OT mobile phone battery

[alan_m]

Last week while making a phone call on my mobile it cut off with no battery power after around 40 minutes although previously it had been plugged in charging for a lengthy period (days). Further investigation showed that the battery would charge from 0% to 100% in a very much shorter time than normal and the phone would switch off when the battery indicator was 20%. On checking the removable battery I found that it had bulged out by around 2mm on the thinnest side. A new (compatible) battery has been obtained and all is back to normal.

I wonder if the failure of the battery was because during lockdown the phone had been left continuously on charge for lengthy periods of time (days)? During normal times I would take the phone off charge and take it out with me every day but with the stay at home regime there is no need. When left on charge this Samsung phone seems to charge up to 100% and then over time gradually the charge indicator gets to around 95/97% at which point charges again to 100%. Would this constant topping up of the last 5% cause the battery to fail in this way, and with a very noticeable physical bulging?

[The Natural Philosopher]

no. all my 'bulgy' packs have been either over discharged, or just had internal faults hat developed over time. 4 -6 years seems to be good going for pack.

[Theo]

It's possible. It's more stressful on lithium cells to be at the top end of their voltage range (above 4.1V say), and repeatedly charging/discharging at this point puts a lot more wear on the battery than repeatedly going between for instance 50% and 55%. The bulging is due to gas buildup from electrolyte decomposition.

This is why phones (and electric cars) only fast charge to 80% - the battery will last longer if it's not used to maximum capacity, and the last few percent of the charge curve is the most stressful.

Your phone may have a setting where it can limit charging to 80% if it's going to be plugged in a lot.

Theo

[Martin Brown]

I'm not sure sure about that. Some of the dumber maximum duration when in use charging regimes are rather close to causing gassing. If you leave the thing on charge all the time it may cause trouble.

Most of the ones I have seen fail have died due to old age. I generally kill my laptop batteries this way by running them on mains too much.

[Dave Plowman (News]

It really does depend on the electronics. My last laptop would killed the battery in months if left plugged up.

This newer one, not. It is normally left plugged in, and when I used it on battery a few weeks ago, the life seemed normal.

[Jeff Layman]

My laptop runs almost continuously plugged in, and is now just over 6 years old. The power monitor reports its battery capacity is 77.0% of design (59.2 vs 77.0Wh). I don't think that's too bad.

[The Natural Philosopher]

I would say that that is probably par for the course.

Half life of 6-8 years in terms of capacity.

[jon]

I have an Acer A1 2010 vintage smart phone, I haven't used it for 8 years now, but test it now and again. It has been on constant charge.

[Martin Brown]

How long does it actually run for when not on mains power though?

[Brian Gaff (Sofa]

Batteries just tend to do thatI mean bulge. I have a number of them here which power other devices. I'm not sure, but I deduce its not the actual charging, but the number of cycles. Brian

[Jeff Layman]

I just pulled the power plug, and it tells me there is 1.4 hours left until the battery is empty.

[Harry Bloomfield, Esq.]

It happens that alan_m formulated :

The modern Iphone software suggests it can predict your usage of the phone, so it will only try to maintain a full charge when you are likely to need to take it out with you. The rest of the time it just maintains a less than full charge.

[Fred]

That's overstated. Mine charges fully almost all the time.

Maybe it finds it hard to work out which days I will be going out, but it should be able to work out that I am hardly ever out long enough to need a full 100% charge.

[Martin Brown]

They have improved somewhat over the years but the general rule of thumb is that if the battery is kept fully charged and too close to the maximum possible charge capacity it will eventually start to gas.

Chargers have improved somewhat over the years but the marketing requirement for maximum runtime when used as a portable in benchmarks and the long term battery longevity are always in conflict.

[Dave Plowman (News]

I'd be most surprised if many unplug their battery when running on mains. And with lockdown, mains is likely the norm for most.