Hello! Thank you a lot for your video. I just started working on Batteries and I was trying to build a CCCV model on Simulink, I do have a battery pack with 192 nom.V. They are connected in series and in parallel. So I was wondering about how can I build a model. I wanted to charge with const current until I reach my 192 V and switch to a const v charger. I might be mistaken, If you are still available to give some feedbacks, I could share with my Simulink model.
Hello I'm really sorry for the delay of my feedback. I am not an expert in battery simulation, but i have found these articles that perhaps could help you: H.J. Bergveld, W.S. Kruijt, P.H.L. Notten, “Battery Management Systems, Design by Modeling”, Kluwer Academic Publishers, 2002. M. Dubarry, B.Y. Liaw, “Development of a universal modelling tool for rechargeable lithium batteries”, Journal of Power Sources, Volume 174 (2007), Issue 2, 856-860. Hope it helps
You mean how we determine that it is 4.2V ? That value is given by the manufacturer and is based on the battery chemistry. For classic Lithium battery, the maximum charge voltage for which you transit from CC to CV is generally 4.2V but you can find some manufacturer that advises you to set that value at 4.1V or even 4V. It increases a bit the lifespan of your battery by a higher endurance cycle, but you lose a bit in capacity. It's like a car: say the manufacturer of your car tells you you can drive up to 150 mph. For sure you understand that if you drive all your life at that speed, the engine will last less than if you drived at a lower pace, say 100 mph.
@@ramayanamsanthosh7326 No, 4.2V is what is called the battery's End of Charge voltage (EoC), a voltage the battery manufacturer recommend to not go beyond to avoid damaging his battery. Note: here i use 4.2V, but it can be 4.1V or other values, it depends of the manufacturer and what he considered as safe and good to respect the lifetime and number of cycle he promised in his datasheet.
It is possible but only if you do not go over Vcharge max, and that you don't go over the maximum current that the battery can withstand continuously during the charging stage. Because of that, your limit on your constant Power setting (current x voltage) on the full battery charging voltage sweep (Vmin to Vmax) is given by Plimit = current max x Vmin Second point, your charging system will adjust constantly the current while monitoring the voltage to ensure a constant power (current x voltage). When the voltage monitored reaches the Vmax, you can't continue in constant power mode, you then simply have to switch to constant voltage mode.
Hi Julien, I have a Li-ion battery and I want to charge a cell with a power supply. I have been reading about the CC-CV charging method and everywhere it is said to set the voltage upper limit to 4.2V and to limit the current to around 1C (in my case, it is 7Ah). The first time, I started charging the cell when its voltage was 3.8V but the current that flows from the power supply to the cell was only 1.3A (I have set the max limit of the current to 6A) and I do not understand why it is so small (the value of the internal resistance of the cell that appears on the datasheet is around 1mOhm) so I do not know if I should increase the upper limit of the voltage during the CC phase (maintaining the limit of hte current on 6A) till the current reaches 6A and setting it to 4.2V when the cell reaches this value of voltage (when changing to the CV phase) or it could be dangerous for the cell. Thank you very much.
Hello Daniel, Which power supply unit are you using? If you have possibility to set both current and voltage limit, if you set: Vlimit = 4.2V Ilimit = 6Amps The power supply will naturally go to one of the mode: voltage source or current source. When you had that current lower than 6 Amps, what was the voltage limit that you set? Normally your system would have been here in voltage source mode. By the way, never put a voltage limit higher than 4.2V or other value that the Li Ion supplier would recommend. Other thing: some power supply vendor give you possibility to set voltage or current protection value. These are a bit different than voltage or current setting in the sense that IF your system reach that value, the power supply immediately disconnect the power supply. Of course, V and I safety setting are always a bit higher or lower than your settings to not stop unwillingly the charging or discharging process (discharging for load source which are a kind a power supply that can absorb power) .
What do you mean by : " how you set this current". Do you mean why this number? Or do you mean how we stop experimentally at this number. For the first, this 0.03C is totally arbitrary and will depend on the manufacturer or even yourself. All manufacturer, when they give you a capacity, they have also to tell you the way they achieved that capacity, this is where you will find those indication of charging terminiation. For the percentage of current compared to C, the lower the percentage is, the longer it will take you to reach the termination condition. It does not worth to go very low, 10% is normally large enough. Going further below will greatky increase your time of fully charging but a very little gain of capacity. Please note you have also the possibility to decide of the termination of the charging not by a value on the current, but by a time after you entered into the CV mode, say for example 1 hour. But it implies that during this time, the battery continues to charge at the same pace and is not perturbed by a load asking for some current. Now if your question was related to how experimentally we stop a 0.03%, 2 solutions: - You buy a dedicated Lithium charging chip, and they have for most of them a configuration pin to define the termination current (generally a simple resistor setting. - You do your own circuit, then you need to measure the current, shunt resistor circuit for example, that will give you a voltage reading of the current. You can either make an analog circuit to stop the charging (comparator with hysteresis + load switch) or make a ADC reading to an MCU that will stop the charging through the control of the switch (i prefer that option as you can easily change the termination current setting through the program).
thank you sir.please answer me if i takes this cell(3.3V)and make a battery with 330 V how i can take the maximum voltage protection.in your case is 4.2V it is (4.2*100) in my case,,?
Hello, May i know the reference of the cell? Can you confirm me it is a secondary cell type? 3.3V is your nominal voltage per cell? Take note that for such serial assembly, you have to deal with battery balancing technique to make sure all cells arrive to their limits in coordination.
Hi sorry if this is a silly question - How does the current from the supply stay at a constant rate while the voltage increases? I thought the current decreases when the battery state of charge is nearing 100%?
There is no silly question, if you ask it is because my video is not clear enough. The current remains constant because the power supply settings is set on constant current mode in the first stage of the charging protocol, until it reaches the targeted voltage of the battery and enter into the constant voltage mode. Everything is about a regulation of the power supply itself, a regultation on current or on the voltage, by means of electronic self counter reaction. Why? There are two things you have to respect while charging a Lithium ion battery: you must not go beyond a limit of current and a limit of voltage otherwise you will damage the battery. Say your battery high voltage limit is 4.2V and current limit is 1 amp. When your battery is given to you discharged, say you measure 3V with your multimeter. Now you want to charge it with your power supply. On a power supply you can set a limit in the current and in the voltage. Set these limits to your power supply (4.2V and 1 amp). On the beginning, your power supply will be limited by the currrent limit. Why? because battery's voltage is 3V and if you try to apply 4.2 V on it you would have a huge current because of the low battery's internal resistance. Example: say this resistance is 0.1 Ohm, Ohm's law tells you that current should be: (4.2 - 3)/0.1 = 12 amps. This 12 amps are far above the limit of 1 amp, so the power supply do a counter reaction that locks the power supply on a voltage that would give 1amp. So you are in a constant current mode in the beginning. Now internally, some chemical process occurs inside the battery and its voltage increase slowly and have this shape you see on the graph. When the power supply reaches 4.2 V, the internal circuitry detects that it is your maximum value not to go above, and then it automatically reduces the current to respect the instruction (which is dont go above 4.2V). You are now in the constant voltage mode. On your graph you will see slowly the current decreasing to respect this instruction. You can stop the charging after it reaches a current threshold (typically between 3% and 10% of your current target, that is to say here 30 milliamp to 100 milliamp). Your battery is charged. Is it clearer for you? we can talk further if you want in private.
@@nainabla that is correct. When you have achieved your Constant Current stage (CC part of a CC/CV protocol), you have roughly charged 70-80% of the rated capacity, and to get the 20-30% remaining in the Constant Voltage stage, it will take you far more time. This is on that aspect of difference of capacity gain versus time between these 2 stages, that most of the "fast" charger are based on (at least their marketing speech do not tell you explicitly that the trick is in fact easy to understand, and no magic is behind).
@@nainabla the charger knows it because it is him who deals with the CC/CV protocol. It is him who provides current and senses the battery's voltage increasing during the Constant Current stage (during that stage there is a feedback control loop mechanism in which the charger plays with the voltage to maintain the fixed targeteg current). It is the charger who then changes its regulation mode from constant current to constant voltage when battery's voltage reaches the 4.2V for a single Li-ion battery (can be 4.1V, depends on what the manufacturer recommends). In that stage, still we have a feedback control loop mechanism where the system does all he can to maintain the targeted voltage by playing on the current. The charger can have feature in which he tells you that he has reached the transition between CC and CV, and you know from the battery datasheet (at least for most of them) that you already have then reached 70 to 80% of the rated capacity. To reach 100%, you need to configure your charger in the same way that the battery describes it. There are few parameters to take into account: - during the charging, the parameters are the charging current, the end of charge voltage (the say 4.2V), and the termination of charge current (a fixed value given in fraction of capacity, typically C/10). - During the discharge, the parameters are the discharging current (typically C/5) and the end of discharge voltage (typically 3V). If you follow those instructions, then the manufacturer "guarantee" you the rated capacity. If you change some of the parameters at least inside the voltage and current recommended operating specs, you may find a higher or lower capacity. Is that clear?
Hi sir, If the CC value is from C/5 to 1C and the initial voltage and max. voltage is remaining the same. What will the current curve & voltage curve like?. Thanks
Hi, I don't understand your question. Can you develop further? What do you mean by the initial voltage and max voltage remains the same for example? Thanks
@@julienc.4916 I mean based on your uploaded video, where the starting constant current is C/5 and you build the current curve and the voltage curve. My question is: If the starting constant current is not C/5 but it is 1C and the initial & max. voltage are the same, what will the current and volatge curve be?
@@cheungkimwai1919 Okay understood. Very good question. Typically the voltage curve will be steeper on the Constant Current phase, so the Constant Voltage phase will be reached in a shorter time. But once you are in the Constant Voltage phase, I am not sure. I have done the tests years ago but i don't remember. Instinctively i would say the current curve should be stretched further and be less steep. That's a good experiment to do actually.
Thanks :) The charging/discharging process type is used accordingly to a battery chemistry and is not related to the power size. What will change is the voltage and current limits based on the assembly configuration of the battery (battery = assembly of minimum 1 cell in series and/or parallel). For large power that you can meet for example in a charger for a EV, the BMS (Battery Management System) is sized to handle huge power, and distribute it efficiently to a set of batteries containing thousands of individual Li-Ion cells assembled in parallel and series.
@@julienc.4916 thank you for the fast response. In large-scale battery (range of MW) for applications in power systems, it is said that the battery can instantaneously (almost; in the range of miliseconds) change from absorbing mode to injection mode (absorbing or injecting power to the grid). How can this be so fast if the charging process that you showed must follow all of the appropriate steps? This is the part I don't quite understand. And in the large-scale battery, the value of the power being absorbed/injected can be controlled to any specific value. How can this be achieved without violating the specifications of the charging process tha you showed? Thank you again.
@@jasdfff770 Good question. The video I show is just about a full charging process that is not interrupted by a discharge. In real applications, like your cellphone, you can absolutely charge your phone, and remove the USB charger to watch a youtube video that is power-hungry, meaning you discharge it, and then a few minutes after you put it back to charge. That is just an example but there is no problem switching from charging to discharging mode in a random manner, simply when you will go back to your charging stage, the BMS will apply its CC/CV protocol without taking care of what happened before. He will apply first a current regulation, and if the end voltage limit is already reached, he will simply hold therefore to voltage regulation.
During the CV phase of charging, an exponentially falling current is still going inside the battery so why doesn't the voltage across battery increase in that phase?
Once you reach the voltage that you claim it is your target value to maintain during the CV stage, either you use a specialized circuit or use your lab power supply configured in voltage mode. The voltage mode is simple to understand: by an algorithm type loop or feedback, do (the IC or the power lab supply) whatever you can to maintain the voltage targetted, by regulating the delivered current. It is the internal Physico-chemical reaction that occurs during the CV charging process that leads to this current shape of an exponentially falling curve while you enter into the CV stage. Many electronic/physics/chemical models offer their own explanations of the real process occurring, this one having many parameters in the model, such as the temperature, the chemistry of your cell, the rate of reaction etc. I hope my answer help you a little, if not please continue asking more question, I'd be happy to help.
www.ti.com/lit/ds/symlink/lm317.pdf See figure 8.3.6 Please see also video from Dave Jones regarding Lab Power Supply. Below part 1 link, see the others as well: ruclips.net/video/CIGjActDeoM/видео.html
Hello, Below multiple image so perhaps you can better understand: When charging an empty battery, you displace in opposite direction charged particles, positive and negative, from one electrode of the battery to another. A bit like when you pump water from the bottom of a river dam to its top in order to recharge the reservoir. To displace that water you need some "force", moving up the water of a certain "height". In your battery this "force" comes from an electrical field applied by your power generator. The height of the river dam represent your voltage. Charging a battery is like filling up a river dam: if you fill up too much you can have issues. We can't speak of advantage or disadvantage of moving to CV mode cause moving to CV mode is done naturally by your power regulator when you reach the maximum voltage recommended. Why the current is decreasing this way once reaching the CV mode? Other image to help you: for a given force, it comes more and more difficult to the power regulator to move positive and negative charge from one electrode to the other. A bit like when you fill up a balloon: in the beginning with a fixed volume of air per second that you inflate, you will find it easy. Once you reach the stretching limit of the baloon, if you keep inflating with the same force, you'll see that the volume of air per second passing is reducing cause you are in opposition with the pression of the balloon itself which applies a higher pressure in return equilibrating with yours for a lower flow. Of course you'll understand that if you don't like the air flow to reduce, you can increase the pression of air flow by your mouth (voltage applied) and you"ll see the ballon stretching until it explodes. Hope that helps you
Also, once in CV mode, you have normally charged the battery for 70 to 80% of its capacity. Going into the CV mode will charge the remaining 20 to 30% but it will take you a longer time, actually the closer you get to the 100% capacity the longer it will take you. Some charger who says they charge ultra fast is because they don't go into the CV mode.
@@julienc.4916 I agree with u sir, what u have explained is absolutely correct but there is a slight change. That lithium ion or polymer battery never be charged to 100% bcz of voltage stress problem so, it's advisable to charge below 100%.
@@raviteja-bn2eg It is a bit more complex than that. In fact to say a battery is 100% charged is a convention based on a protocol of charge and discharge given by the battery manufacturer and for which he guarantee a certain capacity. This protocol is a CC/CV with a charging stage and a discharging stage. Typical example of a protocol used to define capacity based on the IEC 61960 standard: For the charging stage: - Charge at 0.2C for the CC stage, - Transfer to CV mode once 4.2V reached, and stop the charge once you reach current defined by a fraction of C, or stop after a defined period of time, typically 1 hour. For the discharge stage, this one is used to calculate your capacity: - 0.2C discharge current, - End of discharge at 3V. Capacity is simply given by the expression: C (mAh) = discharge time (hours) x discharge current (mA) You can find these information by reading the IEC 61960 standard. When i say it is a convention, a battery manufacturer can decide to use its own CC/CV protocol, which can be more favorable to battery life, but will gove less capacity (you can't have all). It is better for example to define your CV charging stage at 4.1V instead of 4.2V for Li ion battery, as it will give less stress and give you higher cycle. But as i said, you'll have a bit less capacity.
hi sir, i want to know when we charge battery in CV mode the current gets decreases slowly. but my question is that how they set the stop current for charging. is there any standard aboyt this
Dear Harshal Sable there is no general rule on that question. It depends. Some manufacturer will tell you 0.03 C, some 0.1 C. The smaller you set, a little bigger capacity you will get but not so much. And it will take you also more and more time as you tend to 0 C (until infinity in theory). Regarding existing standard, please refer to the IEC 61960. If my memory is good, they don't give a end of charge rule based on a value of the current in CV mode, but on a time basis. They say that your charge is finished one hour after you entered into the CV mode. It is up to you, but that may be a good start that you use this rule.
this is a fantastic explenation. you are simply amazing.
Thank you sir, i feel honored by the compliment.
Hello! Thank you a lot for your video. I just started working on Batteries and I was trying to build a CCCV model on Simulink, I do have a battery pack with 192 nom.V. They are connected in series and in parallel. So I was wondering about how can I build a model. I wanted to charge with const current until I reach my 192 V and switch to a const v charger. I might be mistaken, If you are still available to give some feedbacks, I could share with my Simulink model.
Hello
I'm really sorry for the delay of my feedback. I am not an expert in battery simulation, but i have found these articles that perhaps could help you:
H.J. Bergveld, W.S. Kruijt, P.H.L. Notten, “Battery Management Systems,
Design by Modeling”, Kluwer Academic Publishers, 2002.
M. Dubarry, B.Y. Liaw, “Development of a universal modelling tool for
rechargeable lithium batteries”, Journal of Power Sources, Volume 174 (2007),
Issue 2, 856-860.
Hope it helps
@@julienc.4916 Thats so nice of you. Thank you so much!!!!🤗
@@aidazhanybekkyzy1264 You are welcome. Just a question: are you trying to simulate a model of the battery itself, or the charger?
@@julienc.4916 I was simulating my battery itself, as a charger I took constant current and voltage source.
@@aidazhanybekkyzy1264 Ok, them yes you can look into the articles i sent you. Good luck!
how did you determine the reference voltage to transit from CC to CV?
You mean how we determine that it is 4.2V ? That value is given by the manufacturer and is based on the battery chemistry. For classic Lithium battery, the maximum charge voltage for which you transit from CC to CV is generally 4.2V but you can find some manufacturer that advises you to set that value at 4.1V or even 4V. It increases a bit the lifespan of your battery by a higher endurance cycle, but you lose a bit in capacity. It's like a car: say the manufacturer of your car tells you you can drive up to 150 mph. For sure you understand that if you drive all your life at that speed, the engine will last less than if you drived at a lower pace, say 100 mph.
@@julienc.4916 is 4.2 is the boost voltage of the battery?
@@ramayanamsanthosh7326
No, 4.2V is what is called the battery's End of Charge voltage (EoC), a voltage the battery manufacturer recommend to not go beyond to avoid damaging his battery. Note: here i use 4.2V, but it can be 4.1V or other values, it depends of the manufacturer and what he considered as safe and good to respect the lifetime and number of cycle he promised in his datasheet.
Can we use constant power mode for changing？
It is possible but only if you do not go over Vcharge max, and that you don't go over the maximum current that the battery can withstand continuously during the charging stage. Because of that, your limit on your constant Power setting (current x voltage) on the full battery charging voltage sweep (Vmin to Vmax) is given by Plimit = current max x Vmin
Second point, your charging system will adjust constantly the current while monitoring the voltage to ensure a constant power (current x voltage).
When the voltage monitored reaches the Vmax, you can't continue in constant power mode, you then simply have to switch to constant voltage mode.
Hi Julien,
I have a Li-ion battery and I want to charge a cell with a power supply. I have been reading about the CC-CV charging method and everywhere it is said to set the voltage upper limit to 4.2V and to limit the current to around 1C (in my case, it is 7Ah).
The first time, I started charging the cell when its voltage was 3.8V but the current that flows from the power supply to the cell was only 1.3A (I have set the max limit of the current to 6A) and I do not understand why it is so small (the value of the internal resistance of the cell that appears on the datasheet is around 1mOhm) so I do not know if I should increase the upper limit of the voltage during the CC phase (maintaining the limit of hte current on 6A) till the current reaches 6A and setting it to 4.2V when the cell reaches this value of voltage (when changing to the CV phase) or it could be dangerous for the cell.
Thank you very much.
Hello Daniel,
Which power supply unit are you using?
If you have possibility to set both current and voltage limit, if you set:
Vlimit = 4.2V
Ilimit = 6Amps
The power supply will naturally go to one of the mode: voltage source or current source.
When you had that current lower than 6 Amps, what was the voltage limit that you set? Normally your system would have been here in voltage source mode.
By the way, never put a voltage limit higher than 4.2V or other value that the Li Ion supplier would recommend.
Other thing: some power supply vendor give you possibility to set voltage or current protection value. These are a bit different than voltage or current setting in the sense that IF your system reach that value, the power supply immediately disconnect the power supply.
Of course, V and I safety setting are always a bit higher or lower than your settings to not stop unwillingly the charging or discharging process (discharging for load source which are a kind a power supply that can absorb power) .
in this case, in cv mode you stop charging when the current falls down to 0.03C.
how you set this current
What do you mean by : " how you set this current". Do you mean why this number? Or do you mean how we stop experimentally at this number.
For the first, this 0.03C is totally arbitrary and will depend on the manufacturer or even yourself. All manufacturer, when they give you a capacity, they have also to tell you the way they achieved that capacity, this is where you will find those indication of charging terminiation. For the percentage of current compared to C, the lower the percentage is, the longer it will take you to reach the termination condition. It does not worth to go very low, 10% is normally large enough. Going further below will greatky increase your time of fully charging but a very little gain of capacity. Please note you have also the possibility to decide of the termination of the charging not by a value on the current, but by a time after you entered into the CV mode, say for example 1 hour. But it implies that during this time, the battery continues to charge at the same pace and is not perturbed by a load asking for some current.
Now if your question was related to how experimentally we stop a 0.03%, 2 solutions:
- You buy a dedicated Lithium charging chip, and they have for most of them a configuration pin to define the termination current (generally a simple resistor setting.
- You do your own circuit, then you need to measure the current, shunt resistor circuit for example, that will give you a voltage reading of the current. You can either make an analog circuit to stop the charging (comparator with hysteresis + load switch) or make a ADC reading to an MCU that will stop the charging through the control of the switch (i prefer that option as you can easily change the termination current setting through the program).
thank you sir.please answer me if i takes this cell(3.3V)and make a battery with 330 V how i can take the maximum voltage protection.in your case is 4.2V it is (4.2*100) in my case,,?
Hello,
May i know the reference of the cell? Can you confirm me it is a secondary cell type?
3.3V is your nominal voltage per cell?
Take note that for such serial assembly, you have to deal with battery balancing technique to make sure all cells arrive to their limits in coordination.
So it's a matter of pressure in regulation . I'm going to look and see if analog and plasma might be better in some applications . Thank You
Hi sorry if this is a silly question - How does the current from the supply stay at a constant rate while the voltage increases? I thought the current decreases when the battery state of charge is nearing 100%?
There is no silly question, if you ask it is because my video is not clear enough.
The current remains constant because the power supply settings is set on constant current mode in the first stage of the charging protocol, until it reaches the targeted voltage of the battery and enter into the constant voltage mode. Everything is about a regulation of the power supply itself, a regultation on current or on the voltage, by means of electronic self counter reaction.
Why? There are two things you have to respect while charging a Lithium ion battery: you must not go beyond a limit of current and a limit of voltage otherwise you will damage the battery. Say your battery high voltage limit is 4.2V and current limit is 1 amp. When your battery is given to you discharged, say you measure 3V with your multimeter. Now you want to charge it with your power supply. On a power supply you can set a limit in the current and in the voltage. Set these limits to your power supply (4.2V and 1 amp). On the beginning, your power supply will be limited by the currrent limit. Why? because battery's voltage is 3V and if you try to apply 4.2 V on it you would have a huge current because of the low battery's internal resistance. Example: say this resistance is 0.1 Ohm, Ohm's law tells you that current should be: (4.2 - 3)/0.1 = 12 amps.
This 12 amps are far above the limit of 1 amp, so the power supply do a counter reaction that locks the power supply on a voltage that would give 1amp. So you are in a constant current mode in the beginning. Now internally, some chemical process occurs inside the battery and its voltage increase slowly and have this shape you see on the graph. When the power supply reaches 4.2 V, the internal circuitry detects that it is your maximum value not to go above, and then it automatically reduces the current to respect the instruction (which is dont go above 4.2V). You are now in the constant voltage mode. On your graph you will see slowly the current decreasing to respect this instruction. You can stop the charging after it reaches a current threshold (typically between 3% and 10% of your current target, that is to say here 30 milliamp to 100 milliamp). Your battery is charged.
Is it clearer for you? we can talk further if you want in private.
@@julienc.4916 So if i understand correctly, the battery voltage at 70-80% is 4.2V ?
@@nainabla that is correct. When you have achieved your Constant Current stage (CC part of a CC/CV protocol), you have roughly charged 70-80% of the rated capacity, and to get the 20-30% remaining in the Constant Voltage stage, it will take you far more time. This is on that aspect of difference of capacity gain versus time between these 2 stages, that most of the "fast" charger are based on (at least their marketing speech do not tell you explicitly that the trick is in fact easy to understand, and no magic is behind).
@@julienc.4916 but how does the charger know when the battery is full if the battery is at the same voltage at 70% and 100%.
@@nainabla the charger knows it because it is him who deals with the CC/CV protocol.
It is him who provides current and senses the battery's voltage increasing during the Constant Current stage (during that stage there is a feedback control loop mechanism in which the charger plays with the voltage to maintain the fixed targeteg current). It is the charger who then changes its regulation mode from constant current to constant voltage when battery's voltage reaches the 4.2V for a single Li-ion battery (can be 4.1V, depends on what the manufacturer recommends). In that stage, still we have a feedback control loop mechanism where the system does all he can to maintain the targeted voltage by playing on the current.
The charger can have feature in which he tells you that he has reached the transition between CC and CV, and you know from the battery datasheet (at least for most of them) that you already have then reached 70 to 80% of the rated capacity.
To reach 100%, you need to configure your charger in the same way that the battery describes it. There are few parameters to take into account:
- during the charging, the parameters are the charging current, the end of charge voltage (the say 4.2V), and the termination of charge current (a fixed value given in fraction of capacity, typically C/10).
- During the discharge, the parameters are the discharging current (typically C/5) and the end of discharge voltage (typically 3V).
If you follow those instructions, then the manufacturer "guarantee" you the rated capacity. If you change some of the parameters at least inside the voltage and current recommended operating specs, you may find a higher or lower capacity.
Is that clear?
Hi sir,
If the CC value is from C/5 to 1C and the initial voltage and max. voltage is remaining the same. What will the current curve & voltage curve like?.
Thanks
Hi, I don't understand your question. Can you develop further? What do you mean by the initial voltage and max voltage remains the same for example? Thanks
@@julienc.4916 I mean based on your uploaded video, where the starting constant current is C/5 and you build the current curve and the voltage curve.
My question is:
If the starting constant current is not C/5 but it is 1C and the initial & max. voltage are the same, what will the current and volatge curve be?
I mean the initial voltage & max. voltage are same as your example.
@@cheungkimwai1919 Okay understood. Very good question. Typically the voltage curve will be steeper on the Constant Current phase, so the Constant Voltage phase will be reached in a shorter time. But once you are in the Constant Voltage phase, I am not sure. I have done the tests years ago but i don't remember. Instinctively i would say the current curve should be stretched further and be less steep. That's a good experiment to do actually.
Nice video!!
Question: Does this charging process also apply to large-scale battery (power grid application, in the range of kW to MW)?
Thanks :)
The charging/discharging process type is used accordingly to a battery chemistry and is not related to the power size. What will change is the voltage and current limits based on the assembly configuration of the battery (battery = assembly of minimum 1 cell in series and/or parallel).
For large power that you can meet for example in a charger for a EV, the BMS (Battery Management System) is sized to handle huge power, and distribute it efficiently to a set of batteries containing thousands of individual Li-Ion cells assembled in parallel and series.
@@julienc.4916 thank you for the fast response.
In large-scale battery (range of MW) for applications in power systems, it is said that the battery can instantaneously (almost; in the range of miliseconds) change from absorbing mode to injection mode (absorbing or injecting power to the grid). How can this be so fast if the charging process that you showed must follow all of the appropriate steps? This is the part I don't quite understand. And in the large-scale battery, the value of the power being absorbed/injected can be controlled to any specific value. How can this be achieved without violating the specifications of the charging process tha you showed? Thank you again.
@@jasdfff770 Good question. The video I show is just about a full charging process that is not interrupted by a discharge. In real applications, like your cellphone, you can absolutely charge your phone, and remove the USB charger to watch a youtube video that is power-hungry, meaning you discharge it, and then a few minutes after you put it back to charge. That is just an example but there is no problem switching from charging to discharging mode in a random manner, simply when you will go back to your charging stage, the BMS will apply its CC/CV protocol without taking care of what happened before. He will apply first a current regulation, and if the end voltage limit is already reached, he will simply hold therefore to voltage regulation.
During the CV phase of charging, an exponentially falling current is still going inside the battery so why doesn't the voltage across battery increase in that phase?
Once you reach the voltage that you claim it is your target value to maintain during the CV stage, either you use a specialized circuit or use your lab power supply configured in voltage mode. The voltage mode is simple to understand: by an algorithm type loop or feedback, do (the IC or the power lab supply) whatever you can to maintain the voltage targetted, by regulating the delivered current.
It is the internal Physico-chemical reaction that occurs during the CV charging process that leads to this current shape of an exponentially falling curve while you enter into the CV stage. Many electronic/physics/chemical models offer their own explanations of the real process occurring, this one having many parameters in the model, such as the temperature, the chemistry of your cell, the rate of reaction etc.
I hope my answer help you a little, if not please continue asking more question, I'd be happy to help.
Can you share a source that will help me understand the control technique used in the CCCV charger?
www.ti.com/lit/ds/symlink/lm317.pdf
See figure 8.3.6
Please see also video from Dave Jones regarding Lab Power Supply. Below part 1 link, see the others as well:
ruclips.net/video/CIGjActDeoM/видео.html
thanks for the help, much appreciated :)
hello sir,
what are the major advantages in shifting to CV mode?
why current is exponentially decreasing in case of CV mode?
Hello,
Below multiple image so perhaps you can better understand:
When charging an empty battery, you displace in opposite direction charged particles, positive and negative, from one electrode of the battery to another. A bit like when you pump water from the bottom of a river dam to its top in order to recharge the reservoir. To displace that water you need some "force", moving up the water of a certain "height". In your battery this "force" comes from an electrical field applied by your power generator. The height of the river dam represent your voltage.
Charging a battery is like filling up a river dam: if you fill up too much you can have issues.
We can't speak of advantage or disadvantage of moving to CV mode cause moving to CV mode is done naturally by your power regulator when you reach the maximum voltage recommended.
Why the current is decreasing this way once reaching the CV mode?
Other image to help you: for a given force, it comes more and more difficult to the power regulator to move positive and negative charge from one electrode to the other. A bit like when you fill up a balloon: in the beginning with a fixed volume of air per second that you inflate, you will find it easy. Once you reach the stretching limit of the baloon, if you keep inflating with the same force, you'll see that the volume of air per second passing is reducing cause you are in opposition with the pression of the balloon itself which applies a higher pressure in return equilibrating with yours for a lower flow. Of course you'll understand that if you don't like the air flow to reduce, you can increase the pression of air flow by your mouth (voltage applied) and you"ll see the ballon stretching until it explodes.
Hope that helps you
Also, once in CV mode, you have normally charged the battery for 70 to 80% of its capacity. Going into the CV mode will charge the remaining 20 to 30% but it will take you a longer time, actually the closer you get to the 100% capacity the longer it will take you. Some charger who says they charge ultra fast is because they don't go into the CV mode.
@@julienc.4916
I agree with u sir, what u have explained is absolutely correct but there is a slight change. That
lithium ion or polymer battery never be charged to 100% bcz of voltage stress problem so, it's advisable to charge below 100%.
can u please send me any link related to CV mode
@@raviteja-bn2eg
It is a bit more complex than that. In fact to say a battery is 100% charged is a convention based on a protocol of charge and discharge given by the battery manufacturer and for which he guarantee a certain capacity. This protocol is a CC/CV with a charging stage and a discharging stage. Typical example of a protocol used to define capacity based on the IEC 61960 standard:
For the charging stage:
- Charge at 0.2C for the CC stage,
- Transfer to CV mode once 4.2V reached, and stop the charge once you reach current defined by a fraction of C, or stop after a defined period of time, typically 1 hour.
For the discharge stage, this one is used to calculate your capacity:
- 0.2C discharge current,
- End of discharge at 3V.
Capacity is simply given by the expression:
C (mAh) = discharge time (hours) x discharge current (mA)
You can find these information by reading the IEC 61960 standard.
When i say it is a convention, a battery manufacturer can decide to use its own CC/CV protocol, which can be more favorable to battery life, but will gove less capacity (you can't have all). It is better for example to define your CV charging stage at 4.1V instead of 4.2V for Li ion battery, as it will give less stress and give you higher cycle. But as i said, you'll have a bit less capacity.
hi sir,
i want to know when we charge battery in CV mode the current gets decreases slowly. but my question is that how they set the stop current for charging. is there any standard aboyt this
Dear Harshal Sable there is no general rule on that question. It depends. Some manufacturer will tell you 0.03 C, some 0.1 C. The smaller you set, a little bigger capacity you will get but not so much. And it will take you also more and more time as you tend to 0 C (until infinity in theory). Regarding existing standard, please refer to the IEC 61960. If my memory is good, they don't give a end of charge rule based on a value of the current in CV mode, but on a time basis. They say that your charge is finished one hour after you entered into the CV mode. It is up to you, but that may be a good start that you use this rule.
do u english
Too difficult for a layman to understand.