Are Li-Ion batteries tougher than we think? (deep discharge)

[tailland]

About 2 weeks ago, I re-discovered a Samsung tab (I thought I had lost almost a year ago) in a pile of otherwise useless stuff at home. I had little hope it would charge again, since it has been lying there all the time... but it did. Without problems. Plugged it in the charger, it charged to 100%, turned on, held its charge.

I didn't mention it here, because after all, it might've been a fluke, but what happened today is nothing short of a miracle.

While clearing out my place, I discovered an old mobile phone, A Sony Ericsson K800i which I bought in 2006, and which I had put back in its box in 2009 when I bought my first smartphone. Remembering what happened 2 weeks ago, I got curious if it...still worked.

You know what's coming next, don't you?

I connected it to its propietary charging cable, plugged it into the USB wall charger... and guess what: Yes. It did charge. Without hassle. I turned the phone on, the battery holds its charge and I'm amused to have a phone from last decade lying on my desk. Here it is...


How on earth is this possible? I thought Li-Ion batteries react so badly to deep discharge... how did this phone's battery re-activate so easily after 9 years ?!? Those little things must be tougher than I had ever imagined...

 

[Baditude]

I'm currently using my deceased mother's old Trac Phone, because I moved and my own flip phone often experienced drops and missed calls because of the poor reception in the rural area that I currently live. This Trac Phone must be at least 12 years old and only holds a charge for about a day or two. But it works better than my newer flip phone.

I won an original innokin MVP back in 2013 (5 years old). It's now just a backup for my sister, but it still works although it also doesn't hold a charge for long.

Battery duty cycle refers to the approximate number of recharges a battery can be “cycled” through before the battery will no longer hold a charge. Duty cycles can be up to 500 charges but will vary depending on the core battery composition. They will begin to lose their ability to hold a full charge somewhere between 250 - 300 charge cycles.

I'd question the current amp rating and capacity of any cylindrical high drain cell (or battery) over two years old. As a battery ages the mAh of the battery degrades, as the mAh degrades so does the battery'a C rating (amp limit). So down the road, a 20A battery may only be a 10A battery.

 

[sonicbomb]

I thought Li-Ion batteries react so badly to deep discharge... how did this phone's battery re-activate so easily after 9 years ?!?

I know what a deep or damaging discharge is on an 18650. But I have no idea what the same is on a mobile phone battery let alone the specific cell in yours.
Applying Occam's razor, I suggest that by by chance there was an optimal storage charge in the battery, and that the quality of the battery is really good. It has taken a charge, but it would be interesting to see how it actually performs under normal use.

I think we have gotten so used to the massive power requirements of modern smart phones that we have forgotten how long a charge lasted on old school phones. My last Nokia used to go nearly a week of normal use without a charge up.

 

[untar]

It's a misinterpretation of why certain conditions in LiIon batteries are considered bad. It's not like they 100% instantly die, it's that the chance of catastrophic malfunction significantly rises. With our higher powered batteries that's no joke so we prefer to simply not use them any more and don't encourage anyone to make experiments and take chances.

Some guy could say "I pulled 50A from my Sony VTC5A and it didn't go boom" but that doesn't mean it's advisable or that the battery wouldn't get abused at all if that was done on a regular basis. Just the same it means nothing that you got one battery that sat around for years without use and now took a charge again. You neither have a sample size of any shape nor know how far the chemistry has degraded in that time frame.
I wouldn't dare to base any general rule on that one observation.

Add to that that old phone batteries have a vastly different use case and are designed differently from the cells we use and you're miles away from a "surprising" discovery about all LiIon cells (like your title suggests).

That said, the batteries can take more abuse than the recommendations you see on forums and YT, we're not operating them at the very edge of their capabilities (nor should we), it's about minimizing risk.
Deep discharge, damage to the can, shorting (that includes Amp draw way over the CDR) and especially overcharging all increase the risks involved so we tend to advise to avoid those scenarios. It's simply safer to just buy a new cell, they're not that expensive.

 

[Barkuti]

…
How on earth is this possible? I thought Li-Ion batteries react so badly to deep discharge... how did this phone's battery re-activate so easily after 9 years ?!? Those little things must be tougher than I had ever imagined...

What do you believe/think is a deep discharge? Li-ion cells are usually specced for discharge down to 2.75/2.5V, and some even down to 2V.
A battery inside a device is connected to a built-in battery management system which of course prevents any chance of battery over-discharge. Smartphones generally auto shut down much before the battery voltage gets close to the above values, in my experience they rarely go below 3.4 - 3.5V under load and I've never seen it go below 3.1 - 3.2V. Thus, it is pretty normal for an unused smartphone battery to endure for years. Heck, I have an ooold li-ion powered MX1000 laser mouse (from 2002 LoL) and it still works.

Cheers

 

[Imfallen_Angel]

It's just a question of quality.. and how the device manages it's power/battery. I have a lot of devices that are over a dozen years old now, and some have batteries that are absolutely fine, others that the battery is done for and requires to be changed.

I've had some devices that the batteries barely lasted a year, others that have lasted several.... heck, my best example is my cell phone (Pre3) that I still use every day, is from 2010-11 (so over 7 years old), and the original battery was still in the 90+% strong (94% I think?). I've switched it to one of my backups last year to stretch them and.. (opening the battery testing app...) it is now reading at: health at 98% (1194mAh /1218mAh rating). At this rate, I'm probably good for another several years.

So while your devices' battery are still working fairly well, they may have lost anywhere from 5 to 15% of their original capacity.. if you have testing capacity, you'd get a more accurate idea, but as long as the devices were in a cool area, the devices off, the chemical composition well balanced, weren't overused before being put away, batteries can last a fairly long time.

It's really hard to judge any battery to be honest, as there's so many possibilities.