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#191
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Is the 787 a failure ?
On Fri, 22 Mar 2013 12:40:50 -0000, "Keith W"
wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 09:23:17 -0000, "Keith W" wrote: The conventional Batteries are sometimes called Sealed Lead Acid Batteries but they are actually AGM batteries. Modern passenger aircraft normally use Nickel Cadmium batteries Why havent they converted over to NmH? They have a relatively high self discharge rate and can lose up to 20% of the energy stored in the first 24 hours. This is acceptable for hybrid vehicles where the battery is primarily a temporary buffer to capture the energy from regenerative braking but not good for a system intended to initiate an aircraft startup sequence after a week in the hangar. Keith Thats not true anymore. Since Sanyo developed the Enerloop NiMH battery..they are being shipped charged from the factories. All the makers are using the new tech and have been doing so for at least 3 yrs. Ive got NiMH batteries that I only need to put on the charger ever 6 months, just to top them off. Gunner |
#192
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Is the 787 a failure ?
Jim Wilkins wrote:
"Mr. B1ack" wrote in message ... Not interested in burning to death over the Pacific .... Better to fall into the South Atlantic because the Airbust didn't inform the pilots that it had stalled. Actually it did, they simply chose to disregard the stall warning that sounded continuously for 54 seconds and the stick shaker. Keith |
#193
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Is the 787 a failure ?
Daryl wrote:
On 3/22/2013 6:09 AM, Keith W wrote: Battery energy density MJ per kilogram Lithium-ion battery 0.720 Alkaline battery 0.671 Nickel-metal 0.28 Lead-acid battery 0.17 The reason the AGM isn't used in larger applications is that it cannot be recharged as it is being discharged. Hmm ISTR that my car alternator can charge the battery and run the lights at the same time so I'd love to know what scenario you had in my mind there You left out a slew that use Deep Cells. Feel free to add them in. IT does the job if you keep it over 50% just like clockwork and can last at least 2 to 5 years without going below 50% charge if you keep them above freezing and below 100 degrees (the same as the Lithiums). I use AGMs on a daily basis and my battery provider says I am the hardest on batteries he's ever seen. I am getting ready to do another build that uses the heavier Deep Cell which is designed to put up with my punishement. But the AGMs are more rugged than the Lithiums that I also use. Nacads also work but for about one run into town before they overheat. Ever seen a Nacad blow up? IT's pretty anticlimatic. They burst and make a mess out of everything around it. And it's caustic. Same goes for a Lithium except they will go into flame and feed the flame until all the liquid is used up. I have never had a case break open on an AGM. I've crashed em, dump em, drop em, used them for Rocky Mountain Offroad, and more. I can see that the Deep Cell Sealed Lead Acid should be as tough and have a longer run time but they are twice as heavy. Which is something of a problem for aircraft Just leave out that 1 six pack of Tomato Juice to make up the difference. It's not a real problem where an extra 10 pounds is really going to make a difference for something the size of the 787. An added 10 pounds for safety sake is very important. Its going to be a lot more than 10 pounds. The lifespan of the Deep Cell the way I use batteries should be as high as the Lithium and cost less. But the weight means only my 3 wheelers will use them. They just don't make 10 to 15 amp deep cells. But they do make a very solid 35 amp at twice the weight and size of a 12 amp AGM. I am just not sold on Lithiums and I am certainly not sold on Nicads. The Airline Aircraft Industry can use the AGMS and have less problems, almost the same run time as the lower Lithium Mag batteries and save a bunch of money. Airbus use NiCads ,the Boeing 737, 747 (pre-800) and 777 use NiCads , they disagree with you. Nicads are old technology. The AGM batter is much newer. When they were designing the 737, 747 and 777 the AGMs weren't available. Single Airplanes use the AGMs and that is more critical for weight and safety than the big birds are. AGM batteries have been around for at least 25 years and Boeing have used them in military aircraft includng the AV8B so that idea wont fly. They were certainly around when the 777 was being designed. I use all these batteries in transporation every day. I am a dealer in the AGMs and the Lithiums as well as the motors and kits. I can also get you a good deal in Deep Cells but the shipping would be a killer. I can buy them locally and have done so for use in towed caravan installations. Keith |
#194
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Is the 787 a failure ?
GunnerAsch wrote:
On Fri, 22 Mar 2013 12:40:50 -0000, "Keith W" wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 09:23:17 -0000, "Keith W" wrote: The conventional Batteries are sometimes called Sealed Lead Acid Batteries but they are actually AGM batteries. Modern passenger aircraft normally use Nickel Cadmium batteries Why havent they converted over to NmH? They have a relatively high self discharge rate and can lose up to 20% of the energy stored in the first 24 hours. This is acceptable for hybrid vehicles where the battery is primarily a temporary buffer to capture the energy from regenerative braking but not good for a system intended to initiate an aircraft startup sequence after a week in the hangar. Keith Thats not true anymore. Since Sanyo developed the Enerloop NiMH battery..they are being shipped charged from the factories. All the makers are using the new tech and have been doing so for at least 3 yrs. Ive got NiMH batteries that I only need to put on the charger ever 6 months, just to top them off. Gunner Trouble is they are not available in the size or capacity to be used in an electric vehicle, last time I checked the largest was a D size. Keith |
#195
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Is the 787 a failure ?
On Fri, 22 Mar 2013 16:57:55 -0000, "Keith W"
wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 12:40:50 -0000, "Keith W" wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 09:23:17 -0000, "Keith W" wrote: The conventional Batteries are sometimes called Sealed Lead Acid Batteries but they are actually AGM batteries. Modern passenger aircraft normally use Nickel Cadmium batteries Why havent they converted over to NmH? They have a relatively high self discharge rate and can lose up to 20% of the energy stored in the first 24 hours. This is acceptable for hybrid vehicles where the battery is primarily a temporary buffer to capture the energy from regenerative braking but not good for a system intended to initiate an aircraft startup sequence after a week in the hangar. Keith Thats not true anymore. Since Sanyo developed the Enerloop NiMH battery..they are being shipped charged from the factories. All the makers are using the new tech and have been doing so for at least 3 yrs. Ive got NiMH batteries that I only need to put on the charger ever 6 months, just to top them off. Gunner Trouble is they are not available in the size or capacity to be used in an electric vehicle, last time I checked the largest was a D size. Keith The Tesla Roadster has 6,831 lithium-ion cells, and each one is between the size of a AA and a C in diameter, but a little longer than either. An AA is 14.5 mm x 50.5 mm. The 18650 Form Factor cells used in the Tesla are 18.6 mm x 65.2 mm. -- Ed Huntress |
#196
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Is the 787 a failure ?
"Keith W" wrote in message
... Jim Wilkins wrote: "Mr. B1ack" wrote in message ... Not interested in burning to death over the Pacific .... Better to fall into the South Atlantic because the Airbust didn't inform the pilots that it had stalled. Actually it did, they simply chose to disregard the stall warning that sounded continuously for 54 seconds and the stick shaker. Keith It sounded for 54 seconds, then it stopped a little after 2h 11m 42s when they were at 35,000 feet, 40 degrees pitch and falling at 10,000 feet/minute. See pages 22 & 23. http://www.bea.aero/en/enquetes/flig...t.final.en.php At 2h 12m ~15s the Pilot Flying made a pitch-down input that brought their forward speed above the stall warning's lower limit of 60 Kts and it sounded again, confusing them. Page 44 of the final report: " If the CAS measurements for the three ADR are lower than 60 kt, the angle of attack values of the three ADR are invalid and the stall warning is then inoperative." My real point is to remind Bill Black that he lives in a glass house and shouldn't throw stones at Boeing. jsw |
#197
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Is the 787 a failure ?
"Daryl" wrote in message
... The method of charging is more complicated than the other versions. NiMH batteries work well if you only have one cell (say, 12 volt using 4 3 volt cells). But when you are trying to generate 36 volts to 400 volts, each cell pack must be independently charged. Not possible in that application. If YOU don't know how then it must be impossible. http://www.mpoweruk.com/balancing.htm "To provide a dynamic solution to this problem which takes into account the ageing and operating conditions of the cells, the BMS may incorporate a Cell Balancing scheme to prevent individual cells from becoming overstressed. These systems monitor the State of Charge (SOC) of each cell, or for less critical, low cost applications, simply the voltage across, each cell in the chain. Switching circuits then control the charge applied to each individual cell in the chain during the charging process to equalise the charge on all the cells in the pack." The balancing circuit is simply a resistor and a FET across each cell to bypass some of the charging current when necessary. The FETs can be optically isolated from the control circuit for high voltage packs. And you haven't seen a burst case either. Bulging, deformed, etc. case but the juice is contained in the case. I sure have, it was displayed as a memorable example of how NOT to design a battery charger. The plate edges were visible through the crack. The reason the AGM isn't used in larger applications is that it cannot be recharged as it is being discharged. You left out a slew that use Deep Cells. Daryl Again, YOU don't know how. A battery monitor circuit that measures current and voltage can model the battery with a custom microcomputer to predict its state of charge and tolerance for charging current, at any point in the discharge cycle. They lose track as the cells age which is why Lithiums need to be periodically fully discharged and recharged, to recalibrate the model. http://www.ti.com/sc/docs/msp/sine_on/batt_mgmt.pdf Look at how much the bq2060 can do for $4.32. Connect it to a PIC and you can record the full service and maintenance history of the battery, like a little Black Box. That's how I know what really hurts Lithiums. jsw |
#198
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Is the 787 a failure ?
Ed Huntress wrote:
On Fri, 22 Mar 2013 16:57:55 -0000, "Keith W" wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 12:40:50 -0000, "Keith W" wrote: GunnerAsch wrote: On Fri, 22 Mar 2013 09:23:17 -0000, "Keith W" wrote: The conventional Batteries are sometimes called Sealed Lead Acid Batteries but they are actually AGM batteries. Modern passenger aircraft normally use Nickel Cadmium batteries Why havent they converted over to NmH? They have a relatively high self discharge rate and can lose up to 20% of the energy stored in the first 24 hours. This is acceptable for hybrid vehicles where the battery is primarily a temporary buffer to capture the energy from regenerative braking but not good for a system intended to initiate an aircraft startup sequence after a week in the hangar. Keith Thats not true anymore. Since Sanyo developed the Enerloop NiMH battery..they are being shipped charged from the factories. All the makers are using the new tech and have been doing so for at least 3 yrs. Ive got NiMH batteries that I only need to put on the charger ever 6 months, just to top them off. Gunner Trouble is they are not available in the size or capacity to be used in an electric vehicle, last time I checked the largest was a D size. Keith The Tesla Roadster has 6,831 lithium-ion cells, and each one is between the size of a AA and a C in diameter, but a little longer than either. An AA is 14.5 mm x 50.5 mm. The 18650 Form Factor cells used in the Tesla are 18.6 mm x 65.2 mm. And a Tesla battery costs between $24,000 and $40,000. The Toyota list price for the Prius battery is $2,299 but aftermarket battery costs start around $1,800 Keith Keith |
#199
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Is the 787 a failure ?
"Keith W" wrote in message
... Ed Huntress wrote: On Fri, 22 Mar 2013 16:57:55 -0000, "Keith W" wrote: The Tesla Roadster has 6,831 lithium-ion cells, and each one is between the size of a AA and a C in diameter, but a little longer than either. An AA is 14.5 mm x 50.5 mm. The 18650 Form Factor cells used in the Tesla are 18.6 mm x 65.2 mm. And a Tesla battery costs between $24,000 and $40,000. The Toyota list price for the Prius battery is $2,299 but aftermarket battery costs start around $1,800 Keith This is a typical price if you want a few to experiment: http://www.amazon.com/Ultrafire-1865.../dp/B006QQ27BW A voltage-and-current controlled lab power supply will recharge them nicely. My 18650 battery holder is a small plastic box with brass screws threaded into the ends as adjustable terminals jsw |
#200
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Is the 787 a failure ?
Jim Wilkins wrote:
"Keith W" wrote in message ... Jim Wilkins wrote: "Mr. B1ack" wrote in message ... Not interested in burning to death over the Pacific .... Better to fall into the South Atlantic because the Airbust didn't inform the pilots that it had stalled. Actually it did, they simply chose to disregard the stall warning that sounded continuously for 54 seconds and the stick shaker. Keith It sounded for 54 seconds, then it stopped a little after 2h 11m 42s when they were at 35,000 feet, 40 degrees pitch and falling at 10,000 feet/minute. See pages 22 & 23. http://www.bea.aero/en/enquetes/flig...t.final.en.php At 2h 12m ~15s the Pilot Flying made a pitch-down input that brought their forward speed above the stall warning's lower limit of 60 Kts and it sounded again, confusing them. Page 44 of the final report: " If the CAS measurements for the three ADR are lower than 60 kt, the angle of attack values of the three ADR are invalid and the stall warning is then inoperative." My real point is to remind Bill Black that he lives in a glass house and shouldn't throw stones at Boeing. jsw The real point is that the aircraft clearly 1) Indicated that it had reverted to direct law (manual input) 2) Sounded the stall warning 3) Showed that the aircraft was falling at a high angle of attack and low speed The pilot flying seems to have been fixated on keeping the wings level and disregarded the angle of attack which at 2 minutes 12 seconds was 40 degrees ! During the entire crisis it was never less than 35 degrees. Keith |
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