cell phone battery behavior near the end

[wrcsixeight]

I am trying to determine if my cell phone is not charging the battery, or the battery is just not capable of taking a charge.

Last couple months I would plug it in overnight, and seldomly it would go dead, yet recharge when plugged back in.

The battery life has been pretty good, playing music for hours through the speakers, or lasting through a long conversation.

This morning, I pulled if off the charger and it said 1 out of 3 bars on the battery strength.

Plug it in, says it is charging, take it off after an hour, low battery alert comes up instantly

Check battery voltage. 3.543 (3.7v battery)
Insert needles in contacts with battery in phone and attached to charger. 3.712 volts.

I've tried 3 different charging sources, AC and DC same result

Contacts on battery and in phone have been cleaned but were not dirty. Charging port appears pristine.
A new battery is 6$ delivered, but earliest arrival is a week away.

Don't want to have to upgrade phone at this point.
Phone is 3.5 years old
Pantech p7000

Don't want smartphone.

Anybody have any insights whether the battery itself if toast or if the cell phone has decided not to charge it?

 

[renegade_987]

If the cell phone still powers fine it sounds like you need a new battery

 

[JHZR2]

Batteries can fail by a number of mechanisms, but generally capacity can fade because of inability of ions to intercalate in and out of the material structure, impedance growth due to increased SEI layer, soft short circuits, etc.

It sounds to me like there is fade due to a lack of ions, perhaps due to Li plating out, or else an SEI so thick, that the ions cant transfer. That means that the battery can show the right voltages sometimes, but depending upon temperature and other conditions, it may or may not perform.

 

[renegade_987]

Originally Posted By: JHZR2
Batteries can fail by a number of mechanisms, but generally capacity can fade because of inability of ions to intercalate in and out of the material structure, impedance growth due to increased SEI layer, soft short circuits, etc.

It sounds to me like there is fade due to a lack of ions, perhaps due to Li plating out, or else an SEI so thick, that the ions cant transfer. That means that the battery can show the right voltages sometimes, but depending upon temperature and other conditions, it may or may not perform.



That got waaayyyy to technical

 

[wrcsixeight]

Well the battery is ordered, but I am not sure it is the battery itself which is bad.

If it is, it was a rather abrupt failure.

But I am not experienced in Li-ion battery failure, or how charging voltages are applied.

Apparently a fully charged 3.7v Li-ion battery reads 4.2 volts.

I am only seeing 3.7xx when the charger is plugged in and attempting to charge the battery.

The charging port is some proprietary plug that seems a little flimsy, and perhaps has broken internally, and thus the new battery I will wait a week for, might do nothing but drain me of 6$ and perhaps I would be better off getting a new phone sooner.

 

[michaelluscher]

On eBay, under 10$ gets a new Battery + AC wall charger.
Some bundles even throw in a Car Charger.
For that money, my experience says if you like the phone, Just replace them.

 

[The_Jeff]

I suspect the firmware in your phone is messed up but I'm just on a lark here.

Maybe it "remembers" how much time it spent charging and gives you "battery bars" based on that. Since it doesn't remember charging it plays it safe and gives you one bar.

Let us know how the new battery does.

 

[JHZR2]

Originally Posted By: wrcsixeight


But I am not experienced in Li-ion battery failure, or how charging voltages are applied.

Apparently a fully charged 3.7v Li-ion battery reads 4.2 volts.

I am only seeing 3.7xx when the charger is plugged in and attempting to charge the battery.

The charging port is some proprietary plug that seems a little flimsy, and perhaps has broken internally, and thus the new battery I will wait a week for, might do nothing but drain me of 6$ and perhaps I would be better off getting a new phone sooner.




Usually constant current, then constant voltage.

4.2V roughly is right for "traditional" Li-ion chemistries. 3.7V is the nominal rating. If your charger isnt going above 3.7V, then the battery will not fully charge, and it is likely the sign of an issue - the charger is current limiting, and can only put out 3.7V, say, at its full current rating.

Sounds to me like you have a soft internal short. Not big enough to heat the battery abusively, but enough to keep the cell from charging properly.

 

[wrcsixeight]

I left the phone pluggin in all night.

Woke up to 3 bars of battery(full).

Just had a 30 minute convo
Battery reads 4.11 volts.

Bizarre behavior

 

[jrustles]

Originally Posted By: wrcsixeight
I left the phone pluggin in all night.

Woke up to 3 bars of battery(full).

Just had a 30 minute convo
Battery reads 4.11 volts.

Bizarre behavior


What Phone?

I have an old Motorola XT300 (Android Eclair) that has firmware issues where occasionally it selectively charges. That is, it has the same behavior as your phone; plug it in, thinking it's charging, but it's not. It's really discharging. Unplug it and depending on how long it's been 'fake charging', It'll show the low battery and dimmed screen instantly. It doesn't happen often, but when it does, it's annoying. I pull the battery out, put it back in and reboot problem solved. It's done this since new btw, but again not often.

 

[wrcsixeight]

It is a pantech p7000.

The battery indicator is still reading 3 bars without being recharged. It did shut itself off once since which is pretty rare.

I think the battery itself is fine and either the phone is not charging it sometimes, or there is a intermittent connection in the proprietary pantech charging plug.

I'm going to let it run till the low battery warning comes on, then attempt to recharge

 

[wrcsixeight]

The battery life seems normal when it does charge, lasting days.
The battery was reading one bar last night, and I plugged it in.

It said it was charging, then died when I took it off the charger a few hours later.

Off/ON twice plugged it back in and charged again, now 3 bars.

Must be having its period.

 

[wrcsixeight]

New battery arrived just now.
measured 4.11 volts.

I put my clamp on DC ammeter on my 12v Blue sea USB oulet, and when first plugging the phone in to charge, it was reading 0.19 amps.

A few minutes I look over and the the ammeter is showing -0.03 amps, showing that power seems to be flowing from the phone.

Unplug it, replug it, and 0.19 amps again.

The phone was indicating charging, even when it was apparently backfeeding the USB supply.

Wiggling the cord at wither connection has no effect on amps consumed, and so far I have not seen it return to -0.03amps since that one time.

It has tapered to 0.10 amps since I started typing

 

[wrcsixeight]

The new battery's life is not really any better than the old battery, and I am still having issues getting it to charge.

Basically every time I plugged it in today to a DC source with an ammeter clamped over a wire, or a DMM hooked inline, my Ammeter said 0.05 to 0.02 amps were flowing out of the phone.

I was able to get it to start charging only by removing the battery from the phone, while the phone was still on, and returning the battery while still plugged in.

It is now accepting 0.22 amps.

Whenever the phone is plugged in, it indicates it is charging, even when it is discharging, or just doing nothing. Even if it is on with the display on and browsing the net the ammeter was reading that it was either backfeeding the USB power source, or completely neutral, all whilst indicating it was charging.