Lithium ion battery problem

Thread Starter

psoke0

Joined Mar 31, 2017
121
hey guys. i just charged my liIon battery and its charged to 4,2 volt blue light come on . i checked the voltahe it was 4,2 volts and when i dis connected the battery it drop to 4,01 and stayed there what is happening. is it because its lost some of its capacity in time or what why is it doing that my other battery doesnt o that its just stays at 4,2 v even when its not connected to anything (charger etc.) i mean does open curcuit voltage of liIon battery drops even fully charged when its ages and lost its capacity? please answer me thank you.
 
Last edited:

Audioguru again

Joined Oct 21, 2019
1,908
Your charger circuit is too simple. When a lithium battery cell reaches 4.2V then it is only partially charged. It is full charged when its voltage is 4.2V AND its charging current drips to a low amount.

Since one battery works fine then the battery that drops its voltage is worn out and needs replacing.
 

KeithWalker

Joined Jul 10, 2017
1,216
There is nothing wrong with that battery.
A lithium ion battery charger terminates the charge when the terminal voltage reaches 4.2V and the current falls to 1/10 the full charging current. If current can still flow from the charger to the battery, it means that internally, the battery voltage must be less than 4.2V or there would be no current flow. That is the terminal voltage that you see when you disconnect the charger.
If you have a battery that measures the same when connected to the charger and when disconnected, it is either over charged or has unusually low internal resistance.
Regards,
Keith
charge.jpg
 

Thread Starter

psoke0

Joined Mar 31, 2017
121
but does internal resistance effects open curcuit measurement of battery ? and i have another question the tp4056 module tries to charge it firs with constant current of 1 Amp but when i measure the voltage of battery it is 3,9 and charge current is not 1 amp its about 330 mA . so does internal resistance cousing the charges to fail to charge it with constant current of 1 amp ?
 
Last edited:

Audioguru again

Joined Oct 21, 2019
1,908
My newest Li-PO batteries are 2 years old and have been charged and discharged hundreds of times. I fully charged them 2 weeks ago. One is still at 4.2V per cell and one has its voltage reduced to 4.15V per cell.

One Li-PO battery is 5 years old, has had maybe one thousand charge-discharge cycles, was fully charged to 4.2V per cell a few weeks ago and measures 4.12V per cell.

My Li-PO batteries last for a long time and for many cycles because I store them at 3.7V per cell each winter.
 
Last edited:

KeithWalker

Joined Jul 10, 2017
1,216
but does internal resistance effects open curcuit measurement of battery ? and i have another question the tp4056 module tries to charge it firs with constant current of 1 Amp but when i measure the voltage of battery it is 3,9 and charge current is not 1 amp its about 330 mA . so does internal resistance cousing the charges to fail to charge it with constant current of 1 amp ?
Your first question:
The amount by which the internal resistance of the battery will effect the terminal voltage measurement of the battery will depend on how much current will flow through the meter. Digital multimeters have an extremely high input resistance, so the current will only be microamps and the effect will be negligible.
Your second question:
I don't know any details of the design of your charger so I cannot comment on how much charging current it will supply. How did you measure the charge current? If you put an ammeter in series with the battery and charger, you increased the resistance in the charging circuit, That would change the effective terminal voltage of the battery as seen by the charger and could effect the charge current.
Regards,
Keith
 

Thread Starter

psoke0

Joined Mar 31, 2017
121
Your first question:
The amount by which the internal resistance of the battery will effect the terminal voltage measurement of the battery will depend on how much current will flow through the meter. Digital multimeters have an extremely high input resistance, so the current will only be microamps and the effect will be negligible.
Your second question:
I don't know any details of the design of your charger so I cannot comment on how much charging current it will supply. How did you measure the charge current? If you put an ammeter in series with the battery and charger, you increased the resistance in the charging circuit, That would change the effective terminal voltage of the battery as seen by the charger and could effect the charge current.
Regards,
Keith
so instead of putting multimeter in series we should use known shunt and measure voltage across it ?
 

Thread Starter

psoke0

Joined Mar 31, 2017
121
Your first question:
The amount by which the internal resistance of the battery will effect the terminal voltage measurement of the battery will depend on how much current will flow through the meter. Digital multimeters have an extremely high input resistance, so the current will only be microamps and the effect will be negligible.
Your second question:
I don't know any details of the design of your charger so I cannot comment on how much charging current it will supply. How did you measure the charge current? If you put an ammeter in series with the battery and charger, you increased the resistance in the charging circuit, That would change the effective terminal voltage of the battery as seen by the charger and could effect the charge current.
Regards,
Keith
i have another question and thank you so much for answering them. i have a battery that have 144 mOhm internal resistance. but its get hot when chrging and even 600 mA goin throu it it doesnt rise the voltage up . des that men its have high self discharge ?
 

Audioguru again

Joined Oct 21, 2019
1,908
If a lithium battery gets hot when charging with the recommended voltage and current then it is defective and could explode/catch on fire at any time. Dispose it safely.

If a Lithium battery cell has been discharged below about 3V then it is damaged and could cause your overheat/explosion/fire problem.
 

Thread Starter

psoke0

Joined Mar 31, 2017
121
If a lithium battery gets hot when charging with the recommended voltage and current then it is defective and could explode/catch on fire at any time. Dispose it safely.

If a Lithium battery cell has been discharged below about 3V then it is damaged and could cause your overheat/explosion/fire problem.
thank you
 

KeithWalker

Joined Jul 10, 2017
1,216
i have another question and thank you so much for answering them. i have a battery that have 144 mOhm internal resistance. but its get hot when chrging and even 600 mA goin throu it it doesnt rise the voltage up . des that men its have high self discharge ?
The internal resistance of a Li-Po battery is in the order of 10 to 30 mOhms depending on it's capacity and age. The battery that has 144 mOhms internal resistance has probably been discharged below the minimum voltage of 2,7V and is past the end of it's useful life.It
Keith
 

Thread Starter

psoke0

Joined Mar 31, 2017
121
The internal resistance of a Li-Po battery is in the order of 10 to 30 mOhms depending on it's capacity and age. The battery that has 144 mOhms internal resistance has probably been discharged below the minimum voltage of 2,7V and is past the end of it's useful life.It
Keith
its lithium ion battery this battery didnt go below 2,7 volts
 

Audioguru again

Joined Oct 21, 2019
1,908
A Li-PO has the same chemistry and spec's as a Li-Ion.
Horizon Hobby says when the voltage goes below 3.2V then its charge is gone and damage begins.
I say to avoid going below 3V and some Chinese people say 2.7V.
 

KeithWalker

Joined Jul 10, 2017
1,216
I got the figure of 2.7V directly from the engineer at Spar Aerospace who was building battery packs for satellites. I designed a test system for them back in the nineties. His very words were "If you let them go below 2.7 volts you have just made some very expensive book ends.
Regards,
Keith
 

Thread Starter

psoke0

Joined Mar 31, 2017
121
A Li-PO has the same chemistry and spec's as a Li-Ion.
Horizon Hobby says when the voltage goes below 3.2V then its charge is gone and damage begins.
I say to avoid going below 3V and some Chinese people say 2.7V.
I got the figure of 2.7V directly from the engineer at Spar Aerospace who was building battery packs for satellites. I designed a test system for them back in the nineties. His very words were "If you let them go below 2.7 volts you have just made some very expensive book ends.
Regards,
Keith
thank you guys
 
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