Safely discharging a Lithium Polymer battery (LiPo) for disposal?

Discussion in 'Batteries & Power' started by Steve Maller, May 25, 2014.

  1. Steve Maller

    Steve Maller UAV Grief Counselor

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    I’ve been looking for a definitive answer to the question of how to safely dispose of a Lithium Polymer battery (a “LiPo” as we call them) that’s no longer suitable for use. The “salt bath” method favored by some seems to have some problems, and according to this video, is actually not effective.

    The method described in this video utilizes a device called at Computerized Battery Analyzer. The actual one referenced in the video is discontinued, but its successor is available here: http://www.westmountainradio.com/product_info.php?products_id=cba4

    I’ve seen descriptions of similar methods, but they involve something like a light bulb, which doesn’t seem as precise when it comes to regulating the current and properly draining all the potential from the battery.

    Of note: I found a couple of these CBAs for sale on eBay for significantly less than they cost new. I bought one, and I will report back once I get it. I have a couple of LiPos that have issues (usually a cell that’s gone bad) and I’d prefer to dispose of them rather than keep them around for other purposes.

     
  2. Gary McCready

    Gary McCready Active Member

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    CBA.JPG CBA.JPG
    I have a West Mountain CBA, and like it for analyzing my Lipos. I was having problem with some of my Nano-techs and one Zippy. It was great having the data to backup the fact that these batteries would not hold voltage, so I trashed them. You can save graphs for later comparison too, so I test all my new batteries after the first charge.
    It does take a long time, 4-8 hrs, to totally discharge one battery. Then I just bag them and take them to Lowes, where they have a bin for rechargeable batteries. For testing I just take them down 2v, 16.5 to 14.5, takes about 1 to 1 1/2 hrs. There is an "add-on" 5X amplifier which will take the batteries down alot (5X) faster, but it was too expensive. Still trying to get my Electrical Engineer son to make me one...lol.
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Good question, Steve. I've never been able to find out the "official answer." All I have done is use the "resistance discharge" a 24v DC light bulb (automotive) as a dummy load and connected it up to the LiPo, placing the LiPo and the bulb out on a concrete pad far from anything flammable and take the battery down to 0 volts.

    I had read that the LiPo tends to heat up as the cell voltage passes down through about 2.0 volts.

    The salt water method seems to just substitute conductive water in place of a resistance. You can see the discharge is happening from the battery terminals -- and it looks like oxidation terminates the discharge before the cells hit zero volts. The gaseous emission from the LiPo could be quite toxic -- perhaps someone with a chemical engineering background could comment.

    The video seems to be quite persuasive that the resistive discharge is takes a LiPo down to inert.

    Andy.
     
  4. Gary McCready

    Gary McCready Active Member

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    Put a battery in salt water and you get Hydrogen gas and oxygen. I kinda thought this was not the greatest way to do it??
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Yeah....electrolysis, as I recall. Salt water has a pretty low resistance (like 0.2 ohms if I'm recalling correctly), but, as I mentioned, I think the oxidation (or the formation of the H and O2 bubbles at the terminals) might cause cause an apparently higher resistance -- because at 0.2 ohms, that should pull a lot of current (e.g. 84 Amps on a 4S). It certainly doesn't look like 84 Amps, but I don't remember what the videographer said the Lipo's voltage was.

    Andy.
     

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