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Battery ~ Voltage per cell at full charge

Discussion in 'General Discussion' started by Dave Pitman, Nov 17, 2013.

  1. Dave Pitman

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    I wonder if any of you check your voltage per cell with a voltage tester on the balance plug at full charge from the phantom charger?

    A full charged 3S is 12.6 volts, which is what I consistently get. But, the middle cell always seems to be high (4.21) and the last a little low (4.19). The experts say that you should never charge a cell higher than 4.2 so I thought I would see what you guys are getting for comparison.

    Thx, Dave
     
  2. SCADAMON

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    I test mine all the time +/- .1v is ok...
     
  3. PhantomFan

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    I get 4.19 in cell 1 of one of my batteries, and 4.21 in the other two. I don't sweat the difference, even though I've read that the cells should be as evenly matched as possible.

    PF
     
  4. Dave Pitman

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    Okay, thanks guys.
     
  5. Gizmo3000

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    I have two testers and my charger has an indicator.
    and seems they ALL show different levels!@# (tho I seldom see 4.2, usually it says 4.18 or 4.19)
     
  6. jumanoc

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    If want to get similar cell voltage, use a good balance charger, not only charger. Every battery should be balanced at least every 4-5 charge cycles. Use a voltage metter. It is not safe to use a battery with voltage difference >0.1 v between cells.
     
  7. Dave Pitman

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    I think the stock charger is a balance charger, albeit probably a cheap one.

    As stated ^^, my voltages are consistantly 4.2, 4.21, 4.19 with the Phantom charger.
     
  8. Jenniar

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    Wonderful! But I don't know what will happen.
     
  9. Dave Pitman

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    After about 15 cycles, I am now getting:

    12.6 v total 4.2/ 4.24/ 4.19
     
  10. PhantomFan

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    I balance charge EVERY time I charge my battery. That was the recommendation in that battery tutorial I posted. Takes no extra effort...might help with longevity, certainly won't hurt.

    PF
     
  11. Ots

    Ots

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    Balancing cell voltage should be done frequently with a balancer, not just when charging. High voltage differences between cells have been known to cause problems.

    All metering devices have an associated % error so don't hang on to that second decimal place too tightly unless you're using an expensive calibrated piece of equipment.
     
  12. Dave Pitman

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    If you are talking about utilizing the balance plug on the stock Phantom charger, then yes, I use it every charge. If you are talking about using something else, please elaborate.

    The cell checker I use is a cheapo HobbyKing. However, My cell figures are using the same checker every time, so I'm guessing that the divergence over time is factual, but could be wrong.
     
  13. The Editor

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    4.21v is fine (you will probably find it will drop to 4.20 anyway)

    The 'death' threshold for Lipo's is 4.25v per cell. They should never be charged above that which is why chargers will switch to constant voltage charge once each cell reaches about 4.16v (but that will vary by charger depending on the chargers algorithm).

    You will also probably find that due to charger display inaccuracies that the actual voltage of the cell is maybe 4.206 or 4.207 and the display has 'rounded' the figure to 4.21v
     
  14. Dave Pitman

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    Getting pretty close to the threshold then, even with a rounding error.

     
  15. Ots

    Ots

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    There are a number of stand-alone balancers available ranging from $25.00 to $50.00. some of the manufacturers are Common Sense and Astro Flight but there are others.

    I balance my packs after use and a cool down period and then again after they are charged. It's a good practice not only for safety but for the longevity of the pack. Just balancing while charging isn't usually sufficient, and you get to see this with a stand alone balancer. It's actually a good indicator of a pack's overall condition. Good packs seem to balance quickly and older packs that have had a lot of use and some abuse take a lot longer. Some take all night long!