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Odd Times For Storage Charge

Discussion in 'Phantom 1 Discussion' started by PTCX, Jul 9, 2015.

  1. PTCX

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    I have recently bought two Turnagy Multistar 4000mAh batteries and today after a flight session I used the storage charge function on my Spider charger on these batteries for the first time and the first one took only 2 minutes to reach the storage charge level,according to the charger,and the second was there as soon as I activated the charger.
    The 2700mAh batteries I have take around an hour to get to the storage level and that seems normal.
    I was expecting the 4000mAh batteries to take longer to reach storage level or at least as long as the 2700mAh batts.

    All the batteries after storage charge are showing 11.38 to 11.39 volts and one of the 4000mAh batteries is showing 11.43 volts.

    They where all flown to the first sign of red led on hard acceleration then landed.

    The 4000's have only been used/cycled four times and the 2700's are 5-6 months old,lost count of how many times they have been cycled.Still getting good flight times and no puffyness.

    So is it just coincidental and the 4000mAh batts were at the right storage voltage or should I be concered about them?

    By the by,I would not buy the 4000's again as they have only given up to 2 minutes more flight time on the first two flights each and now they are on par with the 2700's at around 8 minutes on a calm day.
    I think my Phantom is at a weight where the extra flight time potential is cancelled out by the extra weight.
    I'm thinking of trying the Multistar 3000mAh next.

    I'll keep the 4000's for a hex I will be building up over the next few months.
     
  2. Ti22

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    Sorry, dunno your Spider charger but if it’s anything like the iCharger your results do seem odd but perhaps there’s other things at work. Do you connect balance connectors and does your charger show balance channel voltages?

    If so (or if you can manually measure them) are they all around 3.8V?

    This storage voltage business is sorta “black art/science”. Many experts do recommend 3.85V/cell storage voltage which is industry standard. My experience with using large volumes RC Lipo packs/bricks over 7 years is you’ll see significant benefits long-term storing at least under 4V/cell. Yeah, 3.85V is “better” but not by very much IME. Main thing for long-term is to just keep them under 4V/cell in cool, dry location.

    And if I know I’m using them the next day, I don’t bother with storage voltages either and charge after use and be ready to go. But if it’s gonna be more than 24h it’s best to burn some charge off.

    OP - if you really wanna get to the bottom of battery performance you’ll need to work out some capacity and IR (internal resistance) measurement setup and metering. It doesn’t need to be “lab grade” but you can tell a LOT about battery pack health and performance by performing a few relatively simple qualification tests.

    Anybody with a DVM and soldering iron can whip something up with a few scrap/surplus appliances such as electric heater elements, etc. Some basic workshop tools, wire and connectors you can better understand an EXTREMELY important technology to our endeavors.
     
  3. PTCX

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    The charger is a Redback Racing Spider S1.
    Ballance charger/discharger , fast charger . Preset storage charge . Internal resistance testing etc.
    Yes I connect balance leads.
    Charger shows balance channel voltages.

    Below measurements are in current storage charge state.

    The 4000mAh are #1= 3.80v , 3.79v , 3.80v & IR is 23m/ohm 009 007 007 m/ohm
    #2= 3.79v , 3.80v , 3.81v & IR is 18 m/ohm 009 003 006 m/ohm

    The 2700mAh batteries.
    #1= 3.78v , 3.80v , 3.80v & IR is 19m/ohm 009 003 007 m/ohm
    #2= 3.80 on all cells & IR is 21m/ohm 009 005 007 m/ohm
    #3= 3.70v , 3.80v , 3.80v & IR is 21m/ohm 009 005 007 m/ohm

    Make of that what you will.

    Here's a thought,could it be the discharge rate making the difference?
    The 2700's are 25C and the 4000's are 10C.
     
    #3 PTCX, Jul 9, 2015
    Last edited: Jul 9, 2015
  4. Ti22

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    If accurate, those IR measurements look decent. 9mOhm on that same channel across all the bricks makes me wonder if there might be possible issue with the charger? I usually get better data doing manual IR test - record resting voltage, apply known Amp load for about 10s, record loaded voltage and do the math. By around 15mOhm you’ll definitely start to notice some degradation and more voltage sag.

    But, nothing seems to be that out of whack here. Maybe the difference in reaching storage charge had to do with the direction the packs needed to go? It’s often much slower to discharge than to charge so if one pack needed to be discharged much more than the other, I could see a major time difference.