Andy48 Posted March 12, 2017 Share Posted March 12, 2017 I had a batch of old lipos to recycle and used my usual method for discharging fully, a 12v car bulb. I then checked all the voltages were at zero, which they were. Out of curiosity I then checked the individual cells at the balance lead, and found that while every battery had at least one cell at zero, many other cells were as high as 3.8v. Clearly the light bulb discharge method really doesn't work. I then left them in a strong salt water bath for a week until all the fizzing had stopped. You must leave them outside as the gas given off is hydrogen plus heaven knows what. As can be seen from the photo this produced a lot of gunge. The blue stuff is copper sulphate, the white stuff has come out of the various cell pouches where the pouch had split or not sealed properly. After this treatment, all the cells were at zero volts. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted March 12, 2017 Share Posted March 12, 2017 Andy please note the BMFA no longer advise the use of soaking in salt water as it can leach lithium into the water which then enters the water system - the guidance document is here **LINK** Quote Link to comment Share on other sites More sharing options...
Andy48 Posted March 12, 2017 Author Share Posted March 12, 2017 The method for discharge used by BMFA however is clearly flawed and does not discharge each cell, unless one connects a resistor to each cell in the battery through the balance port. Using litium to trace leaks in water mains Hmmm! It has actually been proposed to introduce lithium into water supplies to reduce the suicide rates! **LINK** This adds a different perspective to the BMFA guidance. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted March 12, 2017 Share Posted March 12, 2017 Non the less its against BMFA recommended best practices - by all means ignore them on a personal level but "advertising" the discredited method as the best way is in my view not the way to go Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted March 12, 2017 Share Posted March 12, 2017 So going back one stage, what is your criteria that the lipo has reached the end of its life? Cell voltage? Discharge/charge capacity compared with original rating? and what value? Gone puffy and stays that way Reduction in its C rating (lost its punch? Quote Link to comment Share on other sites More sharing options...
John Emms 1 Posted March 12, 2017 Share Posted March 12, 2017 The correct method has always been to reduce the cells to near zero using a bulb or other suitable resistance. I always stored packs that have been given to us for disposal in the garden. Missing from the BMFA guidance is that if similar packs are to be combined in parallel, all pairs of cells through the packs must be linked to each other, and not simply the positive and negative leads of the packs joined together. Hope that helps, John Quote Link to comment Share on other sites More sharing options...
MattyB Posted March 12, 2017 Share Posted March 12, 2017 Posted by Andy48 on 12/03/2017 20:22:58: I had a batch of old lipos to recycle and used my usual method for discharging fully, a 12v car bulb. I then checked all the voltages were at zero, which they were. Out of curiosity I then checked the individual cells at the balance lead, and found that while every battery had at least one cell at zero, many other cells were as high as 3.8v. So let me check my understanding... you were discharging these packs individually one after the other using a 12V bulb connected across the main power connector? Very strange... I have done that whenever I've been disposing of a battery and have never had any issue getting all cells down to 0.1-0.2V, by which point there is essentially zero energy left in the pack anyway. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 12, 2017 Share Posted March 12, 2017 Posted by Chris Walby on 12/03/2017 21:09:57: So going back one stage, what is your criteria that the lipo has reached the end of its life? Some might consider a pack so puffed that the cell seams are starting to un-crimp as rather near end of life......mightn't they, Chris! Some of Andy's cells seem to have gone open circuit during the discharge if the pack voltages have dropped to zero with cells which are still significantly charged. I can't say that I can recall checking the individual cells on deliberately discharged packs...perhaps this is fairly common? Chris might be in a position to run one or two practical experiments...? Quote Link to comment Share on other sites More sharing options...
gangster Posted March 13, 2017 Share Posted March 13, 2017 Surely if the pack has been discharged with the bulb it can have very little ooomph left in regardless of what the vo ltmeter says for an individual cell. Hand wringers get ready, I still love the garden fork method of discharge. Yes I know...... but I am a kid of the 60s and most of us survived childhood despite! Quote Link to comment Share on other sites More sharing options...
Don Fry Posted March 13, 2017 Share Posted March 13, 2017 I always thought that local authority battery bins, and the recycling systems following behind do not care if the packs are discharged or not. Anyone have any knowledge? Quote Link to comment Share on other sites More sharing options...
PeterF Posted March 13, 2017 Share Posted March 13, 2017 Posted by gangster on 13/03/2017 07:16:47: Surely if the pack has been discharged with the bulb it can have very little ooomph left in regardless of what the vo ltmeter says for an individual cell. No, if one cell fails or a cell to cell solder connection break during discharge, the voltmeter may read zero volts over the whole pack because the pack has a break in the circuit, but all of the cells could still be charged to some extent. Quote Link to comment Share on other sites More sharing options...
Wihtgar Posted March 13, 2017 Share Posted March 13, 2017 I always use a 12V car bulb to discharge each cell via the balance lead by soldering insulated wires onto the bulb which fit into the balance connector making sure they cannot make contact with each other. I do this after discharging the pack in the charger, then the whole pack using the bulb, assuming that there are no open circuits in the pack. I wait a day or so and repeat the discharge process as the cells seem to recover slightly I then take them to the local recycling centre in an old jiffy bag marked up as discharged LIPO cells. The recycling people don't seem to be aware of their potential dangers which is why they should be discharged before disposal. Quote Link to comment Share on other sites More sharing options...
gangster Posted March 13, 2017 Share Posted March 13, 2017 PeterF. I understand your point and it would be a definite possibility if the reason for scrapping was total failure. But if you were discharging a pack for the many reasons quoted it would be highly improbable that an internal joint would fail partway through a discharge of a fraction of its normal working current. It's final minutes of its working life Likewise unless the cells at zero were already dead they would all show a few volts if it broke down partway through Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 13, 2017 Share Posted March 13, 2017 Posted by gangster on 13/03/2017 07:16:47: Hand wringers get ready, I still love the garden fork method of discharge. Yes I know...... but I am a kid of the 60s and most of us survived childhood despite! Fun, isn't it! I seem to recall indulging in pyromania with anything that could explode or burn spectacularly during those long sixties summer days. One or two of us ended up with minor burns but it was all part of the learning process. But not to be recommended in these litigious and safety obsessed days of course... Edited By Martin Harris on 13/03/2017 10:00:49 Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted March 13, 2017 Share Posted March 13, 2017 save all the hassle and hand them in to the local recycling depot(martins is a good way also)..... but the times we live in........... ken Anderson...ne...1...... sparks dept. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 13, 2017 Share Posted March 13, 2017 Posted by gangster on 13/03/2017 09:37:30: PeterF. I understand your point and it would be a definite possibility if the reason for scrapping was total failure. But if you were discharging a pack for the many reasons quoted it would be highly improbable that an internal joint would fail partway through a discharge of a fraction of its normal working current. It's final minutes of its working life Likewise unless the cells at zero were already dead they would all show a few volts if it broke down partway through More likely that some of the cells have broken down when going significantly below 3v - while there are instances of recovering fully discharged batteries, these were probably fairly new and well balanced - old cells with varying IRs may behave rather differently. Quote Link to comment Share on other sites More sharing options...
GONZO Posted March 13, 2017 Share Posted March 13, 2017 Donald, I've told this before, but one more time will not hurt. When I contacted my local council recycling office re LiPo disposal the lady on the phone told me to just put them in the 'battery bag' provided and give them to the truck. When ask about discharging and other actions she got quite agitated and officious, "just put them in the bag!". So I do nothing and just throw them away in the 'battery bag' and have done for some years. I'm still waiting to read about any fires on recycling trucks. Quote Link to comment Share on other sites More sharing options...
Andy48 Posted March 13, 2017 Author Share Posted March 13, 2017 Posted by MattyB on 12/03/2017 21:56:41: So let me check my understanding... you were discharging these packs individually one after the other using a 12V bulb connected across the main power connector? Very strange... I have done that whenever I've been disposing of a battery and have never had any issue getting all cells down to 0.1-0.2V, by which point there is essentially zero energy left in the pack anyway. Did you actually check the voltage of each cell? I generally find out a battery is going using the FrSky voltage sensing telemetry, where it warns of the lowest individual cell voltage. I get the warning usually on full power, with a battery that should be at least half charged. When it happens with a fully charged battery I know it is time to dispose of the battery. Why do all the cells not discharge at the same time? Probably because one cell holds far less charge than the rest and as it discharges the IR rises in that cell and prevents the other cells discharging. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted March 13, 2017 Share Posted March 13, 2017 So when is it disposal time, excluding damage and cell failure being the catalyst? That puffy it looks more like a sausage...but holds its capacity to 95% of rating and can give its all at its C rating? Quote Link to comment Share on other sites More sharing options...
Dickw Posted March 13, 2017 Share Posted March 13, 2017 Posted by Andy48 on 13/03/2017 11:50:17: Posted by MattyB on 12/03/2017 21:56:41: So let me check my understanding... you were discharging these packs individually one after the other using a 12V bulb connected across the main power connector? Very strange... I have done that whenever I've been disposing of a battery and have never had any issue getting all cells down to 0.1-0.2V, by which point there is essentially zero energy left in the pack anyway. Did you actually check the voltage of each cell? I generally find out a battery is going using the FrSky voltage sensing telemetry, where it warns of the lowest individual cell voltage. I get the warning usually on full power, with a battery that should be at least half charged. When it happens with a fully charged battery I know it is time to dispose of the battery. Why do all the cells not discharge at the same time? Probably because one cell holds far less charge than the rest and as it discharges the IR rises in that cell and prevents the other cells discharging. Like Matty I discharge packs with a bulb and have never failed to have them discharge completeley - and yes I do check individual cell voltages. Just think how far IR would have to rise to prevent the other cells discharging. Dick Quote Link to comment Share on other sites More sharing options...
MattyB Posted March 13, 2017 Share Posted March 13, 2017 Posted by Andy48 on 13/03/2017 11:50:17: Posted by MattyB on 12/03/2017 21:56:41: So let me check my understanding... you were discharging these packs individually one after the other using a 12V bulb connected across the main power connector? Very strange... I have done that whenever I've been disposing of a battery and have never had any issue getting all cells down to 0.1-0.2V, by which point there is essentially zero energy left in the pack anyway. Did you actually check the voltage of each cell? Yes, I always check the cell voltages before disposal and I have never seen a cell higher than 0.3V following this method. However I should also say that compared to many people I do nanny my batteries throughout their lives (always discharged to storage if going to be left unused >24 hours, lots of attention paid to battery cooling in installs and and I don't have any planes that really push battery performance other than an EFXtra which is as yet unflown). As a result when I dispose of them it is generally because their general performance is not matching expectations after a long cycle life (I have at least 300 cycles on several of my packs and a couple recently disposed of that had gone >500), not because they have been abused by high C discharges to the point of puffing and individual cell failure. They are normally still well balanced at the time of the final discharge, which I guess makes a situation like you observed less likely. Edited By MattyB on 13/03/2017 13:14:18 Quote Link to comment Share on other sites More sharing options...
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