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Is this battery safe??

Discussion in 'Electronics' started by Stack15, Jul 12, 2018 at 6:48 PM.

  1. Stack15

    Stack15 Well-Known Member

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    59B45047-EB0A-4A56-B701-4B360B10C3C9.jpeg 31F2569A-150E-45B6-9A12-37F02B9894F2.jpeg 209ABF31-F263-45CC-A9D9-EB6DE8EFDC25.jpeg I bought a car off eBay and it came with a 3S LiPo Venom 4000 20c. It does not sit flat on a table like my 2S Lipos do. It seems to have some curves.

    Is that normal for a 3S?

    Also I ran it until it was dead - wouldn’t turn the car wheels anymore. I charged it back up and my charger said it received 1,687.

    Are these signs the thing is bad?
     
  2. cnk

    cnk Well-Known Member

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    That pack is puffed and I personally wouldn't want to risk running it anymore. When you say you ran it until it was dead, do you mean you hit LVC or that you drained the battery completely? You should not take a LiPo below 3.V/cell or bad things can happen.
     
  3. joostin420

    joostin420 Well-Known Member

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    That battery looks puffed alright. I would decommission that one. 20c is a little on the low side.
     
  4. Jerry-rigged

    Jerry-rigged Premium Member!
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    No good news here...

    Yeah, the curved sides of the battery is a sign that at least one of the cells has "puffed" - when Lipos get stressed to the point that they start to fail, they start internally off-gassing, and the plastic bag that holds the cell swells up like a balloon. If the cell ruptures, it will probably catch on fire! So IMHO, this battery is done.

    Best is to make a bucket of salt water, and (outside) drop the battery in and leave it for 24-48 hours. This will kill it to 0v. Then toss into the regular trash.

    Second - make sure your ESC is set to Lipo mode. The way your phrased "ran it till dead" - did it run mostly strong, then suddenly stop? Or did it slowly slow down? In the first case, all is good, in the second case, you may have run it down too far - below 3.0v per cell.

    What kind of charger do you have? If it was safely at LVC, it should take a lot more than 1687mah. If it was below 3.0vpc, most chargers won't even try to charge it.
     
  5. Paultro84

    Paultro84 Well-Known Member

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    Most lipos say no lower than 3.2 volts per cell. It looks unsafe to me. I'm not sure how we're supposed to properly dispose of junk lipos.
     
  6. Stack15

    Stack15 Well-Known Member

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    I have the fancy $100 venom charger. The battery was described as “in good shape”.

    The car ran strong. Very strong. And then it just wouldn’t go anymore. I thought it broke but when I hooked a different battery to it - very strong again.

    I put this battery in a lipo case and in my giant grille - while we decide what to do with it. Sadly I thought of it as a $50 value in the purchase of the car. Apparently it was not.
     
  7. cnk

    cnk Well-Known Member

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    I purchased some 12V 25W automotive light bulbs from Walmart and wired them in series with some alligator clips. I then connect them to the battery outside on the concrete and let them discharge. You will want to have some sand or a fire extinguisher nearby just in case. When the bulbs stop lighting up, leave them connected for a couple more hours as they will still be draining the battery.

    Once the cell voltages are .1V or lower you can dead short the battery. You can either dispose of them in the garbage or drop them off at a recycling center.

    As for cells that go below 3V/cell, some of the higher end chargers have the ability to try to save them. My Revolectrix PL8 was able to save a 6S pack I had where 1 cell was down to 2.6V.
     
  8. Stack15

    Stack15 Well-Known Member

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    Charger.
     

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  9. WoodiE

    WoodiE Kind of good admin
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    Nope. That bad boy is beyond "a little puffed". Dispose of it and get a new one!
     
  10. Jerry-rigged

    Jerry-rigged Premium Member!
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    Yeah, this seems to be common when buying a used car with a lipo included - the lipo ends up being crap. Same happens to all of us, eventually. Best is to count lipos as $0 value, unless you can inspect them before hand, or know the seller.
    To me, this sounds like the LVC is working fine. So if you ran it to LVC, and your charger would only put 1700mah in a 5000mah battery, then that is another sign of an issue. However, it could also be charger settings - what mode were you in, what amp charge rate? About how long did it take to charge? Voltage (total and cell) at the end of the charge?
     
  11. olds97_lss

    olds97_lss Premium Member!
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    I have some SMC 9000mah lipo's that are "a little puffed". After a year or so's worth of running, they didn't like fitting in my ERBE battery bays anymore. One of them actually dropped a cell, so I did what others here suggested, used automotive lights to drain it, then soldered the leads together to keep it from recovering.

    I still charge the others and use them though. They take longer to balance than they used to and they don't run as long either. I've kind of stopped using the big packs though. Adds weight and I don't get a whole lot of extra run time out of them vs the 7400's I run. The 7200/7400 (were 7200 last year, now SMC is selling 7400) fit in all my trucks, so I'll probably just stick with those from now on. The 9000's fit in my ERBE and Savage, but not my ejato and stampede 4x4.

    [​IMG]
    [​IMG]
     
  12. Paultro84

    Paultro84 Well-Known Member

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    Some chargers you have to set the battery size, the mah. So if it's a 5000mah battery and the charger is set to say 4000mah, you'll never get a full charge.
     
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