt differences are > not readily observable. So the big driver is > simply cost of ownership in terms of $acquisition$ > and $time$ to maintain. 14v has it hands down. > > > Bob . . . ________________________________ Message 12 ____________________________________ Time: 02:40:10 PM PST US From: "Bruce Gray" Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt Sorry, poor choice of words on my part. What I meant was "Commonality of Manufacturing". It easier for the factory to use one battery, one relay, one bulb, one starter, across the entire line than a mixed bag for each different aircraft. Where 28v has 14v beat is in delivery of power. I remember flying my 14v C177RG at night with everything, including all the lights turned on. When I reached for the gear lever and flipped it down, everything went dim! Just about every 14v RG airplane I've flown does that. Not the 28v ones, just the 14v. Power, when you need it, you need it! Bruce www.Glasair.org -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] Sent: Monday, May 18, 2009 10:58 AM Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt Similarity of construction. (Please elaborate!) Bruce Glasair III (28v) www.Glasair.org I have a feeling that this subject has been discussed before, but I need help deciding on a voltage system for my Velocity. I intend a robust electrical system to support a high end IFR panel. The highest draw item will probably be an electric hydraulic pump which pulls about 30 amps at 12 volts. I know a 24 volt will save some weight in wiring because of the lower amperage. However, after reading Bob's response to a Blue Mountain article http://www.aeroelectric.com/articles/richter/response_1.pdf the weight saved appears minimal. I don't know for sure, but I have a feeling that the vast majority of OBAM airplanes are built around 12 volt systems. My question is, why do the likes of Cessna and Cirrus build their single engine airplanes with 24 volt systems? Thanks...Brooke ________________________________ Message 13 ____________________________________ Time: 06:00:40 PM PST US Subject: AeroElectric-List: Re: Modifying the Piper plug From: "woxofswa" Bob, I am going to mount the receptacle close to the battery and run a #4awg right to the battery ground. As such, would the brass plate washer still be advised? Thanks for all your help. -------- Myron Nelson Mesa, AZ Emp completed, legacy build fuse in progress Read this topic online here: http://forums.matronics.com/viewtopic.php?p=244565#244565 ________________________________ Message 14 ____________________________________ Time: 06:12:38 PM PST US From: "Rick Titsworth" Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt If you're thinking heated prop, Elec air conditioning, Elec cabin heat, heated seals, or other high-energy goodies, then a 24V system/alternator offers twice the "power" for roughly the same system weight as a 12v alternator. It's not the (potential) smaller wire savings that is significant/relevant, rather it's twice the available power from the same weight alternator, contactors, etc (i.e. the heavy items). This is also perhaps a consideration if you're planning on a small backup (B&C type) alternator. The 24v version again has twice the available "power" as the 12v (same weight/package) - i.e. more things you can drive on the E-bus. It used to be that 24V goodies were hard to come by. However, an evening with an aircraft spruce (or west marine) catalog will revel that many common items are now available 12v or 24v (14/28) for the same price. More over, most modern avionics items now operate over the entire 12-28 range. With some "shopping", perhaps the only items that needs converting down to 12v is the cigarette lighter port and Ray Allen trim tab servos. .02 -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Monday, May 18, 2009 2:24 PM Subject: Re: AeroElectric-List: 12 Volt .vs. 24 Volt At 10:44 AM 5/18/2009, you wrote: > >Why 24 v. systems.... in the commercial world it is usually about >costs and profits. Less copper used, less cost. >David > ________________________________ Message 15 ____________________________________ Time: 07:25:38 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: 12 Volt vs. 24 Volt At 08:06 PM 5/18/2009, you wrote: If you're thinking heated prop, Elec air conditioning, Elec cabin heat, heated seals, or other high-energy goodies, then a 24V system/alternator offers twice the "power" for roughly the same system weight as a 12v alternator. It's not the (potential) smaller wire savings that is significant/relevant, rather it's twice the available power from the same weight alternator, contactors, etc (i.e. the heavy items). Which reminds me of advice I've offered in years past but worth repeating again: The first task for crafting your electrical system is to craft a load analysis. If your maximum cruising load is expected to exceed 1000 watts, then PERHAPS a 28v system is called for. In the past 20 years, I've been directly involved in crafting only two 28v OBAM aircraft. One was a LongEz where the owner wanted to fly a lot in the northern climes. A 100 amp, 28v alternator was included to over about 200 watts of energy to run the airplane . . . and 2,000 watts for toe heaters! The other was a Lancair IV with electrically driven air conditioning. But even this system pretty low duty cycle. For all the weight, cost and complexity of an air conditioner, it operates an average of 30 minutes per flight cycle in hot weather. The rest of the time, it was dead weight. The 14/28 debate really isn't a debate if you need the energy. But with continuing advances in LED lighting, LCD under glass instruments, etc the energy required to run the vast majority of the OBAM fleet has been going down. It's a rare airplane that needs more than 500 watts (40A at 14v) continuous running loads. Up to twice that load is easily carried by modern automotive alternators. There are a lot of cars coming off the line these days with 100+ amp alternators on them. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 16 ____________________________________ Time: 07:26:19 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Modifying the Piper plug At 07:58 PM 5/18/2009, you wrote: > >Bob, > >I am going to mount the receptacle close to the battery and run a >#4awg right to the battery ground. As such, would the brass plate >washer still be advised? Some kind of backing plate is called for. You need the structural benefits of the backing plate to double up the skin and improve conductivity of the pot-metal jack-housing to cranking currents. But if you want to make it out of aluminum, that's okay too . . . in fact probably better. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 17 ____________________________________ Time: 08:38:02 PM PST US Subject: Re: AeroElectric-List: 12 Volt vs. 24 Volt From: joe motis As more and varied low current draw devices become available, do you see PV in the equation? On Mon, May 18, 2009 at 7:23 PM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > nuckolls.bob@aeroelectric.com> > > At 08:06 PM 5/18/2009, you wrote: > rtitsworth@mindspring.com> > > If you're thinking heated prop, Elec air conditioning, Elec cabin heat, > heated seals, or other high-energy goodies, then a 24V system/alternator > offers twice the "power" for roughly the same system weight as a 12v > alternator. It's not the (potential) smaller wire savings that is > significant/relevant, rather it's twice the available power from the same > weight alternator, contactors, etc (i.e. the heavy items). > > Which reminds me of advice I've offered in > years past but worth repeating again: The > first task for crafting your electrical system > is to craft a load analysis. If your maximum > cruising load is expected to exceed 1000 watts, > then PERHAPS a 28v system is called for. > > In the past 20 years, I've been directly > involved in crafting only two 28v OBAM > aircraft. One was a LongEz where the owner > wanted to fly a lot in the northern climes. > A 100 amp, 28v alternator was included to > over about 200 watts of energy to run the > airplane . . . and 2,000 watts for toe > heaters! > > The other was a Lancair IV with electrically > driven air conditioning. But even this system > pretty low duty cycle. For all the weight, cost > and complexity of an air conditioner, it operates > an average of 30 minutes per flight cycle in > hot weather. The rest of the time, it was dead > weight. > > The 14/28 debate really isn't a debate if you > need the energy. But with continuing advances > in LED lighting, LCD under glass instruments, > etc the energy required to run the vast majority > of the OBAM fleet has been going down. It's a > rare airplane that needs more than 500 watts > (40A at 14v) continuous running loads. Up to > twice that load is easily carried by modern > automotive alternators. There are a lot of > cars coming off the line these days with 100+ > amp alternators on them. > > > Bob . . . > > ----------------------------------------) > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > ---------------------------------------- > > ------------------------------------------------------------------------------------- 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.