BU-402: What Is C-rate?

Charge and discharge rates of a battery are governed by C-rates. The capacity of a battery is commonly rated at 1C, meaning that a fully charged battery rated at 1Ah should provide 1A for one hour. The same battery discharging at 0.5C should provide 500mA for two hours, and at 2C it delivers 2A for 30 minutes. Losses at fast discharges reduce the discharge time and these losses also affect charge times.

A C-rate of 1C is also known as a one-hour discharge; 0.5C or C/2 is a two-hour discharge and 0.2C or C/5 is a 5-hour discharge. Some high-performance batteries can be charged and discharged above 1C with moderate stress. Table 1 illustrates typical times at various C-rates.

C-rateTime
5C12 min
2C30 min
1C1h
0.5C or C/22h
0.2C or C/55h
0.1C or C/1010h
0.05C or C/2020h
Table 1: C-rate and service times when charging and discharging batteries of 1Ah (1,000mAh)

The battery capacity, or the amount of energy a battery can hold, can be measured with a battery analyzer. (See BU-909: Battery Test Equipment) The analyzer discharges the battery at a calibrated current while measuring the time until the end-of-discharge voltage is reached. For lead acid, the end-of-discharge is typically 1.75V/cell, for NiCd/NiMH 1.0V/cell and for Li-ion 3.0V/cell. If a 1Ah battery provides 1A for one hour, an analyzer displaying the results in percentage of the nominal rating will show 100 percent. If the discharge lasts 30 minutes before reaching the end-of-discharge cut-off voltage, then the battery has a capacity of 50 percent. A new battery is sometimes overrated and can produce more than 100 percent capacity; others are underrated and never reach 100 percent, even after priming.

When discharging a battery with a battery analyzer capable of applying different C rates, a higher C rate will produce a lower capacity reading and vice versa. By discharging the 1Ah battery at the faster 2C-rate, or 2A, the battery should ideally deliver the full capacity in 30 minutes. The sum should be the same since the identical amount of energy is dispensed over a shorter time. In reality, internal losses turn some of the energy into heat and lower the resulting capacity to about 95 percent or less. Discharging the same battery at 0.5C, or 500mA over 2 hours, will likely increase the capacity to above 100 percent.

To obtain a reasonably good capacity reading, manufacturers commonly rate alkaline and lead acid batteries at a very low 0.05C, or a 20-hour discharge. Even at this slow discharge rate, lead acid seldom attains a 100 percent capacity as the batteries are overrated. Manufacturers provide capacity offsets to adjust for the discrepancies if discharged at a higher C rate than specified. (See also BU-503: How to Calculate Battery Runtime) Figure 2 illustrates the discharge times of a lead acid battery at various loads expressed in C-rate.

Typical discharge curves of lead acid as a function of C-rate
Figure 2: Typical discharge curves of lead acid as a function of C-rate

Smaller batteries are rated at a 1C discharge rate. Due to sluggish behavior, lead acid is rated at 0.2C (5h) and 0.05C (20h).

While lead- and nickel-based batteries can be discharged at a high rate, the protection circuit prevents the Li-ion Energy Cell from discharging above 1C. The Power Cell with nickel, manganese and/or phosphate active material can tolerate discharge rates of up to 10C and the current threshold is set higher accordingly.

Last Updated: 25-Oct-2021
Batteries In A Portable World
Batteries In A Portable World

The material on Battery University is based on the indispensable new 4th edition of "Batteries in a Portable World - A Handbook on Rechargeable Batteries for Non-Engineers" which is available for order through Amazon.com.

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조영창

300F Capacitor에 25V를 축전하여 부하에 공급할때 부하에서 받을수 있는 Wattage는 얼마가 됩니까?
수초동안 축전하여 수초동안 사용하는 경우입니다.
Up/down Inverter로 축전시의 전류/전압의 제어가 들어가고 방전시도 Up/down Inverter로 부하에 필요한 전류/전압으로 변환하여 인가시키려하는데, 300F Capacitor에 어느정도의 에너지를 넣고 사용할수있는지 의문입니다

Sharil

Hi...I have a question

I need a 450A current for 10 second. Does a 100Ah battery with 1C rating will do

Ravy1981

Can you use .5C as a 1C Battery if you double the quantity, and vice versa can you use a 1 C battery as .5C battery ?

R.Kesavanarayanan

What is the charging units and discharging units of 2v 1000ah battery per hour what is the calculation.
can one battery give's the discharge units is more then charging units?

R.Kesavanarayanan

What is the charging units and discharging units of 2v 1000ah battery per hour what is the calculation.
can one battery give's the discharge units is more then charging units?

R.Kesavanarayanan

What is the charging units and discharging units of 2v 1000ah battery per hour what is the calculation.
can one battery give's the discharge units is more then charging units?

Karl

I have a lithium phosphate 170ah battery in my campervan that has a lesser rating of 1C. However if i max out my 2000w inverter, its pulling energy from the battery equivalent to nearly a 1c 170amps. Will this damage my battery or is it a case of under rating the battery or just that its new?. The manufacturers of the inverter don't recommend my battery pack with this inverter. Both products are made by renogy. Will i damage the battery if i draw more energy than the C rating??

Mark Sullivan

The energy capacity of any battery is a function of discharge rate. Fundamentally, this is true because there is no such thing as zero internal resistance. It's not that somehow there is less stored energy at higher current more of the available energy gets converted to heat and is there for not available as electrical power at the terminals. Even within lithium cells there are so called power cells that are optimized for high discharge rates and energy cells that are optimized for larger capacity but of necessity at lower rates.

Frank McGraw

why is energy capacity of a lead acid battery a function of discharge rate and for a LiFeSo4 battery it is not?

Dradriga Patrick

Thank very much for this great site.
I have been searching for this rich information until i was referred by a friend here.

The link for the analyzer test equipment shows it is empty.
Any help on how it looks like and to use it so that i an use it to study my batteries please?

Thank you.

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On August 21, 2019, Sam wrote:
We need to load a Li ion battery pack of max 25V and max 10A having 18650 Li ion battery cells by varying different C rates while continously observing SOC and SOH of the battery pack.Please suggest a Battery Analyser to serve our purpose. Also the price and specifications of it.Thanks in advance.
On August 14, 2019, SVRK Prabhakar wrote:
Hello all, I am just starting with an advanced multi-chemistry charger (Revolectrix Powerlab 6 T) that allows programming specific charging/discharging parameters. I have been struggling to get reliable charging/discharging parameters on the web world with everyone claiming different charge rates, termination voltages, max charging voltage, min charging voltage etc. Can somebody please provide me with the following values for various types of battery chemistries (Pb, NiMh, Li-Ion, LiPo etc)? That would be a great help. Cell voltage (Max and Min) Charge and discharge termination voltages* Charging rate, max (and min if applicable) either in C rate or in Amperes Storage charge termination voltage* *It would be great if these values can be provided for accurate charging, normal charging, fast charging, discharging, storage charging, etc. per cell (given LiPo comes in packs of cells) I would be grateful if these values can be provided for the following chemistries/types: NiMh, NiCd, LiPo, Li-Ion, Pb Acid Thank you so much in advance for your kind help in this matter. Regards Prabhakar
On July 20, 2019, Yash Raj wrote:
The real capacity of the battery changes with discharge rate. Right? So how is capacity of battery related to discharge rate?
On July 6, 2019, Laurence Darby wrote:
My understanding is C means "batteries per hour", and it's completely independant of the capacity. Example: discharge at 2C. Replace C with "batteries per hour", so that's 2 "batteries per hour", or 1 battery in 30 min. See? Another example: Charge a battery at 0.5C = 0.5 batteries per hour, or 2 hours for complete charge. C rate doesn't tell you what the current flow in amps is, because that depends on the mAh rating, which is different for all batteries, that's why I hate C rates!
On October 1, 2018, royce wrote:
Thanks for the info. Question: What is the difference in capacity between— 1. SLA 12v 5ah battery, and 2. Li-po 5v 16.75ah battery On the surface, it looks as though the Li-po has more capacity (60 vs 83.5). But the SLA is 2-3 times heavier than the li-po. is it just a difference in newer technology? Price difference? (lipo is 2-3 times more expensive than SLA) What am i missing?
On May 19, 2018, Tamadite wrote:
How should I interpret "0.2C5mA" in the following context? ============ Capacity : Nominal 650mAh Recommended Charging Conditions:0.2C5mA charge termination control parameters taper current 0.01C5mA at 8.4V ============ The "0.2C5" format is what puzzles me.
On February 28, 2018, Hadi rizvi wrote:
thanks for information about C Rate.
On February 28, 2018, Sandip Ghosh wrote:
Generally solar applications, we use C10 rated lead acid batteries. This batteries are discharged upto 80%. Whereas in normal inverter duty lead acid batteries used for emergency back up uses c20 rated batteries and they are discharged upto 65%. If we compare the back up of 120Ah, 12 V c10 solar battery and 150 Ah , 12 V c20 inverter battery the backup time for both the batteries are practically equal if same load is applied. I need your input on can we conclude that back-up off C10 rated 120Ah solar battery is equivalent to C20 rated 150Ah inverter battery.
On February 25, 2018, Meaco wrote:
I'm from pa I would like help helping my fellow Pennsylvanians and west Virginians with some cleaner generators for Cole mines anyone want to help
On February 25, 2018, Michael lynch wrote:
I would like to help Cole miners so I need to know everything thing I can so I can make at least hybrid generators
On February 10, 2018, Pharouq wrote:
pls can somebody enlighten me about the methods of charging a battery specifically, (lead-acid battery).?
On January 31, 2018, boopathi wrote:
i am designing a electric tricycle.my motor's load is 20A,1000W .my battery discharging rate is 0.2C .,its capacity is 42amphr. can i use this battery??? OR Do i need to change the battery???
On December 25, 2017, Xenofon wrote:
Lithioum Batteries with lower C rate has better life time than batteries have higher C rate? for example 1 LiPo RC battery Have 10C discharge rate 1C charge and it is 3S 5AH and the other it is 3S 5AH 25C discharge and 1C charge .Both of them charge 0.5C and discharge 3C which of the two will have a longer life?and why? I looked at your site but I did not find an article on this subject .Τhank you very much i am from Greece.
On October 15, 2017, Ligin Hananiah wrote:
I need a battery for 48V 1500W hub motor. I need to use it atleast 3hrs continously which battery capacity and C rate can I choose?
On August 10, 2017, Sung Ji Cho wrote:
I feel like C rate is better described as Amp / hour. For example, a battery with 1 Ah capacity provides 1 Amp per hour for 1 hour at 1C, and the same battery rated at 2C provides 2 Amp per hour for 30 minutes.
On June 29, 2017, Dolf van der Heide wrote:
Is there a unit associated with C-rate or is it dimensionless ? Does the word rate mean per time unit?
On March 29, 2017, Occam wrote:
Can anybody explain why does voltage decrease when C-rate increases?
On December 24, 2016, robert wrote:
Hi guys. Is C-Rating Abbreviation fo Charging-Rate? thanks for your answers
On November 23, 2016, Mike Chapman wrote:
I have a need to charge 12 or more AA NiH batteries in series to make a battery pack to simplify the charging process. What are the issues including the charging rate and duration. Are there any safety issues?
On August 15, 2016, Sakir Husain wrote:
Please said me, when i will battery HRD TEST, IF 180AH Battery Capacity , how can i selecte A3 c Ahmpere, 180*3=540 its ok, and cut of voltage 7.5 is proper Setting for HRD Result
On August 8, 2016, pooja wrote:
If i have a model which allows 10C charge/discharge rate, and i require only 3C, So can i do the sizing with respect to 10C i mean to reduce number of batteries. Please explain
On July 22, 2016, Lucho wrote:
How can man calculate the maximum current in a battery working till DoD = 50%? 12 V 200 Ah with DoD = 50% C-rate = 5: In 5 hours I get E = 2400 Wh with I_max = 40 A or E = 1200 Wh with I_max = 20A?
On June 14, 2016, Evan Kurtz wrote:
Not a battery person...looking a some spec sheet I see charging rate but C ratign talk about discharge rates...Can one assume there are the same? My gut feel is no but it may depend on battery chemistry etc. Thanks
On June 10, 2016, Marko Stanojević wrote:
C100 is the regimen that charges/discharges a battery in 100 h. The rating you provided means that, when the said battery is charged/discharged at C100 rate, it will store/provide 240 kWh of energy. This is, of course, implying that during such discharge, the rated voltage will remain just that - (practically) the same. Since you did not provide data regarding the battery's rated voltage, I'll provide a calculation for a case of a 12 V battery. The common way for describing battery capacity is in Ah. 240 kWh is 240 kVAh, which, for a 12 V battery, gives the C100 capacity of 240/12=20 kAh, or 20,000 Ah. From this we derive that the battery's C100 rate is 200 A. In conclusion, the battery whose (incomplete) rating you provided would, if it were a 12 V battery, have a C100 capacity of 20 kAh and a C100 charge rate of 200 A. Hope this helps.
On June 6, 2016, Anja Rindstad wrote:
An AGM battery has a C100 capacity of 240 kWh. What does that mean?
On May 13, 2016, Marko Stanojević wrote:
I accidentally removed myself from the comments recipients list, as I had commented on this article previously and have been receiving notifications. I am still interested in the development of this article/discussion. This is only for re-enlisting purposes, as I haven't been able to find another way. Sorry for the inconvenience.
On May 13, 2016, Marko Stanojević wrote:
Accidentally removed myself from the comments recipients list, as I had commented on this article previously and have been receiving notifications. I am interested in the development of this article/discussion. This is only for re-enlisting purposes, as I haven't been able to find another way. Sorry for the inconvenience.
On May 12, 2016, Larry Becque wrote:
correction: 3. ..... 1C would be a charge of 1.9A.
On May 12, 2016, Larry Becque wrote:
@Danny Gonzalez The information you provided is very confused but I will try and provide answers. 1. C rate usually applies to the individual cells but can also apply to a pack made up of cells arranged in series and parallel. The difference is that if you are charging a pack with two sets of cells in parallel (doesn't matter how many are in series) you must apply twice the amperage to achieve the same C rate for charging. When the cells are arranged in series the charge current (amperage) remains the same but the voltage increases by a multiple of the number of cells. 2. Not sure why your battery is rated C5 for charging. LFP normally charge at 1C. Check with the manufacturer. Perhaps what they mean is that you have 5 sets of cells in parallel in the pack so need to apply 5 times the current you would apply to a single cell at the 1C rate. 3. 13.2V for the pack divided by 3.3V nominal Voltage for a LFP cell means that you must have your cells arranged in sets of 4 cells in series. Assuming from the above that you have 5 sets of cells in parallel this means you have a total of 20 cells. 38Ah divided by 20 cells equates to 1,900 mAh per cell which seems reasonable. So 1C would be a charge of 1.8A. 4. 20V sounds like way too much voltage to charge this pack. LFP cells normally charge to 3.65V per cell max. With 4 cells in series times 3.65V this means 14.6V would be the max voltage to apply to the pack. 5. Li batteries are charged at constant current then constant voltage with the current reducing. The mfg should give you both an amperage and voltage limit for charging the pack.
On May 6, 2016, Danny Gonzalez wrote:
Thanks for this site. I refer to it often. I'd like to be sure about charge voltages and I'm confused by the C rate designations. Is C rate defined by the specific mah capacity of each cell in a pack, or is it defined by the aH rating of the pack as a whole? I've just bought a 13.2v 38ah lithium phosphate battery and it appears to be charge rated at C5. It seems that it's made up of 26650 cells.The MFG spec states that 20v is the recommended charge rate and calls that C5. What is the acceptable charge range for it (Im expecting to end up with a disharge rate of around 14 hours in my application, should that matter)?
On January 23, 2016, Ren wrote:
A new battery is sometimes overrated and can produce more than 100 percent capacity; others are underrated and never reach 100 percent, even after priming. I thin you meant it other way around. If battery is overrated then in reality you would never achieved the mentioned charge/discharge. Like many of the chinese batteries. Some are rated at 5000mAh but achieve only 100mAh. These are overrated batteries.
On January 15, 2016, Roy Emmerich wrote:
Correction: "At 1C, a battery rated 1,000mAh charges at a current of 1,000mAh." should read: "At 1C, a battery rated 1,000mAh charges at a current of 1,000mA."
On January 14, 2016, lal bahadur singh wrote:
can you explain in depth, how to test a new cell in lab. to understand it's anode'/ cathode capacity, after fabrication of cell with graphite powder and liCOo2 cathode, thru battey analyser.THEMETHODOLOGYAND SETTINGS OF VOLTS AND CURRENT VIS A VIS ELECTRODE SAMPLE WEIGHT.
On November 26, 2015, anaz wrote:
in c10 ratting how much oncharing volt is disconet?/
On October 23, 2015, Robert Dubé wrote:
@Hardware Freak Simple arithmetic will give you the answer; 1 / 0.8 * 0.9 = 1.125h in decimal time which is 1h 7m 30s (0.125 * 60 / 100) But that is all very theorical; is the battery really charge to full capacity (is your charger calibrate?), C is from what is written on battery or measured? If written on battery, what are spec from manufacturer to calculated Ah (charged to 4.4v and discharged to 2.6v or 4.2v to 3.0v? and at which rate is it discharged?) and so on...
On October 7, 2015, Hardware Freak wrote:
If I Discharge a Li-ion Battery at 0.8C, what will be the time taken to disharge 90% of the Battery capacity
On September 30, 2015, Larry Becque wrote:
I agree with Marko, the first three paragraphs need to go or be rewritten as follows: In the late 1700s, Charles-Augustin de Coulomb ruled that a battery receiving a charge current of one ampere (1A) passes one coulomb (1C) of charge per second. On discharge, the process reverses. Often in engineering terms, the letter C is used as a symbol for one Coulomb of charge but this should not be confused with the C-rate which is different. C-rate is defined as the charge / discharge current divided by the nominally rated battery capacity. For example, a 5,000 mA charge on a 2,500 mAh rated battery would be a 2C rate. A 2,500 mA charge on the same battery would be a 1C rate and would theoretically fully charge the battery in 1 hour (assuming 100% charge efficiency). The capacity of rechargeable batteries is commonly measured in Amp hours at a 1C rate particularly for Li-ion chemistries. However, in some cases capacity is measured at a much lower C-rate typical of their intended use as in the case of small alkaline consumer batteries and sluggish lead acid batteries.
On September 30, 2015, Marko Stanojevic wrote:
I suggest that this article is edited as to drop the first three paragraphs, as C-rate does not have direct connection with the unit of electric charge, Coulomb, that also bears the same designation, C, as they do not add to understanding of C rate. On the contrary, they only add to possible confusion, as is reflected in some comments. The primary reason for the introduction of the C-rate is the need to address the current with which a battery is being charged (or discharged) in terms that bear more relevance to that particular battery than just stating the absolute current value. Since the load (I will use this term for both cases of battery being either charged or discharged as in both cases higher currents present similar challenges) is relative to the capacity of a battery, the C-rate is used to describe the discharge or charge current in terms relative to it's capacity, that is, to the current that would, under ideal conditions, discharge a fully charged (or completely charge a fully discharged) battery in one hour. Therefore C-rate is a good way to really get a grasp on the load placed upon a battery, regardless of whether it is during the charging or discharging process. C therefore, in this context, represents a way to describe current, not capacity of a battery, although it is particularly related to its capacity. It is useful to describe a regimen in which the battery is being used regardless of its capacity, so two batteries of different capacities but of the same type can be, current wise, described in mutually comparable terms. Of course, different types of battery chemistry have different requirements, or rather interpretations. of what actual load in fact represent a current of the same C rating. Therefore, you will only need to know a universal, C-rate based characteristics of a given battery type (chemistry) and will be able to convert this to actual current values depending on the battery's capacity.
On September 29, 2015, Bibek wrote:
I really like this website. Thank you for sharing . However i was wondering how depending upon the C-rate the capacity of a battery changes? Like with higher C-rate capacity will decrease and lower C-rate capacity will increase? I read that resistance increases with higher C-rate but can i have detail explanation on the chemistry part and in electrical part too? Thank you in advance
On June 19, 2015, Larry Becque wrote:
This article needs some rewriting as it is confusing and never really answers the question in the title: what is the C-rate. After introducing the Coulomb and correctly defining it as 1 amp / second = 1C (Coulomb) the article wanders in other directions leaving the reader with the wrong impression that the Coulomb and C-rate are the same. They are not. Wikipedia defines the C-rate much more directly and clearly as: https://en.wikipedia.org/wiki/Battery_(electricity)#C_rate The C-rate is a measure of the rate at which a battery is being discharged. It is defined as the discharge current divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour.[29] A 1C discharge rate would deliver the battery's rated capacity in 1 hour. A 2C discharge rate means it will discharge twice as fast (30 minutes). A 1C discharge rate on a 1.6 Ah battery means a discharge current of 1.6 A. A 2C rate would mean a discharge current of 3.2 A.
On February 9, 2015, Marko Stanojević wrote:
The first paragraph of this article contains the reference to the unit of charge - Coulomb (C) which, in addition to not having any strict relevance for what follows, only creates a possibility for confusion with the charge-rate designation bearing the same symbol. Since the conventional way of describing the battery capacity is in terms of (MetricPrefix)AmpereHours, the logical and intuitive way of describing the charge-rate is the introduction of C, the current which ideally fully charges a completely discharged battery in one hour, and expressing the charge-rate in relation to this quantity.
On September 20, 2014, RK PILLAI wrote:
What is the rate of charging current for lead acid batteries of different capacities? Is there any universal charging rate? If the manufacturer has not mentioned any rate of charging, how can I fix the rate? kindly give me a reply.
On September 1, 2014, subbareddy wrote:
dear boss ihave one doubt is how can i calculate the charging current ampere and discharge current ampere iwill give the one ex:225ah,1.2v/cell how much the current ampere
On July 29, 2014, Yogesh Yadav wrote:
Dear All we have battery charger of 270 V, 10 Amp, i want to know that what no of batteries i can charge on this of 12V 7.5 AH.
On April 17, 2014, Steve wrote:
@Anne I have sent an email to that address, let me know through that address if you have received it :D I can answer your questions from this forum through that address if it works!
On April 17, 2014, Anne wrote:
@Steve (Ignore the mistakes, I wrote too fast...) When you send me a mail I will reply with some images, this makes discussion easier (and I can not add pictures here, so mail is the best).
On April 17, 2014, Anne wrote:
@Steve Hi, I also was (better said am) busy, but I want to still write here. First of all: what device do you use (can you give me a name or so)? As I wrote we have two different ones, so it depends a bit if its more of a battery cycler or a potentiostat (at least in this way we name or two ones). ... It would be best if we could write mails, please write me on this adress (just a note is enough, that I have your address): vi-friends.v.af(at)web.de Since is address I normally don't use, its just for such cases (I will write you back from another, so don't wonder; I do not want to write my real one here, because I already get enough spam mail ; )
On April 16, 2014, Steve wrote:
@anne: In follow up I have some questions about the voltammetry; I plan on using the technique myself XD but in my initial learning I didnt see how it could be applied to a theoretical capacity. Wont the measurement only tell you the potentials at which reactions inside the cell are occurring? i.e. lithium insertion/removal? I think that you would need some sort of time scale to know the amount of charge you are putting into the batter? Or perhaps you are cycling until you no longer see a reaction taking place?
On April 16, 2014, Steve wrote:
@Anne: I have been busy working over the past few months, if you still check this site i would be happy to try and get a discussion going on. I am somewhat hesitant to put my skype name or email up on a permanent online post, but I think there could be a way to get in contact at least through an email. Let me know if you are still using this with a post! I plan on checking this page for a week or two.
On April 15, 2014, Jagat Modi wrote:
Can any body share the probability of lead acid automotive battery being exploded durting cracking of an engine ? And also the same battery being used for DG starting with permanent float cum boost charger connected ? And what are the SOP for lead acid batteries used for such applications ?
On April 15, 2014, Jagat Modi wrote:
Can any body share the the probability of lead acid automotive battery being exploded dusting cracking of an engine ? And also the same battery being used for DG starting with permanent float cum boost charger connected ? And what are the SOP for lead acid batteries used for such applications ?
On February 27, 2014, harry potter wrote:
do you use skype? If yes we can also discuss there. - It would be awsome if a discussion of e.g. batteries could be done between different scientist via skype or something else, so that everyone get soon help… i just want to ask something about that battery and explain me how to make it in russia\\ benelmokadem <a href="">harry potter movies in order</a>
On January 30, 2014, Anne wrote:
(Do you use skype? If yes we can also discuss there. - It would be awsome if a discussion of e.g. batteries could be done between different scientist via skype or something else, so that everyone get soon help...) Hm, I just tell about our devices, maybe this helps you. If we run cyclic voltammetry in our old device we just have to add the parameters voltage range, scan number, Esteps and scanrate. Than you get a diagramm in which the voltage is the x-axis and current is the y-axis. Than you just have to calculate the area under the redox-peaks and with this (and the active mass) calculate the specific capacity. If we use our new device we get a diagram in which the time is the x-axis, one y-axis is capacity and the other one is the voltage. Before the measurement here you have to add a c-rate. I guess it is like this: If you take the theoretical capacity of your system &#40;Ah/g&#41;, transform this to your actual active mass you get the number you need for e.g. 0,1C. Right now I can not tell you more, I do not really know what this fig.1 in the link is (but I work not Li-ion batteries). Does this help somehow?
On January 29, 2014, Steve wrote:
@Anne: Thanks for the response! I am at the same place you are then :) When you run cyclically (potentiostat), I assume you then get the capacity related to the current over time? Do you know how this compares to a "typical" charging profile where you hold the current (then the voltage) constant? http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries Bump for the question on a method to calculate the theoretical capacity!
On January 28, 2014, Anne wrote:
@Steve: If you just run cyclic voltammetry (potentiostat) you do not need any capacity value, you get it from this experiment. If you use a battery cycler you need a C-rate (so: yes, using different C values is possible, most people does). If you need the theoretical capacity of your system &#40;e.g. for Li-S, in the literature&#41; or the capacity for your exact testcell I don't know (that's one of my questions).
On January 28, 2014, Steve wrote:
It sounds like to me you need to know the theoretical capacity of your battery before charging/discharging to apply this system? Is it possible to test your battery's capacity using different C values if you are testing new anode/cathode technologies?
On January 20, 2014, Jaan wrote:
The C-rating has nothing to do with the physical unit "coulomb", so the first sentence of the article is misleading. 1 C is indeed the standard abbreviation for the SI unit 1 coulomb, but in this article, the notation 1C is used to mean a totally different thing! "Coulomb" is a unit of charge; it is just another word for ampere-second and could be used for measung battery capacity instead of milliampere-hours: 1 coulomb = 1 A * 1 s = 1 A * 1/3600 h = 1/3600 Ah = 0.278 mAh. What is denoted by 1C in this article, has actually the units of frequency, i. e. 1C (in this article) = 1/(1 h) = 1/3600 Hz = 0.278 mHz (millihertz).
On January 17, 2014, Anne wrote:
I am also new on developing new batteries and have a similar question. We have two devices: the old we used for CV and impedance and with the new (better) one we can also measure e.g. constant current measurement. So when we want to start a test with the new device we have to add a c-rate. Since we do not know the capacity of the test cell, do we first have to measure CV on our old device to know the highest achievable capacity, so that we can calculate e.g. 0,1C? And: On our old device every cycle of one test cell needed the same time. In the first tests with the new one we noticed that the time for one cycle depends on the capacity of the cell (so a short cycle shows less capacity in the capacity-cycle-diagram). Does this mean that the new device notices when all active material has reacted and automatically starts the charging process, or what else can be the reason?
On November 20, 2013, Olddawg wrote:
Oh so many more questions... What is the seperation? What is the solution involved? How is it being circulated? Area of plate (if plates are involved)? Quality of all? Many more could come.. Oh my! It's not just as simple as capacity of either.. or both combined.. If no one else here 'chimes in' and you wish to continue.. Please send me a personsal email. I will hook you up with some very good minds I work with! Let's see if this site can get you going first. If not, write me!
On November 20, 2013, naresh wrote:
Thank you, Actually I am new to this field. That is why I am getting these silly questions and I am learning slowly and after that only I will start making the battery. One last question is that while calculating the theoretical capacity of a new battery do we take only cathode capacity or only anode capacity or combined capacity.
On November 19, 2013, Olddawg wrote:
You're in new territory for me with a newly designed battery! You're thought of using the theoretic capacity is good for charging. I still would go lighter and time it. You may again find it will take 30hrs, yet better that going full and charging in 10hrs and slamming the battery with too much. To me (MHO), the real test of capacity is going to come with dis-charge. Without knowing what you truly have as a concept, and the possibilities being abundant, it's difficult to say "Do this"... Initial charge of something I just built, personally, I'd have a hard time going over 50% of what I believe it will do. Especially for the first run.. I've burned out too many good ideas (circuits) because I ms-judged the capability. I wish you great success in your endeavor! Please keep me posted as to your results.
On November 19, 2013, naresh wrote:
Thank you for your replay mr. Olddawg. You mean to say that we have to select the charging current such that it can full charge (100% capacity) the battery in 20 hr. Once we do this we will find out the full capacity of battery and according to this full capacity we have to select the C-rates. Initially I thought that we need to select the C-rates according to the theoretical capacity of anode and cathode (combined capacity) do we select C-rates according to theory?.
On November 18, 2013, Olddawg wrote:
You don't choose C-Rate. The response of dis-charge determines the C-Rate. Since you're developing a 'new' battery (of which I'd love to char further), I would start dis-charging small and work your way up. You only know what you anticipate from the battery. I used half that to draw and time it. You may find you are correct and it draws 30-40+hrs before done. Then you have a C30-C40 battery. Up the draw till you hit the 20hr time length. Now you have the draw matched to the battery. 'Done', becomes the next question.. I'll await..
On November 18, 2013, naresh wrote:
can any one explain, how do we choose the C rates, when we are developing the new battery. I Mean we do not know how much capacity it can store, in this case how we can choose the C rates.
On July 16, 2013, Jason wrote:
On March 15, 2012 at 10:32am gianni pup wrote: On Li-ion battery cell technical specification I found the following charateristic : Standard charge = ” Standard charge ” means charging the cell with charge current 1075 mA and costant voltage 4.2 V. at 25°C., 0.02 cutoff. Could someone explain me the meaning of cutoff ? Many thanks in advance ! =============================== In the case of your Lithium-ion charge, it interprets as the charger will begin from Constant Current(CC)mode, at the point when the voltage reaches 4.2V, the charger switches to CV(constant voltage) mode; the charge process won't end until the current drops to the threshold of 0.02(20mA)
On July 10, 2013, Olddawg wrote:
I came her to understand what a 1C is compared to a C1 rate. What I understand is that it's only an invert stat that means the same. A C20 battery, which I work with, is a battery rated at a 20 hour draw. Then could be stated as 20C A 1C battery is the Ah at 1 hour draw Then could be stated C1 It all comes down to the amount of time the battery can be drained. Drain your battery, time it. That's your real C rate of use. Want to improve the result because it's under-performing?? De-sulfate the battery.
On May 23, 2013, gunwoo wrote:
1C is a 1000mAh battery in one hour to supply 1000mA when you when 0.5C, 2C change when going to both the current time and why? When the total current 1000mA La 0.5C to 2C if ilttaen 2 hours 30 minutes 1000mA 1000mA supply is wondering whether or not haneunge?
On March 26, 2013, thinira wrote:
can anyone explane what is charge capacity, discharge capacity and coulombic efficiency?
On September 6, 2012, hifasath wrote:
sir ,, i had on no of 12v 150ah c20 & 2 nos of 80 ah which will make better performance
On May 28, 2012, MySchizoBuddy wrote:
What about min and maximum charging current for a particular battery capacity.
On May 16, 2012, Steve Spence wrote:
The term everyone seems to be dancing around is peukert. If you have a 100ah battery at the c20 rate, you can discharge at 5 amps, for 20 hours. If you pull faster, you'll have less capacity, if you pull slower, you'll have more. You can calculate this at http://green-trust.org/peukert/
On May 4, 2012, styvens wrote:
@ Jon your quick example is much more explanative than the whole paragraph who seems to circle around...
On April 15, 2012, gurivireddy wrote:
Hi, can some if explain me what happens to the C-rating if I connect two identical batteries in series, and in parallel. do they change or they remain same? thanks in advance
On March 15, 2012, gianni pup wrote:
On Li-ion battery cell technical specification I found the following charateristic : Standard charge = " Standard charge " means charging the cell with charge current 1075 mA and costant voltage 4.2 V. at 25°C., 0.02 cutoff. Could someone explain me the meaning of cutoff ? Many thanks in advance !
On March 8, 2012, Jon wrote:
Johny-- I believe that in your example you'd still have a 1C battery (pack). Assuming the following batteries: (4) 12V, 10AHr batteries (1C: thereby capable of delivering 10A over 1Hr) Hooking them up in parallel, you'd end up with a configuration that is: (1) 12V, 40AHr battery pack (1C: thereby capable of delivering 40A over 1Hr). Therefore, you'd still have 4x the current capability of a single battery (40A, instead of 10A), but it would not be possible to drain the pack in about 1/2 hour (as with a 2C battery), or about 15 minutes (as with a 4C).
On February 12, 2012, Johny wrote:
So, to achieve the desired C-rate, the batteries must be connected in parallel circuit... If I 've got 4 x 0.5C batteries with 12V, I can set a combination to 2C and 12V. Is it correct understanding?
On January 19, 2012, Howard Silverwater wrote:
With using a 38 Ah deep cycle lead acid battery and at discharge rate of 20 hours (ham radio 75% duty cycle; receive at 1.7A and transmit at 5.5A) with a solar panel supplying 0.8 A, why does a 12.25 V reading during transmit (5.5A) give a lower SoC (state of charge) than if I was NOT to consider the solar panel contribution and used HIGHER discharge rate (of ~14 hours)? According to typical lead acid graphs showing SoC vs. voltage while under discharge, a reading of the same 12.25 V shows a higher SoC for a faster discharge rate. I would expect an influx of 0.8 V from solar energy that contributes to slow down the discharge rate to show a higher SoC. What’s wrong with line of thought?
On November 22, 2011, Srdjan Dragojlovic wrote:
I have system with 110pcs of 450Ah/2V in serial connection. I have problem with battery system. How I can find problematic battery?
On October 21, 2011, Crazy Casta wrote:
Your graph is confusing. Shouldn't 1h=1C, 3h=0.333C and the 1C line be coincident to the 1h line?
On September 15, 2011, amutha wrote:
how much charging time is required for 1 day back up of the rechargeable battery?
On August 22, 2011, Matt wrote:
C-rates are the rate of discharge (or charge) as compared to the capacity of the battery. A 1C discharge will be the current that would seemingly go through the rated ampere-hours of the battery in an hour. A 2C rate is twice that current. A 0.5C rate is half that current. In the specific case of a 1 Ah battery given above, the numbers come out equivalent to amps, but in the general case, the C rate is different. For example, a 5 Ah battery would (by rating alone) have a 1C current of 5 amps. A 2C current would be 10 amps. The 0.5C current would be 2.5 amps. The real capacity of the battery changes with discharge rate though, so actual performance differes from the ideal capacity.
On April 29, 2011, Luca wrote:
So the C-rates are just another way to express a current? 1C=1A (Ampere), 0.5C=0.5A= 500mA, 2C=2A=2,000mA ?