[RC modeling] li-Po battery advice sought..... | FerrariChat

[RC modeling] li-Po battery advice sought.....

Discussion in 'Aviation Chat' started by Fast_ian, Jan 26, 2015.

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  1. Fast_ian

    Fast_ian Two Time F1 World Champ

    Sep 25, 2006
    23,397
    Campbell, CA
    Full Name:
    Ian Anderson
    #1 Fast_ian, Jan 26, 2015
    Hey,

    A little OT I guess, but I know I've seen threads about modeling here before, so hopefully I'm OK.....

    I'm learning to fly a quad copter right now. Everything is progressing well, thanks for asking! ;)

    Pretty much my first experience with Li-Po batteries. I bought a 'real' charger that will do bigger packs when the time comes as the supplied USB thing was really slow.

    Surfing around tells me I should charge at no more than 1C. These are 1S, 500mah packs. I get about 10mins from each, and they're a little warm when I'm done. Very good....

    Set the charger to 0.5A. It does a good job - Eventually! Brings it up to 4.2v and the current drops off prior to auto shutoff. All good.....

    Except, there's zero increase in the pack temperature while charging.... This suggests to me that I could crank up the current some? I don't want any 787 'melt down' behavior (;)), but am tempted to go to, say, 1A on the charger...... Am I silly, or just conservative?....

    Any comments much appreciated, and again apologies for the somewhat OT nature of the post.

    Cheers,
    Ian
     
  2. Nurburgringer

    Nurburgringer F1 World Champ

    Jan 3, 2009
    11,032
    Texass
    #2 Nurburgringer, Jan 26, 2015
    Last edited: Jan 26, 2015
    Assume the battery doesn't have a label telling you the max charging rate?
    I've got some that say 3C, some 5C but these are bigger 3 or 4 cell packs.

    I've also seen a lipo fire firsthand in my garage (no idea why it happened, wasn't charging them very aggressively) so tend to err on the conservative/slow charging side now :/

    That being said, a 500maH 1cell battery is a tiny little thing. Set the charger and battery on a concrete floor a couple feet from anything and give it a go at 1A.

    I'm using two 3300mAh 60C 4 cell packs in my ME-262, which pulls around 120Amps/2000watts at WOT. Takes ~1 hr to parallel charge 4 of these packs at ~3A from ~3.75V to 4.2.

    Edit: here's some reading material on charging LiPos that may help:
    http://z8rc.com/turnigy-4x6s-400w-lipo-charger-4-x-100w/
     
  3. Fast_ian

    Fast_ian Two Time F1 World Champ

    Sep 25, 2006
    23,397
    Campbell, CA
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    Ian Anderson
    #3 Fast_ian, Jan 26, 2015
    I *love* this place!.... Get answers fast....

    Correct on the first part. These are definitely 'single cells' - Hence the '1C' designation. Labeled at 500maH and 1.9Wh. I believe 3C is 3 cells, 5C is 5 and so on - multiply the nominal 3.7v by the C number to get the desired charge voltage. (I think.....)

    Big boy stuff! :)

    Yeah, I'm thinking give it a (closely monitored ;)) 1A charge and keep feeling it for any 'alarming' temperature increases.

    Thanks for the comments,
    Cheers,
    Ian
     
  4. Nurburgringer

    Nurburgringer F1 World Champ

    Jan 3, 2009
    11,032
    Texass
    #4 Nurburgringer, Jan 26, 2015
    Last edited: Jan 26, 2015
    Ian -
    3C does not mean 3 cells.
    Shorthand for # of cells is 'S' i.e. 1S for one cell (4.2V fully charged) 2S (8.4V) etcetc

    You'll always be charging at 4.2V per cell, it's the amperage you can change.

    'C' represents capacity, or how many amps can be safely discharge (or charge)
    https://www.commonsenserc.com/page.php?page=c_ratings_explained.html
    EDIT: to clarify, a battery with a "10C" rating indicates the supposedly safe DISCHARGE rate.
    The safe CHARGE rate, if not explicitly stated somewhere else on the label, is normally 1C. One C.

    Examples: So a 10C 500mAh (0.5Ah) battery should be able to safely discharge at 5A.
    A 20C 1000mAh battery would safely discharge at 20Amps.
    Multiply C rating by the battery Amp-Hours to get the safe discharge.
    If your motor/prop exceed the true C rating (or you charge it too fast) the battery will get hot and "puff", and it will do some amount of damage to the battery's life. How much damage depends on how long and how much you exceeded it's capacity, quality of the battery, position of the moon etc.

    Like you were doing, most people recommend charging at no more than 1C i.e. 0.5Ah battery x 1C = 0.5A

    Post a pic of the label(s) on your battery, I'll see if I notice anything on it.

    PS: I'm a mechanical engineer, so getting this electrical black magic **** right takes effort too :p
     
  5. Fast_ian

    Fast_ian Two Time F1 World Champ

    Sep 25, 2006
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    Ian Anderson
    #5 Fast_ian, Jan 26, 2015
    Last edited by a moderator: Sep 7, 2017
    Indeed....Sorry, got my 'S' & 'C's bass ackwards there.... Actually realized my screw up after I posted and looked at the charger; "6S balancing charger".....

    ;)

    Yep, these are *tiny* little batteries. I just 'associate' some heat with a nice charging cycle.... Makes me feel like they're working.... ;)

    Cheers,
    Ian

    Here we go;
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  6. Fast_ian

    Fast_ian Two Time F1 World Champ

    Sep 25, 2006
    23,397
    Campbell, CA
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    Ian Anderson
    #6 Fast_ian, Jan 26, 2015
    Darn it!.... Upside down.... :( ;)
     

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