Battery C rate, and what it means

Discussion in 'Newb Guides' started by GJH105775, Apr 17, 2015.

  1. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    I have noticed that there is a lot of confusion as what the C rate of a battery actually is. So I decided to do this quick post.

    C rate is the discharge rate of the battery, or how much current it can supply.

    How do I get the Amp supply from the C rate? For this example we'll use this battery.
    If you have a 10C battery that means it can discharge 10 * the capacity. Remember that you usually measure current in amps and not milli-amps, so you convert the capacity (the battery we chose is 5200mah) so 5200mAh = 5.2Ah, and 10*5.2 = 52, so you can discharge 52 amps constant. if the battery has 20C burst then you can discharge 104 amps for ~10 seconds.


    Amp output = C * Ah (not mAh)

    so: the simple way to do this is A = C*(mAh/1000)





     
    Last edited: Apr 27, 2015
  2. holtneil

    holtneil Well-Known Member Moderator

    Hi George yes spot on as all your posts I will stick it
     
  3. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    Thanks for the sticky, so do you believe that this is the right place for this then?
     
  4. holtneil

    holtneil Well-Known Member Moderator

    Yeah It should be ok if not we can move it later on
     
  5. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    Sounds good.
     
  6. alm865

    alm865 Active Member

    Can I also add that:

    Higher C
    rating typically = Heavier battery (i.e. lower AWG (e.g. larger diameter) cables needed, heavier battery cells).
    Lower C rating typically = Lighter battery

    So generally going to a high C battery (i.e. 70C) is not always the best choice if your Quad only draws a peak of, lets say, 10C for example. Also lower C rating lipos tend to cost less.

    Reference Link(s) here.
     
  7. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator


    Ok, I'll quote your post, the density of the battery cells is the main factor to C rate, and this really affects weight.
     
  8. Yesha

    Yesha Member

    Hi, it's my first time building a quadcopter, and each of my electronic speed are 30 amps, and i need a battery that can support 120 amps in total, so the battery you mentioned, is it good for my quadcopter to maintain flight? and for how long can it stay in flight?
     
  9. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    Can you provide a link to the motors? It is unlikely that you need the full 30 amp cushion.
     
  10. Yesha

    Yesha Member

    http://www.hobbyking.com/hobbyking/...s_2_Motors_.html?strSearch=multistar elite 23

    These are the motors i'm using.

    http://www.hobbyking.com/hobbyking/...Heli_Multi_rotor_Brushless_ESC_2_6S_V2_0.html

    and these are the electronic speed controllers i'm using.

    I want to know what type of battery and how much mAh i will need to support these electronics and my quadcopter to take flight.
    My teacher said it probably won't use 30 amps completely, because i'm not racing it, it made to only hover and take flight. My teacher said probably 75% of amps will be used in the process. So since there are 4 ESCs and each are 30 amps, in total that's 120 amps, and 75% of that will be 90 amps. So i need a battery that can support 90 amps.
     
  11. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    You'll never pull the 30 amps on these motors without burning them up, but get those as they'd support about any motor upgrade you'd get for it, a Turnigy Multistar 5200mAh, 3S1P, 10C-20C.
     
  12. Yesha

    Yesha Member

  13. SpaKteL

    SpaKteL Member

    But isn't 5.2x10=52A too low?
    Those motors have Max 18A. So together there is 72 A. That battery is not20A short? I a newbie so i am probably mistaken.
     
  14. GJH105775

    GJH105775 Avid Linux User, and U.S. Air Force 1C6 Moderator

    Well over drawing will decrease the battery's lifespan, however usually you are never going to draw the motor's max of course that is depending on what you are doing with it. I'd suggest that you get a battery with more capacity or a higher discharge rate if you are above the threshold by much and will be drawing much (check prop test for your motors and approximate weight).
     
  15. hddrone

    hddrone Member

    Thanks for making it sticky so all other users will be able to get this information. This will help them out know about their battery.
     
  16. SlyBazzle

    SlyBazzle Member

    Having a hard time figuring out what battery/charger setup to get for an Arris x speed type B but If I'm understanding this... higher Mah will only add flight time if the battery isn't too heavy and the higher the C rating is the heavier the battery is but the flow of power is a lot better. So it sounds like I have to find the happy medium between mah and C rating for the copter to fly most efficiently. Is this something that people generally have to fool around with to figure out or is there some sort of equation for all of this?
     
  17. holtneil

    holtneil Well-Known Member Moderator

    Hi Mate yes you have to work out what you want more of, arco quad higher C rate , racing quads can use lower C rate as flights are short , filming higher MAH for longer flight time , Hobby king do multistar batteries just for multirotor low C rate high Mah anf light weight , or look at Zippy compact not bad weight but a small size battery so good for tight for room quads
     
    SlyBazzle likes this.

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