How much current can be produced from a battery cell

Discussion in 'Power Electronics' started by Kelvin Lee, Apr 11, 2019.

  1. WBahn

    Moderator

    Mar 31, 2012
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    For that to be the case, you have to be assuming that within that cell there really is an ideal 1.5 V voltage source.

    You also have to be assuming that ALL of the heat being produced is coming ONLY from resistive joule heating -- that there isn't any heat being produced due to chemical reactions. You also have to be assuming that there aren't any other mechanisms at play, such as the production of hydrogen gas.
     
  2. Raymond Genovese

    Well-Known Member

    Mar 5, 2016
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    I do have a healthy respect for batteries and particularly those contain Li. Not posting on that issue, but instead on the OP's title question. As a result of reading some of the responses here, I did some reading in http://data.energizer.com/pdfs/lithiuml91l92_appman.pdf which is for the batteries I mentioned in post #6. I did not know and was pleasantly surprised to learn that there is, essentially, a resettable thermal switch in these batteries to prevent excessive current draw (I mean the PTC not the vent hole).

    From p14.

    These two safety devices are a resettable thermal switch or PTC (Positive Thermal Coefficient) and a pressure relief vent. The PTC protects against electrical abuse scenarios by limiting the current when the PTC temperature exceeds 85°C. As the battery heats during abuse, the resistance of the PTC rapidly increases and significantly limits the amount of current flowing through the battery, thus allowing the battery to cool. When the PTC cools to below the activation temperature, its resistance returns to a normal level allowing normal battery use.

    I thought that was pretty interesting - not sure all cheapo batteries have that, but this one does.
     
  3. Tonyr1084

    Distinguished Member

    Sep 24, 2015
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    I once got my hands on some "Mercury" cells. It was a very long time ago but I can swear they were "Mercury" cells. They came out of an old emergency light. The kind that light up during power failures. I got a hold of them because they would no longer take a charge. No matter what I did - they would not charge. But wait a minute! I accidentally reverse charged them one night. The next morning when I went to check on them to see what was going on I discovered the reverse charge. Immediately frightened, thinking I nearly burned down the house, I disconnected them as quickly as possible. And they were not hot. Basically were at room temperature. So I figured if they were bad before they must REALLY be bad now. I accidentally touched the two wires together and they instantly welded together, the wire got very hot very fast and the cell itself was rapidly building thermal energy. I could barely pull the wires apart and the cell was shorted for probably between 2 and 5 seconds. Once the short was broken the battery was nearly too hot to hold. I let it cool, then checked the voltage, and again I swear this to be true, they held a reversed charge. Positive was now reading negative and the negative was positive. I SWEAR this was the case. It was back in 1983, so memory might be in error, but I'm pretty confident this is as I remember it. I will admit there is the possibility I properly charged it and just had my meter leads plugged in backwards - or some other "Logical" explanation; but I think I took the measurements correctly. If this had never happened to me before and someone else was telling this story I would be (for my part) convinced they measured it wrong. But as best as I can recall, this story is accurate.

    This (these) mercury cell(s) were a little larger than a D cell battery. And boy did this one get real hot real fast! Explode? I believe it could have.
     
  4. Audioguru

    Expert

    Dec 20, 2007
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    The Energizer Lithium AA cells are MUCH more powerful than their alkaline cells. Guess what? They are also MUCH more expensive.
    I was given samples of them and they are much better than alkaline, but I never bought any.
     
  5. oz93666

    Senior Member

    Sep 7, 2010
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    More to the point is , just what sort of useful output can you get at high currents .. Of course when truly shorted all the output goes to heat the cell , but at about 5A around half the total output is usable ... Energizer only give AHr capacity at low currents , but the trajectory is sharply down, at 5A you can perhaps only expect a tenth of the capacity you get at 25mA.... not the case with lithium cells .

    [​IMG]
     
    Last edited: Apr 14, 2019
  6. oz93666

    Senior Member

    Sep 7, 2010
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    Lithium can only produce voltage of 3 - 4.2 , so I'm not sure how they can make an AA lithium cell unless it contains electronics to step down the voltage to 1.5 ???

    Edit ... After a search it appears this cell is not lithium after all !! not rechargeable ...they've just trade marked the name 'Lithium'
    The gangsters just guarantee it won't leak chemicals into your remote control , destroying it , as their standard product is designed to do. No doubt the company gets a kick back from electronics manufacturers.
     
    Last edited: Apr 14, 2019
  7. Raymond Genovese

    Well-Known Member

    Mar 5, 2016
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    Well, it is a battery and it has lithium in it...http://data.energizer.com/pdfs/lithiuml91l92_appman.pdf Also it looks to me like the trademarked Energizer®. Trademarking Lithium would be difficult, no?

    Energizer® lithium iron disulfide differs from alkaline batteries in chemistry and construction. ..Lithium is the lightest, most active metal. When this powerful metal is paired with iron disulfide, this energy is available at a voltage suitable for 1.5 volt applications.
     
  8. oz93666

    Senior Member

    Sep 7, 2010
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    Yes ... I was too hasty ...it's as you say , they've developed some strange type of lithium cell to get the required 1.5 , not rechargeable , but better suited for higher currents.
     
  9. Yaakov

    Well-Known Member

    Jan 27, 2019
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    Just for the record, not all lithium-based cells are rechargeable, just like this one there are higher voltage lithium primary cells used in extreme applications. They aren’t cheap but they are long lasting and rugged with very good temperature tolerance.
     
  10. Tonyr1084

    Distinguished Member

    Sep 24, 2015
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    Scroll to 16 minutes on this battery teardown. And no - it's not recommended you pull batteries apart.

     
  11. Yaakov

    Well-Known Member

    Jan 27, 2019
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    Clive loves to take batteries apart. Most people shouldn't act like Clive, he's special.
     
  12. MrAl

    AAC Fanatic!

    Jun 17, 2014
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    The maximum current from a battery is based on the internal resistance but drawing that max current usually means voiding the manu's specs and also means the voltage falls too low to be useful.
    For example, if you short a 9v battery you get max current but zero volts. SO what good is that.
    Maximum applied power occurs when the load resistance matches the internal resistance but that is also usually too much for the battery.
     
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