[EE] LiOn battery stress / Trickle charge a smartphone?

[Mario]

Hello,

Smartphone with non-removable LiOn battery: it will be turned off and
not used for many months, perhaps even 1 or 2 years. Do you think it
is better to keep the PSU attached though, or leave the smartphone
externally unpowered for all this time?

And what if a smartphone is always turned on (to receive phone calls)
instead but most of the time it is kept on the desk, is it better to
leave the charger always connected in this case?

I think it's always better to leave the PSU connected (because it
will make the battery work, and thus wear, way less), but it puzzles
me to see those messages like "battery is 100% charged now, disconnect
the charger", like to hint that it's no good to leave it connected.

Chers,
Mario

[Van Horn, David]

Generally for long term storage the cells last longest if about 75% charged and left without a load.
Keeping the cells fully charged puts maximum electrical stress on the cell.

If it's in use, then I would keep the charger on. That's what I'm doing right now with my phone, have done for years, and I get good battery life on my phones.

I get that warning also, "to save energy" as if somehow the charger didn't stop charging which would be an explosively bad idea...



-----Original Message-----
From: piclist-***@mit.edu <piclist-***@mit.edu> On Behalf Of Mario
Sent: Tuesday, May 29, 2018 11:38 AM
To: ***@mit.edu
Subject: [EE] LiOn battery stress / Trickle charge a smartphone?


Hello,

Smartphone with non-removable LiOn battery: it will be turned off and not used for many months, perhaps even 1 or 2 years. Do you think it is better to keep the PSU attached though, or leave the smartphone externally unpowered for all this time?

And what if a smartphone is always turned on (to receive phone calls) instead but most of the time it is kept on the desk, is it better to leave the charger always connected in this case?

I think it's always better to leave the PSU connected (because it will make the battery work, and thus wear, way less), but it puzzles me to see those messages like "battery is 100% charged now, disconnect the charger", like to hint that it's no good to leave it connected.

Chers,
Mario

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist

[James Cameron]

In my experience it depends on the phone DC input, usually under
firmware control.

Measure current over time on the DC input to document behaviour.

Some phones reach charged state and disconnect the DC input, then draw
almost no current until either battery voltage falls, or estimated
state of charge falls below something like 90% or 95%, then they
reconnect until charged.

Some phones reach charged state and disconnect the battery, operating
from the DC input until the DC input is removed. Of these, some won't
track estimated state of charge during the self-discharge phase, and
some will.

One device I have goes one step further; if you leave it connected for
a week, it presumes you plan to leave it connected forever, and says
so; it disconnects the DC input until estimated state of charge
reaches 50%, then transfers the load to the DC input.

Thus it entirely defeats the idea of keeping the device _ready_ for
use on battery in this way.

[Richard Prosser]

An I have another phone with an annoying "feature".
If left on the charger it fully charges the battery, then stops charging
and runs the battery down. It will only recharge if the charger is
disconnected and then reconnected again. I wanted to use it as a webcam
but.....

For best battery life it should be charged to about 4V/cell. This
corresponds to about 70% charge. Above this voltage the anode degrades.
Below this voltage and the cathode degrades (so I'm told).
If you have control of the inner workings of the charger you could try
resetting the voltage to ~4V/cell (4V ?) and just leave it plugged in.

RP

Post by James Cameron
In my experience it depends on the phone DC input, usually under
firmware control.
Measure current over time on the DC input to document behaviour.
Some phones reach charged state and disconnect the DC input, then draw
almost no current until either battery voltage falls, or estimated
state of charge falls below something like 90% or 95%, then they
reconnect until charged.
Some phones reach charged state and disconnect the battery, operating
from the DC input until the DC input is removed. Of these, some won't
track estimated state of charge during the self-discharge phase, and
some will.
One device I have goes one step further; if you leave it connected for
a week, it presumes you plan to leave it connected forever, and says
so; it disconnects the DC input until estimated state of charge
reaches 50%, then transfers the load to the DC input.
Thus it entirely defeats the idea of keeping the device _ready_ for
use on battery in this way.
--
James Cameron
http://quozl.netrek.org/
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Mario]

Thank you all for the infos, I didn't know that 70-75% is the charge
that gives the longest life, very interesting indeed.

They (smartphone manufacturers) should add an option to stop charging
at 70-75% and maintain that charge, it would be very useful to extend
the battery life of those phones that spend most of their life on a
desk.

But then again, do manufacturers have interest to extend life of their
products after warranty periods? Probably not really much.

With kind regards,
Mario

[Van Horn, David]

My Lenovo laptop has one charge mode where it won't charge above 75% for that reason.
It also has a "fast charge" mode which gets you to nearly 100% quicker than normal.
Seems to work as advertised.

[Neil]

I recently started looking at LiPo charger ICs for a project.
Do you have any links to whitepapers etc on this 4V/70% charging threshold?
The voltage during charge is higher than the cell voltage and will vary
by temp. How is the 4V determined... by temporarily disconnecting and
cooling it off? Or is there some mapping/compensation to correlate the
4V at a higher temp?

Cheers,
-Neil.

Post by Richard Prosser
An I have another phone with an annoying "feature".
If left on the charger it fully charges the battery, then stops charging
and runs the battery down. It will only recharge if the charger is
disconnected and then reconnected again. I wanted to use it as a webcam
but.....
For best battery life it should be charged to about 4V/cell. This
corresponds to about 70% charge. Above this voltage the anode degrades.
Below this voltage and the cathode degrades (so I'm told).
If you have control of the inner workings of the charger you could try
resetting the voltage to ~4V/cell (4V ?) and just leave it plugged in.
RP

Post by James Cameron
In my experience it depends on the phone DC input, usually under
firmware control.
Measure current over time on the DC input to document behaviour.
Some phones reach charged state and disconnect the DC input, then draw
almost no current until either battery voltage falls, or estimated
state of charge falls below something like 90% or 95%, then they
reconnect until charged.
Some phones reach charged state and disconnect the battery, operating
from the DC input until the DC input is removed. Of these, some won't
track estimated state of charge during the self-discharge phase, and
some will.
One device I have goes one step further; if you leave it connected for
a week, it presumes you plan to leave it connected forever, and says
so; it disconnects the DC input until estimated state of charge
reaches 50%, then transfers the load to the DC input.
Thus it entirely defeats the idea of keeping the device _ready_ for
use on battery in this way.
--
James Cameron
http://quozl.netrek.org/
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Van Horn, David]

The best sources I know of are the McGraw Hill handbook of batteries (overkill but good reference) and the info online at Battery University.

-----Original Message-----
From: piclist-***@mit.edu <piclist-***@mit.edu> On Behalf Of Neil
Sent: Wednesday, May 30, 2018 11:32 AM
To: ***@mit.edu
Subject: Re: [EE] LiOn battery stress / Trickle charge a smartphone?

I recently started looking at LiPo charger ICs for a project.
Do you have any links to whitepapers etc on this 4V/70% charging threshold?
The voltage during charge is higher than the cell voltage and will vary by temp. How is the 4V determined... by temporarily disconnecting and cooling it off? Or is there some mapping/compensation to correlate the 4V at a higher temp?

Cheers,
-Neil.

Post by Richard Prosser
An I have another phone with an annoying "feature".
If left on the charger it fully charges the battery, then stops
charging and runs the battery down. It will only recharge if the
charger is disconnected and then reconnected again. I wanted to use
it as a webcam but.....
For best battery life it should be charged to about 4V/cell. This
corresponds to about 70% charge. Above this voltage the anode degrades.
Below this voltage and the cathode degrades (so I'm told).
If you have control of the inner workings of the charger you could try
resetting the voltage to ~4V/cell (4V ?) and just leave it plugged in.
RP

Post by James Cameron
In my experience it depends on the phone DC input, usually under
firmware control.
Measure current over time on the DC input to document behaviour.
Some phones reach charged state and disconnect the DC input, then
draw almost no current until either battery voltage falls, or
estimated state of charge falls below something like 90% or 95%, then
they reconnect until charged.
Some phones reach charged state and disconnect the battery, operating
from the DC input until the DC input is removed. Of these, some
won't track estimated state of charge during the self-discharge
phase, and some will.
One device I have goes one step further; if you leave it connected
for a week, it presumes you plan to leave it connected forever, and
says so; it disconnects the DC input until estimated state of charge
reaches 50%, then transfers the load to the DC input.
Thus it entirely defeats the idea of keeping the device _ready_ for
use on battery in this way.
--
James Cameron
http://quozl.netrek.org/
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist

[Richard Prosser]

Have a look at http://batteryuniversity.com/index.php/learn/ Bit of a
rabbit hole though!

RP


On 31 May 2018 at 07:02, Van Horn, David <

Post by Van Horn, David
The best sources I know of are the McGraw Hill handbook of batteries
(overkill but good reference) and the info online at Battery University.
-----Original Message-----
Sent: Wednesday, May 30, 2018 11:32 AM
Subject: Re: [EE] LiOn battery stress / Trickle charge a smartphone?
I recently started looking at LiPo charger ICs for a project.
Do you have any links to whitepapers etc on this 4V/70% charging threshold?
The voltage during charge is higher than the cell voltage and will vary by
temp. How is the 4V determined... by temporarily disconnecting and cooling
it off? Or is there some mapping/compensation to correlate the 4V at a
higher temp?
Cheers,
-Neil.

Post by Richard Prosser
An I have another phone with an annoying "feature".
If left on the charger it fully charges the battery, then stops
charging and runs the battery down. It will only recharge if the
charger is disconnected and then reconnected again. I wanted to use
it as a webcam but.....
For best battery life it should be charged to about 4V/cell. This
corresponds to about 70% charge. Above this voltage the anode degrades.
Below this voltage and the cathode degrades (so I'm told).
If you have control of the inner workings of the charger you could try
resetting the voltage to ~4V/cell (4V ?) and just leave it plugged in.
RP

Post by James Cameron
In my experience it depends on the phone DC input, usually under
firmware control.
Measure current over time on the DC input to document behaviour.
Some phones reach charged state and disconnect the DC input, then
draw almost no current until either battery voltage falls, or
estimated state of charge falls below something like 90% or 95%, then
they reconnect until charged.
Some phones reach charged state and disconnect the battery, operating
from the DC input until the DC input is removed. Of these, some
won't track estimated state of charge during the self-discharge
phase, and some will.
One device I have goes one step further; if you leave it connected
for a week, it presumes you plan to leave it connected forever, and
says so; it disconnects the DC input until estimated state of charge
reaches 50%, then transfers the load to the DC input.
Thus it entirely defeats the idea of keeping the device _ready_ for
use on battery in this way.
--
James Cameron
http://quozl.netrek.org/
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at http://mailman.mit.edu/
mailman/listinfo/piclist
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Van Horn, David]

When I was designing NIMH chargers on the AVR, this was one of my go-to sources.
Tempered by the data sheet of the specific cells we were using.

NIMH is a real pain to charge correctly especially if your charger has to operate in other than shirtsleeve temperatures.


-----Original Message-----
From: piclist-***@mit.edu <piclist-***@mit.edu> On Behalf Of Richard Prosser
Sent: Wednesday, May 30, 2018 2:20 PM
To: Microcontroller discussion list - Public. <***@mit.edu>
Subject: Re: [EE] LiOn battery stress / Trickle charge a smartphone?

Have a look at http://batteryuniversity.com/index.php/learn/ Bit of a
rabbit hole though!

RP

Post by Van Horn, David
The best sources I know of are the McGraw Hill handbook of batteries
(overkill but good reference) and the info online at Battery University.
-----Original Message-----
Sent: Wednesday, May 30, 2018 11:32 AM
Subject: Re: [EE] LiOn battery stress / Trickle charge a smartphone?
I recently started looking at LiPo charger ICs for a project.
Do you have any links to whitepapers etc on this 4V/70% charging threshold?
The voltage during charge is higher than the cell voltage and will
vary by temp. How is the 4V determined... by temporarily
disconnecting and cooling it off? Or is there some
mapping/compensation to correlate the 4V at a higher temp?
Cheers,
-Neil.

Post by Richard Prosser
An I have another phone with an annoying "feature".
If left on the charger it fully charges the battery, then stops
charging and runs the battery down. It will only recharge if the
charger is disconnected and then reconnected again. I wanted to use
it as a webcam but.....
For best battery life it should be charged to about 4V/cell. This
corresponds to about 70% charge. Above this voltage the anode degrades.
Below this voltage and the cathode degrades (so I'm told).
If you have control of the inner workings of the charger you could
try resetting the voltage to ~4V/cell (4V ?) and just leave it plugged in.
RP

Post by James Cameron
In my experience it depends on the phone DC input, usually under
firmware control.
Measure current over time on the DC input to document behaviour.
Some phones reach charged state and disconnect the DC input, then
draw almost no current until either battery voltage falls, or
estimated state of charge falls below something like 90% or 95%,
then they reconnect until charged.
Some phones reach charged state and disconnect the battery,
operating from the DC input until the DC input is removed. Of
these, some won't track estimated state of charge during the
self-discharge phase, and some will.
One device I have goes one step further; if you leave it connected
for a week, it presumes you plan to leave it connected forever, and
says so; it disconnects the DC input until estimated state of
charge reaches 50%, then transfers the load to the DC input.
Thus it entirely defeats the idea of keeping the device _ready_ for
use on battery in this way.
--
James Cameron
http://quozl.netrek.org/
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at http://mailman.mit.edu/
mailman/listinfo/piclist
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist

[RussellMc]

On 31 May 2018 at 08:26, Van Horn, David <

Post by Van Horn, David
When I was designing NIMH chargers on the AVR, this was one of my go-to sources.
Tempered by the data sheet of the specific cells we were using.
NIMH is a real pain to charge correctly especially if your charger has to
operate in other than shirtsleeve temperatures.
​And, when also

the ambient temperature is sun variable, slugged by thermal mass,
the energy input is ​sun variable - and affected by clouds, children, and
time of day,
and the batteries may be heated to above their rated max charging
temperature, or not ... .
Agh!


R