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Thread: Charging LiPo question.

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  1. Charging LiPo question. 
    #1
    Join Date
    01-26-2002
    Location
    ON, Canada
    Posts
    1,645
    Hi Guys...I have some questions.

    I just started balancing and charging LiPo for the first time. Equipment: LiPo is SMC 2S 5200mah; charger is ICE; Balancer is Equinox and I have a 2/3s LiPo cell reader. On my first LiPo. I have it charged at 1C and 100% max capacity charge. Let the charger do it's thing until it finished charging (CC-CV cut-off). To my surprise, it only took 4820mah. Is this normal? Checked with my balancer and it is showing the 2 cells are balanced (reading 1 - 4.2; 2 - 4.19). Is it because each cell reached 4.2v already, that is why it cut off? Will it hold more charge as time goes by? I'll be charging my 2nd LiPo tomorrow and I will check if it will do the same.

    Why does ICE have a setting of 110 to 120 % max charge on LiPo? Isn't that dangerous? Let us say that my LiPo does reach 5200mah and since it is on 120% charge capacity, it will continue accept charge 'till it reach 5824mah? Does any charge that goes inside the LiPo higher than the stated capacity bad for the battery? I have NiMh and they do go beyond their rated capacity and they feel very warm. I don't have experience yet with LiPo.

    Please enlighten me. Thank you guys.
     

  2.  
    #2
    Join Date
    08-19-2002
    Location
    Wichita, ks
    Posts
    10,365
    You shouldn't really discharge a lipo more than about 80% of its full capacity, and if your low voltage cutoff is set properly, you shouldn't pull out more than about 4600-4800mAh. Running any more is just hard on the pack.

    Your MAXIMUM voltage per cell is 4.20v. Some chargers can/will charge to 4.25 or 4.30v/cell but is generally not a good idea. I don't think the ICE has this feature anyway. CC-CV means that it charges at a "Constant Current" until it hits 4.20v/cell. Then, it switches to a "Constant Voltage" mode which basically turns your charger into an 8.4v power supply (on a 2s pack) that will hold the battery at that voltage until 0A of current are required to hold the voltage. That's why the last 10% or so of the charge takes longer than the rest of it.

    The 110-120% max charge is most likely just a capacity rating. My SMC 4100 actually took about 4300 if I remember right after the first time I ran it to my 6.5V low voltage cutoff, which is very abnormal for a LiPo pack. A LiPo charger that will only allow 100% would cause it to shut off early.

    NiMH packs going over their rated capacity while charging doesn't mean anything. If you discharge them at 10A, I'll bet they hold considerably less than their rated capacity if they're cheaper packs.

    LiPo packs should NEVER get warm while charging. If they do, something has gone horribly wrong.

    Are you using High Power charge leads with your Equinox balancer? You really need to if you're charging faster than about 3.0A if I remember right.

    Does this help? Any clarification required just ask.

    -Eric
     

  3.  
    #3
    Join Date
    11-09-2002
    Location
    San Jose, CA
    Posts
    1,014
    I got a stupid question. I want to balance some of my lipos but not sure what charge rate to charge them at? My Hyperion charger doesn't really state a recommended rate and just kinds of charges it at whatever rate I set it to. So thats why I have not really done balancing charging.

    I typically charge my lipos at 1C rate. Any idea guys?
     

  4.  
    #4
    Join Date
    02-20-2002
    Posts
    3,695
    !c is a good rule of thumb and is many times considered the safe maximum. You can still use that rate while balancing.
     

  5.  
    #5
    Join Date
    07-04-2006
    Posts
    1,744
    Lipo completely different from NiMh's. Read alittle bit of charging lipo. NiMh can be charged 25% of its capacity. Which make them heat up in temp.

    Lipo's max of 4.3v per cell, max amp 1.0v per cell. When charging temp will not be over room temp. If they are warm, overcharging has occured and be disconnected.

    NiMh'scan discharged to 0v but better at .9-1v cut-off. Lipo's 3v cut-off, never less than 3v. Good ESC 3.5v cut-off is my liking. Less then 3v cutoff destroys the lifetime of lipo.

    Good lipo chargers are ones that charge aircraft lipo's. They charge at 1amp, voltage start at 4.3v then drops to 0v. Never temp over room temp...
    If 5200 mah lipo on charger will never reach 5200mah, may be 4800mah. Cuz, You never discharge lipo completely, recharge them at 3v residual, or when the the good charger cut itself off. Most lipo chargers turns off, you don't need to trickle charge lipo's.

    Most aircraft charger are better than the ICE battery charger. The automatically set itself through 2 -6 cell lipo and for voltage with 1 amp max.

    Safety during charging, they should be babysat and watch for temp monitored. Never leave them alone.

    Read maintenance of lipo in MaxAmps web or look up in google. Learning about lipo's is easy, and understandin of knowledge of lipo's is greatly needed, it'll be safer in what to and what not to do.

    Good luck and have fun.
     

  6.  
    #6
    Join Date
    01-26-2002
    Location
    ON, Canada
    Posts
    1,645
    FULL OF INFORMATION GUYS. THANK YOU!

    My questions have been answered. Before, I am so scared about LiPo. Now, with the right knowledge. Correct equipment. Safe handling and charging...it is the best thing next to sliced bread (RC related anyways ).

    I don't take them for granted too. Always present when being charged or balanced. Inside a LiPo sack and cash box. Charge them at 1C and with temp. sensor attached.

    I just ran my Savage Flux and I can't believe the juice LiPo gives. More than 2- 7cells 4600 nimh.

    RCcardude. I just have the ordinary Equinox attachment. You are right in buying the optional hi-rate attachment if I want to use it as a charge-through-balancer. I use it for now as a stand alone balancer. I have the 2/3S digital reader to check if the readings are very near to each other.

    Again, Thanks guys!
     

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