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I have a particular case, where I purchased a brand new LiIon battery for an iPhone SE that showed 3.82 V in the beginning. I connected the battery to the circuit and after an hour or so, it showed 2.7 V. Then I disconnected the battery from the circuit, and kept it aside. Now after few days, the battery shows 0V. Does it mean the battery is faulty or it just needs to be recharged?

On a similiar note, does the NiMh and Alakline battery also have threshold voltages, below which they arent usable anymore and needs to be recycled?

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  • \$\begingroup\$ Read the spec sheet and it will tell you. Specifically you need to know if there is some protection circuit on the battery to prevent you killing the battery or you really did kill the battery. \$\endgroup\$ Jan 9, 2018 at 23:41
  • \$\begingroup\$ Whether an Alkaline cell should be discarded or not depends on what you are using it in. Cells that won't run my camera may be quite adequate for use in lower-drain devices. for rechargeable cells, you should recharge them before they are fully discharged - deep discharges do more damage to the cells than shallow discharges and frequent charging (provided you don't over-charge the cells.) \$\endgroup\$ Jan 9, 2018 at 23:44
  • \$\begingroup\$ @PeterBennett So, the 0 V on the Li Ion battery doesnt mean anything? 0 V is not an evidence, that the battery is kaputt? It just means, that it needs to be charged. Is my undersanding correct? \$\endgroup\$ Jan 10, 2018 at 9:11
  • \$\begingroup\$ @infoclogged Try charging it. It's possible that the internal protection circuit has detected that the battery is below the minimum voltage and shut down the output until it's recharged. \$\endgroup\$
    – Simon B
    Jan 10, 2018 at 9:12
  • \$\begingroup\$ @SimonB The battery doesnt charge. The problem is that I dont know if the charging unit inside the iPhone is dead or the battery is dead. If anyone would have said, that 0 V means dead, then there would have been no discussion anymore. But it looks like that the internal protection unit has shut down the output..However, I was looking for a proper answer and not speculative. \$\endgroup\$ Jan 10, 2018 at 9:22

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It's more than likely that the protection circuity has shut off all access to the battery due to it being over-discharged.

Li Ion is an inherently dangerous battery chemistry and lots of precautions are made to try and make it safe, one of these is effectively a fuse in the protection circuity that when over-discharge of the battery occurs effectively bricks the battery - without diverting the protection board at least (tip: don't do this).

The problem is that in an overly discharged Li Ion, tiny needle-like crystals begin to form in the liquid electrolyte. These crystals can eventually bridge the anode & cathode causing an internal short in the battery, usually leading to fire and/or an explosion. Here's a video demonstrating what happens to a shorted lithium ion battery.

Even though the battery is showing 0v there probably is still some charge left in the battery, but it has dropped below a voltage at which the battery can now be considered "unsafe" and the protection circuitry has broken the connection between the battery terminals and the terminals exposed for connections (probably where you are testing). In other words, the terminals you are using to test the voltage of the battery are probably not the terminals of the actual battery itself, there is probably a tripped fuse somewhere between the actual terminal and the point at which you are testing.

For reference, according to The Journal of Chemical Thermodynamics (referenced on this Wikipedia page)

Lithium-ion cells are susceptible to damage outside the allowed voltage range that is typically within (2.5 to 3.65) V for most LFP cells. Exceeding this voltage range, even by small voltages (millivolts) results in premature aging of the cells and, furthermore, results in safety risks due to the reactive components in the cells.

As @BruceAbbott pointed out in the comments the quote above specifically talks about Lithium Iron Phosphate (LiFePO4)batteries that have a slightly different safe range than standard Lithium Ion. For LiIon the range is typically 2.7-4.2V.

NiMh and alkaline batteries do not suffer from the crystal growth issue, as far as I am aware.

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  • \$\begingroup\$ NiCad certainly does suffer from crystal growth, though it happens under circumstances different from lithium cells. If you fully charge a Nicad and then store it for a long time, crystals will grow and puncture the internal insulator layers. This will discharge the cell, and short out the cathode/anode. If you REALLY need to use a Nicad that has died this way (like, while waiting for the replacement to arrive) then you can zap it with high voltage and high current to remove the short. It won't have full capacity, and it will have a very high self discharge rate. \$\endgroup\$
    – JRE
    Jan 10, 2018 at 12:01
  • \$\begingroup\$ NEVER EVER apply the high voltage/high current trick to a lithium battery. \$\endgroup\$
    – JRE
    Jan 10, 2018 at 12:02
  • \$\begingroup\$ The statement at which the battery can now be considered "safe" and Lithium-ion cells are susceptible to damage outside the allowed voltage range... seems contradictory to me. Can you please explain. I was expecting "unsafe" rather than safe. \$\endgroup\$ Jan 10, 2018 at 13:53
  • \$\begingroup\$ How much voltage is exactly this dropped below some voltage? A range will do. If its battery specific, I am talking about iPhone batteries. \$\endgroup\$ Jan 10, 2018 at 13:57
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    \$\begingroup\$ @BruceAbbott, that should be Lithium Iron Phosphate - LiFePO4 \$\endgroup\$ Jan 10, 2018 at 19:14

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