VERY LIGHT BATTERIES

Discussion in 'General Experimental Aviation Questions' started by oldcrow, Jan 16, 2020.

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  1. Jan 17, 2020 #21

    oldcrow

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    if all motors are ac motors then explain how the dc to ac converter works with this motor

     
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  2. Jan 17, 2020 #22

    12notes

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    My plane won't have an alternator.

    There are cheaper LiFePO4 batteries with integrated controllers other than EarthX. Even the random one I linked to earlier had an integrated battery management system that has overcharge protection among other things and you simply hook it up where the old battery was.

    The batteries don't exist only for plane usage. I was pointing out that more powerful LiFePO4 batteries exist, nothing more. Not sure why you felt the need to argue that they are not needed to start an engine, when there are engines that do need it.

    But since you asked, there are a lot of Experimental - Exhibition warplanes with larger engines, so I'll say a T-6 Texan. Is an P&W R-1340 big enough?

    Some people actually know what they're talking about.
     
  3. Jan 18, 2020 #23

    pwood66889

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    "explain how the dc to ac converter works with this motor"
    Hmmm... Looks like the phrase "Laboratory Curiosity" personified. Would love to have the schematic to study!
    Got it! Magnets on the bottom of the battery.
     
    Last edited: Jan 18, 2020
  4. Jan 18, 2020 #24

    Aerowerx

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    It has to do with the current through the wire creating a magnetic field at an angle to the field from the magnet.

    Same thing as in a "real" motor. The magnetic fields in the rotor and stator are not in alignment, so the rotor moves to align the field. But by then the field has changed (AC remember), so the process repeats.
     
  5. Jan 18, 2020 #25

    pictsidhe

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    That is a unipolar motor. They aren't very practical. It gets very difficult having multiple turns
     
  6. Jan 18, 2020 #26

    Jerry Fischer

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    I wonder what the tariff is on those "Chinese" batteries? Hope it's high...
     
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  7. Jan 20, 2020 #27

    dog

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    there are very light "super capistor" batterys on the market now,though the tariff could be high right now,depending on where you live,the supper capicitor batterys are best for starting loads,huge curent,for running other stuff a second battery of different chemistry ,there are dozens of competeing ideas in the market and the language used in the discussions is hard to follow as batterys are multi disiplinary, chemistry,physics,material sciences,electronics, and lately,quantum physics,plus whatever I am forgetting to add.
    Lead carbon anyone,lithium air,flow batterys, alchol powered micro turbines?
    Throw in things like the idea if a starterless ICE, where the compter knows which cylinder is positioned just so,injects just the right bit of fuel,
    and zapps the plug and off it goes.
    loose the starter,heavy battery,heavy cables,and run a much smaller alternator,its been done,just not comercialized
    And then find the right light battery.
     
  8. Jan 20, 2020 #28

    Dan Thomas

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    That was an old Model T trick. Crank the engine a couple of turns to draw in a little fuel, and position the crank with a piston just past TDC, then hit the ignition buzzer, which would fire the plug and start the engine. But the problem is that the combustion chamber is really small at that point, the air leaks away past the rings, and it takes the tiniest amount of fuel to stay in the combustible range or you'll flood it. A computerized system would have to look for a piston a third of its way down the stroke to make that work well enough to kick the engine over against the higher compressions used now. And pistons are rarely cooperative in stopping just where you want them.
     
  9. Jan 20, 2020 #29

    dog

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  10. Jan 20, 2020 #30

    bmcj

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    Yeah, but the ratio of battery weight to total weight on this aircraft is terrible! :p
     
  11. Jan 21, 2020 #31

    Dan Thomas

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    It won't work. The magneto's points open well before TDC, with the impulse couple bringing that close to TDC, and after that the distributor spark finger isn't anywhere near the spark lead terminal, making the idea unworkable. Besides that, the compression leaks away when you leave the piston at any spot on the compression or power strokes, leaving little in the way of combustion energy. I looked at doing this ten or 12 years ago on my A-65. The Model T had a manual timing control that could physically retard the entire magneto far enough to make it work. Your A-65 doesn't.

    100 pounds by removing starter and battery? Nope. Starter is around 20 or 25 pounds, lightweight starters maybe five pounds lighter. Battery is 21 pounds for a 25 amp-hour lead-acid battery. Total less than 50 pounds.
     
  12. Jan 21, 2020 #32

    pictsidhe

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    I've accidentaly spun a few engines over a few revs while tinkering with the ignition. It's something I am aware of when messing with old carb and points engines... All were singles.
     
  13. Jan 21, 2020 #33

    dog

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    Ok
    Add the flywheel and anything else?, I am missing?
    not a hundred ,still in the zone of interest at 50 lbs

    And as to the idea of a starterless start(I will work in a light weight battrery some how),what occured was a seperate circuit to fire one or two plugs in sucession that had nothing to do with the stock mag ignition, extra spark plug leads,so, prime,fuel on,pull through, mags on,press the button and a spark is generated at # 1, should the prop do turning,then a hall sensor controls firing a second time for #3,mags are now doing there thing, and zappy is go?a proptotype could be a mechanical pencil sharpener modified to open and close some points,a coil, and wire,and dozen tripple AAA,s
    Oh yes and as the plane would not need a big heavy
    battery with the ability to deliver a huge starting current, a light battery, even very light that had more of a deep cycle character could run the starter coil
    for 3 seconds and a light or something.
     
  14. Jan 22, 2020 #34

    Dan Thomas

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    A dozen AAA's won't run a coil, which requires on the order of around 7 amps. Physics is so inconvenient at times...
     
  15. Jan 22, 2020 #35

    dog

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    I did not know that coils were that inificient.
    80 or a hundred watts, spose thats why it hurts to grab a live plug wire.
    Anyhow those tripple AAA's come in pack of 30
    at wally world for 8bucks , a cordless drill battery
    100watt flex solar panel,supper light,thin and will
    conform to a curve,sometimes known as a solar
    battery.Some form of very light battery, and a pencil sharpener,jb weld,etc,etc and zappy is a go
    physics is fun and I am realy hoping this works, time to move a few things around and mount the a-65 to the fuselage,missing one an bolt for the motor mount.
    Why I built a trolley crane n all.Need some av gas
     
  16. Jan 22, 2020 #36

    Pops

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    Friend of mine flew a Mini-Max with a 1/2 VW for over a thousand hours. Used a VW distributor and coil and a 12Volt X 5 amp model airplane starting battery for 2 hrs of flight time and the volt meter would be down to 10 volts when flying the 2 hrs and if still flying he switched to 8-- D cell flashlight batteries and landed as soon as possible. Never had to make an off field landing. Engine burned 1.7 GPH, I know because he always got a free fill-up when he flew to my place. Big spender :)
     
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  17. Jan 23, 2020 #37

    Aerowerx

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    It's the current that you feel, not the power.

    The higher the voltage the easier it is for the current to literally get under your skin and reach those nerve endings. A typical spark coil is what? 20,000 volts? Now if the voltage is high enough your skin will get charred and once the current gets to your body fluids it has pretty much a short circuit, and the current goes way up.
     
  18. Jan 23, 2020 #38

    lr27

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    I think the original poster was talking about starter batteries. If using in a 12 volt vehicle, 4 LiFe batteries in series will get at least a partial charge unless you set the vpltage regulator higher. And then you need a fancy charger, etc. I have an RC glider with a self launching motor that used only 2 cells, each about 2.5 ounces, in series, with a nominal voltage of 3.2 . The pack was putting out 50 or 60 amps.

    By now, I think some flavors of lithium ion can put out as much current for the weight, though ratings for the hobby market should probably go in the fiction section. The lithium batteries, of course, can store more energy for the weight. I imagine they're making progress on safety, which I think is where LiFe batteries are supposed to have an advantage. I met someone who lost his house when he was a bit careless about charging lipos. (lithium ion in flexible case)
     
  19. Jan 23, 2020 #39

    dog

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    Right.And following the thought ends up at chain link fence topped with barbed wire, and little enameled signs saying warning HIGH VOLTAGE.
    The storys linesmen tell are not for the faint of heart.
    While tinkering with a solar panel array, in the basement,I inadvertently struck an arc,which was
    self sustaining,say 8 or 9 amps at 90 or 100 volts.
    Big fat blue arc,half an inch long or more.
    The start of this thread is relevant to my project, as
    the a-65 has no alternater or starter, and electrical power of some sort will probably be a requirement
    from the MD-RA.
    As has been pointed out the a-65 with a metal prop
    is not going to leave a large margin for power.
    So the lightest possible battery and electronics.
    I am rapidly becoming a didgital convert and will
    be leaving most of the traditional instrunents on the shelf and making a new panel.
    What comes to mind is a to actualy eliminate the
    "panel" and have a series of tablet and phone mounts or slots, plus a strip for compass,ball,oil pressure,and a pocket for a battery,flex solar panel over head.
    My personal experience with cordless tool,lithium
    batteries, has been that they fail,suddenly, and no not buying junk,top of the line stuff.
    The older nickle cadmium batteries dont have the power density but I have some that are still good, decades old at this point and going strong.
    "sho-me"flashlight in particular ,was stupid expensive, the unit is realy a statement/question/coment about battery technology in general at this point.
    Big unit,with a small head light for the bulb,
    used ,abused,neglected,indifferently charged and
    still goes strong.
    That is the kind of review I am looking for in a very light battery for aviation use.
    The bugaboo with the lithium batteries is "dendrite growth" or simply, they grow crystals that physicaly
    break the internal structure of the batteries.
    Currently there is a very large effort world wide to
    eliminate this problem, with many novel solutions
    working in labs currently.One of the most interesting uses light to effect the ion tranfer internaly,not that I am qualified to disertate on
    quantum physics,but its still fun.
     
  20. Jan 23, 2020 #40

    Dan Thomas

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    AAA alkaline batteries are rated at about 10 milliamps for a constant-current application, and 1000 milliamp-hours. That means, theoretically, that the AAA can provide one amp for one hour, and I bet not many folks have gotten anything like that out of one. The D-cell, by contrast, supports a 200 mA drain and 13000 mAh, 20 times the AAA for the drain and 13 times for the Amp-hour. AAAs are tiny, which should give one a clue.

    A coil takes a low voltage and rather high amperage supply and converts it to a very high voltage and very low amperage delivery for a spark. That's why coils need so much current--because their input voltage is low. If you needed 7 amps and 12 volts for the coil, using the optimistic 1000mAh rating for the AAA, you'd need 56 AAAs to get the job started, wired in series-parallel, and the spark wouldn't last very long. The D-cells required would be much less, with 8 of them wired in series providing a theoretical 13 amps (13000 mAh) at 12 volts and so lasting much longer than the AAAs.
     
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