Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Results 1 to 9 of 9

  1. #1
    MetallicaJunkie's Avatar
    Join Date
    Sep 2006
    Location
    Donna, TX
    Posts
    5,430
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    Explain this please

    how is this device able to tell how much capacity a LiFe or LiPo has in it from just plugging a battery pack to it? http://www.futaba-rc.com/accessories/futm4166.html
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

  2. #2
    bingo field's Avatar
    Join Date
    May 2004
    Location
    Mt. Morris, NY
    Posts
    1,676
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please

    "*The remaining capacity (criteria) display is based on voltage at no load. Since it may differ largely from
    actual remaining capacity according to the battery type, use it as a criteria only.
    *From the standpoint of the battery characteristics, immediately after charging and discharging, the
    remaining capacity display will change until the battery stabilizes. The voltage stabilizes about 30
    minutes after charging and discharging.
    In addition, because of the different discharge characteristics, when the specified capacity was checked
    after use, a remaining capacity lower than the actual remaining capacity may be displayed even for the
    same type of battery. Judge the remaining capacity with the stable state value as a criteria.
    *When the remaining capacity (criteria) display reaches 20% or less, recharge the battery.
    *When the remaining capacity (criteria) display exceeds 95%, since the battery is almost fully charged,
    refrain from charging it. Overcharging will cause the battery to deteriorate."

    from the manual below



    http://manuals.hobbico.com/fut/br3000-manual.pdf

    if you download the manual, don't freak out because just the first half is in Japanese
    http://www.tailhook.org/AVSLANG.htm
    Sign over Ready Room Door: \"Complacency Kills\" - Thimk

  3. #3
    Moderator CGRetired's Avatar
    Join Date
    Sep 2004
    Location
    Galloway, NJ
    Posts
    8,999
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please

    One other fact to point out is that LiFe packs have a very flat discharge curve with a very sharp knee at the point of exhaustion. This means that the voltage remains fairly constant throughout the discharge process of that pack. For this very reason, devices such as Voltwatch2 and such devices can give you a false sense of security with regard to remaining charge in an LiFe pack. So, use these devices carefully and monitor your flight times.

    It's really best to know how much battery you would consume in a normal flight and base the remaining charge on the overall capacity to determine how many flights you can safely have when starting out with a fully charged pack.

    I am extremely conservative when it comes to flight times and battery duration. I will not fly if I think I am approaching a point where I would be leary of the remaining charge in a pack. There is just to much to lose. Lose the plane, that's one thing. Crash it into a crowd, or into someone's property, well, that's a very different situation and it just isn't worth it to get "one more flight" that day.

    CGr.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  4. #4
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,530
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please


    ORIGINAL: CGRetired

    One other fact to point out is that LiFe packs have a very flat discharge curve with a very sharp knee at the point of exhaustion. This means that the voltage remains fairly constant throughout the discharge process of that pack. For this very reason, devices such as Voltwatch2 and such devices can give you a false sense of security with regard to remaining charge in an LiFe pack. So, use these devices carefully and monitor your flight times.

    CGr.
    Absolutely.

    I've seen posts here from people who INSIST that voltage can be used to determine the charge state of LiPo's, LiFE's, A123's and other Polymer batteries.
    Unfortunately that doesn't really work, because of the relatively flat discharge curves.


    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  5. #5
    MetallicaJunkie's Avatar
    Join Date
    Sep 2006
    Location
    Donna, TX
    Posts
    5,430
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please

    thanks for the replies... .. i think ill just monitor my batteries the old way by seeing how much many mah's it takes to fully charge them after a few flights...and just check em under a load between flights
    \"Propellers are notorious for inflicting serious bodily harm while vigorously defending their space\" George Aldrich

  6. #6
    Minnreefer's Avatar
    Join Date
    Jan 2003
    Location
    Plymouth, MN
    Posts
    1,235
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please

    I have a question that deals with this thread, I hope you don't mind )), is there a product that measures amount of mah's one uses during a flight? I know more radios have telemetry built in and I would think that would be a handy feature to measure power draw. I know that you can get something like it for larger lipos.

    Thanks

    Jon
    Tiger 2 brotherhood #14
    The Common flyer, best of the lousiest, and lousiest of the best.

  7. #7
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,530
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please


    ORIGINAL: Minnreefer

    I have a question that deals with this thread, I hope you don't mind )), is there a product that measures amount of mah's one uses during a flight? I know more radios have telemetry built in and I would think that would be a handy feature to measure power draw. I know that you can get something like it for larger lipos.

    Thanks

    Jon
    Don't the Castle's ESC effectively do this automatically via their flight logging?

    The software produces a great chart showing instantaneous amp draw and averages. This can be used to easily calculate total draw if it doesn't do so already.

    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  8. #8

    Join Date
    May 2008
    Location
    Winnipeg, MB, CANADA
    Posts
    584
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please

    Just like lipos are at 50% at 3.85 volts life can be checked for capacity as well. What is required is a much better meter. Life do not have a flat discharge curve, yes they drop off very slowly but they do drop off and with a good meter they can be checked for capacity that way.

    I have no experience with the above meter but I have used a voltmagic for the past 4 years on A123 and it has been bang on regarding capacity left. It works just like a voltwatch on a NIXX battery and when I hit the yellow light I put back in the same amount each and every time so I know it works.

    http://www.voltmagic.com/
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Jh15537.jpg 
Views:	1 
Size:	150.9 KB 
ID:	1803099  

  9. #9

    Join Date
    May 2009
    Location
    Amelia, VA
    Posts
    1,960
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Explain this please


    ORIGINAL: MetallicaJunkie

    thanks for the replies... .. i think ill just monitor my batteries the old way by seeing how much many mah's it takes to fully charge them after a few flights...and just check em under a load between flights
    This will certainly work fine and save a few dollars to boot. I was very skeptical going in to A123 and now that I have them I am amazed that I don't need a voltmeter at all. It is a waste of extra dollars in this case. I just charge and fly initially, come back charge and see the usage. After that only charge to top off.

    As a matter of fact since switching to all A123s it seems to me that I have a far better grasp as to how my planes use the batteries than I ever did with a voltmeter. Voltmeter may show voltage, but we have to remember it does not show capacity. Now, I know exactly how many times I can fly and the super bonus is that you can charge them so fast it is amazing. Plug the charger up and in minutes you are charged and ready to get back in the air.

    I hardly ever pull out a voltmeter any more. The only time I use one is to check my NIMH ignition batteries and I really would not need to do that as I have developed a consistant pattern in how I use them. I know you can get used to using a voltmeter on A123, I just think it is additional time and cost that is no longer needed.


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
All times are GMT -6. The time now is 09:40 AM.

SEO by vBSEO 3.6.1 ©2011, Crawlability, Inc.