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  1. #1
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    What causes LiPos to puff?

    I assume my batteries are dead, but I'm curious as to what causes LiPos to puff, and how to avoid it.

  2. #2
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    wrong specs for the job. (Too small or on lower limits of Amp discharge)
    Handling/physical mistreatment. (dropping, getting knocked about in chassis)
    Not using a reliable charger. (Budget chargers.)
    Hitting the LVC every time it's used. (Packs don't like going too low, even if it is within the safe low voltage range)
    Age and cycles on pack. (batteries don't last for ever).
    Budget packs (some budget packs are great, some aint).
    They puff because of stress. Puffing is ok, as long as you know the difference between a pack thats puffed and a pack that has swolling.
    Guide books aren't part of the packaging.

  3. #3
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    I use 6S lipos in my Spartan and I run them to LVD and then discharge them to 9 volts to get a better charge. Is this bad for them to do this?



    E-Maxx and Spartan

  4. #4
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Yes, extremely.
    6S minimum voltage is 18 volts. By discharging them down to 9 you are damaging the pack.

    Also, there is absolutely no reason to discharge LiPo's to get a "better" charge. LiPo has no memory what so ever.
    Whatever it is I just typed... could be wrong.

  5. #5
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    I wouldn't, Check the temps of the lipos after the run doing this. They will most probably increase in a short time.
    Guide books aren't part of the packaging.

  6. #6
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    Radical change in temp/pressure will also cause them to puff.

    I accidentally let mine get shipped in a non-temperature contolled moving truck across country in the middle of June and a few puffed up.

  7. #7
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    Quote Originally Posted by PowerDemon View Post
    I use 6S lipos in my Spartan and I run them to LVD and then discharge them to 9 volts to get a better charge. Is this bad for them to do this?



    E-Maxx and Spartan
    9v on a 3s is "ok" (3v per cell) but in one pack of 6s is BAD, is like ~0.6v per cell
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  8. #8
    RC Turnbuckle Jr. 87 GN's Avatar
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    Quote Originally Posted by PowerDemon View Post
    I use 6S lipos in my Spartan and I run them to LVD and then discharge them to 9 volts to get a better charge. Is this bad for them to do this?



    E-Maxx and Spartan
    I read that correctly, you are discharging them to 3.0 volts per cell.. You should never run a lipo below 3.4v per cell, shorten the life of the battery.......
    & store them at 3.85v
    Would you go flip my truck back over??

  9. #9
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    Quote Originally Posted by 87 GN View Post
    I read that correctly, you are discharging them to 3.0 volts per cell.. You should never run a lipo below 3.4v per cell, shorten the life of the battery.......
    & store them at 3.85v
    2.75v per cel is the absolute minimun but is VERY dangerous, 3v per cell is the recomended minimun for lipos in general
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  10. #10
    RC Turnbuckle Jr.
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    Quote Originally Posted by DBG View Post
    2.75v per cel is the absolute minimun but is VERY dangerous, 3v per cell is the recomended minimun for lipos in general
    Those are the old school numbers that testing by an Engineer has proven to be far to low.

  11. #11
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    Quote Originally Posted by Jakey View Post
    Those are the old school numbers that testing by an Engineer has proven to be far to low.
    Those numbers are proved by the manufacturer after a lot of researching (from the low quality Chinese cell to the high quality German cells) 3.4v per cell is for be safe because under high loads, the battery can get way to low and 3v is dangerous BUT in a constant, low amp discharging, is safe
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  12. #12
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    deep discharge.

  13. #13
    RC Turnbuckle Jr.
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    Quote Originally Posted by DBG View Post
    Those numbers are proved by the manufacturer after a lot of researching (from the low quality Chinese cell to the high quality German cells) 3.4v per cell is for be safe because under high loads, the battery can get way to low and 3v is dangerous BUT in a constant, low amp discharging, is safe
    I am going to be frank here - I have tested more RC LiPo packs than most people can comprehend. These tested packs include those from low quality/low cost factories, ranging up to some of the very best performing RC batteries currently available today. And I can say with complete confidence, for our typical RC use a cutoff of 3.0 volts per cell is too low. So please stop recommending operating parameters that been proven to be harmful to RC LiPo packs.

  14. #14
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    Quote Originally Posted by Jakey View Post
    I am going to be frank here - I have tested more RC LiPo packs than most people can comprehend. These tested packs include those from low quality/low cost factories, ranging up to some of the very best performing RC batteries currently available today. And I can say with complete confidence, for our typical RC use a cutoff of 3.0 volts per cell is too low. So please stop recommending operating parameters that been proven to be harmful to RC LiPo packs.
    I am assuming the 3v per cell is safe because of this:

    Quote Originally Posted by PowerDemon View Post
    I use 6S lipos in my Spartan and I run them to LVD and then discharge them to 9 volts to get a better charge. Is this bad for them to do this?



    E-Maxx and Spartan
    I am assuming he is discharging a pair of 3s batteries with a charger with discharger function using low current...I am not saying go discharge a LiPo at 100c to 3v per cell using you car or boat, please read before post.
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  15. #15
    Marshal Dadx2mj's Avatar
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    ^^^^ Those are some dangerous assumptions.

    Check with the battery manufacturer as to how low their cells can safely be discharged if you have doubt. I personally set my LVC to 3.6v as the extra minute of run time with a lower setting is just not worth shortening the lifespan of the battery.
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  16. #16
    Marshal ksb51rl's Avatar
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    Quote Originally Posted by DBG View Post
    I am assuming the 3v per cell is safe because of this:


    I am assuming he is discharging a pair of 3s batteries with a charger with discharger function using low current...I am not saying go discharge a LiPo at 100c to 3v per cell using you car or boat, please read before post.
    I read it...and you're still wrong. Depth of Discharge is a function of voltage, not of . There is a reason for the now-common recommendation for DoD to be in the 80 percentiles: because packs become damaged and fail when run down to literally nothing. There is no reason to run down to 3.0v/cell. It doesn't promote the lifespan or usable power of the pack. In fact it does the opposite. In your scenario, the reduced amp draw will delay the triggering of Low Voltage Cutoff/Detection. This will increase the DoD and decrease the useful life and the performance of your LiPo packs.

    To get maximum cycle life out of your packs you should set the cut off on the high side. Cycle life is greatly increased if a cell/pack isn't discharged below 80% of its capacity. This is referred as Depth of Discharge (DOD). Unfortunately the speed control manufacturers didn't take this into account when designing there systems to be used with LiPo packs. If your speed control is set at 3V or 3.2V per cell which seems to be the common voltage used as default in most speed controls this will result in 99% and 98% DOD. By increasing the cut off to 3.4V per cell the DOD will be 96%. If 3.6V is used this will result in 85% DOD. These calculations are provided by info gathered on testing equipment which is calibrated to compensate for voltage drop. The DOD will fluctuate based on a cell/packs resistance and the discharge load being pulled from the cell/pack. A motor which pulls less amps will discharge a pack more as there will be less voltage drop. It's up to you to determine if you want maximum play time or maximum cycle life. The info above is intended to help you make this decision.
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