Properly discharging and storing LiPo batteries.

Discussion in 'MōVI M10' started by Clarke Mayer, May 11, 2014.

  1. Clarke Mayer

    Clarke Mayer New Member

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    Hello all,

    I'm impressed with the speed and accuracy of response time on this forum. Thanks to both Freefly Systems and the MoVI community. I think I'm pretty solid on the LiPo battery education thus far, just still new to it. A couple more questions if someone wouldn't mind. After recommendations to buy LiPo sacks for proper battery charging, I picked a few up yesterday at my local hobby shop. I also bought a voltage checker to check the cells of each battery and put some Velcro on that sucker and paired it with the stand so I always have it. I am a bit of a perfectionist though, and I just wanted to make sure I was doing the process right. My voltage checker checks each cell one by one, then gives an overall reading. I'm cool with that. I just wanted to confirm some logistics.

    1. The MoVI M5 manual states that the batteries should be stored around 3.8V/Cell when not in use for a while (I mean seriously though, who isn't using their MoVI LIKE EVERY DAY? :) ) Am I correct about this?

    2. If a battery is full, how do you discharge it to store it? I have heard people have just been running them in their equipment until the battery is at a convenient charging spot.

    3. Is there any talk of Freefly updating their firmware to give cell read outs in the software directly?

    4. Once the battery is at a safe storage spot, where do people keep them for safe storage in their LiPo sacks? A garage, a basement? I assume anything with a cement floor would be ideal, away from other objects.

    5. I understand that people have been running the batteries until the MoVI itself shuts down and then charging them, using the MoVI's internal regulator to know when the battery is dead. As an alternative, where might that be in terms of Voltage as a whole/per cell. For example, if the battery shouldn't go below 3.0V/Cell, is 3.2V/Cell or 3.3V/Cell a good indicator to take the battery out and charge it? I only ask because considering the specific attention required for these batteries, it would be nice to get a more accurate answer then, "The MoVI will shut down and that is a good indicator." So, when on the voltage scale have people been pulling their batteries before they reach 3.0V/Cell?

    Help is greatly appreciated. Thanks.

    Clarke Mayer
    www.clarkemayer.com
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    With LiPos you need to be. There are many phrases about abusing Lipos on the Internet and they almost always end with either:
    1. The LiPo won't charge up.
    2. The LiPo doesn't deliver full capacity.
    3. There is a risk that the LiPo will catch fire.

    And bear in mind a Lipo fire cannot be extinguished except with a Class D extinguisher -- it provides it's own oxygen so has to be smothered.

    Yes. By picking the mid-point voltage between 4.2 and 3.3, which is close enough to 3.8V/cell, the battery will last longer -- or so the conventional wisdom holds. I'm not sure who (if anyone) has really done the physics to prove this, but enough people have found out the consequences of holding the LiPo fully charged, or over-discharging them. (See my points 1. and 2.).

    Some higher end chargers have a "Store" function that deliberately raise or lowers the cell voltage to 3.8. Otherwise, you can either (a) connect it to a MōVI and let it run down or (b) rig up a harness using a car light bulb as a dummy load and discharge the LiPo to 15 volts (total).

    You just started that rumor. :)
    The three green LEDs give you an approximation to the total voltage and thus you can infer the per cell voltage.

    Anywhere you feel safe having a LiPo catch fire. Personally, I use an ammo box from Fisherman's Marine. I drill at 10mm vent hole in the lid (it's very soft metal), and then put PVC tape over the inside and outside of the hole. This acts a pressure relief valve in the event of a fire as otherwise the ammo box is gas tight. Bad Idea.

    Personally, I swap the LiPo out when there is only one LED on -- but depending on what's going on on the set, I'll often choose to swap out when there are two LEDs.

     
    Dominic Eder-Smigura likes this.
  3. Clarke Mayer

    Clarke Mayer New Member

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    Andy,

    You rock. Thanks.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Glad the info helps.
    Your questions are all valid ones and I had struggle to find answers to, too.

    Andy.
     
  5. Sudhava Ramesh

    Sudhava Ramesh New Member

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    This is useful. Thanks :)
     

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