Drove 5V into a Li-ion cell for just one second, should I be worried?

bwDraco

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While testing a faulty device, I unexpectedly drove 5V USB into a protected NCR18650B cell for about one second. The voltage of the cell itself did not exceed 4.3V, which is inside the 4.35V safety limit, and settled to below 4.1V when power was removed, but I'm not sure if the cell is still safe to use.

Should I be worried?

Draco


Hmm... So I did some research and found that the effect of overcharging is plating of the anode (negative electrode) with lithium metal, the same that would happen if one attempted to charge Li-ion in below-freezing temperatures. After some thought, I kinda think the battery is still usable given the brevity of the event and the peak voltages reached, but I will be monitoring the battery closely during the next few charge cycles using an IR thermometer.

Is this okay, or should I replace the cell?
 
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Dr. Mario

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I'd not worry too much about this as that's how some superfast Lithium-ion battery chargers work - the trick is to know when to quit (Qualcomm QuickCharge rings any bells?). They do so by measuring both cell open voltage and charging current, while also monitoring the cell temperature, with the cell fed 5 Volts (on Qualcomm QuickCharge capable phones, that occurs at 6 - 9 Volts via USB voltmeter) at set current, it then drops to 4.4 Volts once nearing completion of charging process (at 80%). That's how you go from 0% to 70% in fifteen minutes in certain cases.
 
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SilverFox

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Hello Drako,

It usually takes some time to do damage. You are most likely OK.

However, mark the cell and keep an eye on it for the next few cycles. If it doesn't show any irregularities then you can just use it. If you see something strange showing up, recycle the cell and move on.

Tom
 

HKJ

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I'd not worry too much about this as that's how some superfast Lithium-ion battery chargers work - the trick is to know when to quit (Qualcomm QuickCharge rings any bells?). They do so by measuring both cell open voltage and charging current, while also monitoring the cell temperature, with the cell fed 5 Volts (on Qualcomm QuickCharge capable phones, that occurs at 6 - 9 Volts via USB voltmeter) at set current, it then drops to 4.4 Volts once nearing completion of charging process (at 80%). That's how you go from 0% to 70% in fifteen minutes in certain cases.

The QuickCharge protocol has nothing to do with how the battery is charged, it only controls the power delivered to the phone. Circuits in the phone controls the actual charge.
The internal charge algorithm in the phone may do crazy stuff like applying more than 4.2V to the battery (This is dangerous to do with any battery except the one certified for it, i.e. the original battery).

For people interested in usb power delivery this article may be interesting: http://lygte-info.dk/info/USBinfo UK.html
 

Lynx_Arc

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If the battery was a protected cell there shouldn't be any problems as when the battery hit the "danger" zone the protection circuit would have tripped. Most likely the 5v source caved in voltage when the battery tried to draw more current than it could provide also.
 

bwDraco

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Thank you all for the advice. I haven't noticed any abnormalities thus far - temperatures during charging are well within normal limits and the cell is performing as expected. I did not manage to trigger the overvoltage protection; IIRC the highest voltage I saw the cell register on my multimeter was 4.28V.

I'll just monitor it closely for a bit more and will probably give it a clean bill of health.

Draco
 
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