Calculating the State of Charge of a Lithium Ion Battery System using a Battery Management System
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- เผยแพร่เมื่อ 15 มิ.ย. 2024
- The State of Charge (SOC) is like the fuel gauge in your car, telling you how much energy is left in your battery system. Calculating the State of Charge in a lithium-ion battery system requires an understanding of how the battery pack capacity and energy change. This understanding is critical before diving deeper into Coulomb counting.
Topics Covered
State of Charge
State of Charge (Capacity) (SOCcapacity or SOCc)
State of Charge (Energy) (SOCenergy or SOCe)
Fuel Gauge
Coulomb Counting
Depth of Discharge
Open Cell Voltage Lookup
The state of charge is defined as the capacity remaining divided by the total capacity of the battery pack. We look at an example of how the state of charge is calculated. Using a discharge curve, he explains that this curve is not linear. Given this, the true state of charge is often different from the energy remaining. Looking at State of Charge (capacity) and the State of Charge (energy) we can understand the differences between these values and how to calculate the most relevant information.
Coulomb counting is discussed next. Coulomb counting integrates amp hours and time to calculate the capacity removed from the pack. This provides a basis for SOC. The current sensor has drift and measurement error, so it is also important to have an open cell voltage lookup.
Learn more at staflsystems.com. - วิทยาศาสตร์และเทคโนโลยี
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Excellent explanation ! Glad I found your you. Will continue listening to all your videos prior to asking a question. Thanks !!
Thank you for your videos. So simply explained. Your videos helped me to prepare for my interviews.
GREAT ONE!!!! The calculas everyone needs!
Excellent job. Clearly explained . Very eloquent !!!
Very informative video. Thank you for this. I just bought a 100Ah lithium battery and this explanation helps in understanding the app's SOC metric.
Clear and concise. Thanks for sharing!
Wonderfully done. Explained in very simple manner. So I guess one needs the charts for a battery pack to implement the socc soce and dod.
Thanks for the introduction. I really learn something.
Thanks for the explanation. You save my life
Thanks a lot, good explanation, keep going.
Very good explanation. Thank you!
Brilliant presentation!
Thank you very much for such a great video!
These videos are brilliant, Mr. Stafl, thank you, very easy to follow along. One gets into the noble field of lithium battery technology for environmental concerns, tries to brain-up on lithium battery characteristics and electrical fundamentals, and invariably gets stuck between principles and real-world application. Me for example. A coulomb meter out of the box needs initial settings ...specific to that battery config that it's monitoring... like capacity, full voltage "empty" voltage, and drift. A lithium battery pack's stated Ah may be, say, 40Ah, but is it the kind of parameter that ought to be tested for? And if it's "72v," obviously the range is going to be a few volts above (for full) and a bit above. (for depleted) But these are rules-of-thumb, and sort of nebulous to the amateur. To get specifics, should I test the voltage a.) immediately after charging, or after a day or two, and b.) idle or under load? In the interests of mitigating range anxiety, I'd like to make sure my settings are as specific/accurate as possible. You've got several videos. Is there one that may address these real-world scenarios best? Thank you.
Nice explanation!
Thank you very much very informative.
Very nice explanation!!
Great presentation! I knew there were nonlinearities in monitoring SOC and wondered how they did that. So now I know.
Your explanation beats what my professor has covered.
In you example 50% SOCe corresponds to 58% SOCc, doesn't it?...I think you mixed it up as you plotted over Ah discharged and not over SOCc initially.
Great presentation
Hi Stafl...A very good explanation
great information provided thanks
Very clear and brilliant presentation. Thanks a lot!
Informative video of what i exactly didnt understand about how you know what nn% charged means of a battery. I would ve appreciated if you defined the first SOC you wrote right away as SOC_c and in two different graphs you once mention Ah-discharged and DOD. Could have made them the same aswell.
Very good explaination
Excellent presentation bro
Thank you. You are awesome.
Very helpful .
Could you please explain calculation about charge or discharge Ah required for individual module depends upon min and maximum of cell voltage
Love the video.
Well presented
I’m impressed 👏🏼
Very nice Information sir 👍
Excellent video! Very helpful. One question, so does the BMS use voltage to determine the starting point for monitoring SOCe?
I would really like to see a LiFePO4 BMS among your product offerings .
Thank you 💐
Thank you!
OK, excellent information. Do you have a SoC code using C++?
I enjoyed the video.
I want to learn more about BMS. Is there any institution or certification you can recommend?
Yes, you bloody legend
At the 5:00 min. point, doesn't that point actually represent a greater than 50% SOCcapacity or is that 42% capacity used at that point? I think I understand. It seems that the 42% is more Depth of Discharge????
You are correct. The 42% figure should be Depth of Discharge (DOD) or 58% SOC. This is an error on our part.
@@staflsystems i was wondering the same. Thanks for the clarification
Good larning sir
Excellent info. My question may seem elementary but I understand quite a bit of what was discussed from my EE background. That said, I find one thing confusing. Is SOC and DOD the same with two 100ah lifepo4’s in parallel as one 100AH standalone lifepo4? I realize that I am getting 200AH with the parallel config and only 100AH with the standalone battery. With 2 in parallel, I would think that it should take twice as long to reach the 50% SOC level with the parallel config than in the single battery config, of course assuming the same load on both configs.
Hi Rich - thank you for your question. SOC and DOD are expressed in percentages, so they would be normalized to the size of the pack itself. For example, if you've discharged 25% capacity from a fully charged state, the SOC would be 75% and DOD would be 25%, regardless of if it is a 100Ah or 200 Ah pack. So if you have a constant load of say 25A, it would take you 1 hour to get to 75% SOC with a 100 Ah pack and 2 hours to get to 75% SOC on a 200 Ah pack.
" In general"..should be the name of this little video...
Hi! I have a small clarification.
It was said that energy distribution is imbalanced. We know that energy is Voltage times Ah discharged. Even though the voltage is high in the first part the X axis is at a low value. Will it not be compensated?
Thanks in advance for correcting me and clarifying it to me :)
The x-axis is the Ah discharged from the beginning of discharge not the instantaneous Ah
Hello, what is the internal resistance of the 4S lipo battery or what is it? I have a 5200mah 50C battery and the internal resistors are showing 7 ohms.
Do you think these values are normal?
I couldn't find the Video about Calculating SoC for various things like SoC for Energy etc .
Thanks for the clarity and simplicity
Mr. Stafl.. great videos
Can you pl make more videos
If we have a function approximation for voltage / SOCc curve, it would be easier to normalize SOCe from voltage than a lookup table. I would like to model that. Wonder if there would be use to that.
modeling a Voltage/SOC and measuring SOC based on voltage curve could be easier, but don't forget to consider the voltage drops on the battery itself due to internal resistance and the variation in voltage when charging.
at 6:45, how can I calculate that area. can you please help me in this ?. I have a device from that, I have a graph of Amps and voltage over the time and now I want to calculate total wh. how can I do this ?
Спасибо бро!
very nice tutorial sir, in my set up sir im using 2 pcs 24v 100ah lifepo4 batt. in parallel connection. my question is why is it that in my volt meter, display of my scc and in my inverter was 100% and when i scroll down in my scc srne 60a mppt the soc was 54% what is the defirence betwen them? thank you sir i hope i'ved got an answer sir. thank
Awesome explanation! However, I just want to make sure if I get it right:
1. DoD can be calculated through current measurement and time graph.?
2. The battery capacity is calculated by comparing its measured voltage to its Voltage-DoD graph?
The capacity is measured by coulomb counting. Capacity equal to integration of current by time.
from current and time get SOC, from SOC get DOD
If the battery is design only to take 80 mWh but test result it can be overcharged up to 90 mWh is that a normal Reading? thanks you.
Isn't no load voltage for a given charge level is a function of temperature of the battery?
So please was the right voltage to charge a 11.1v System
Quite so Mr. Stafl
Great
Interesting
My solar station software show SOC 3% and gradually increase but the voltage is above 12 so than why 3, or 5 or 7. It’s mean battery is too low . I am using Phoenix 230amp flooded
Fortunately to see your popular science video, we made a battery monitor KG140F, which can check the remaining capacity and current voltage of the battery, and can export the discharge curve, I think you should be able to use it, we want to send Give you a test.
Does 0% start from 2.5/3 voltage in phones batteries...?
WATT-HOUR is the real term that define remaining range/energy. Capacity is voltage dependent and each Ah at the end of charge worth less than the first Ah. So the REAL SOC is Watt-hour defined and not Capacity (Ah)
Is it possible Calculate Cell Or Battery Pack Capacity if Amp's don't Known?
PlZ Ans Me
Yes, but complicated.
if the battery is connected to load , How we gonna measure open circuit voltage in practical application ??
you cant , you will need to use some other estimation methods
My hypothesis would be that when the car is off or sleeping that that measurement is done. That's why when you park your car with 33% that when you get back in it might be 35%. Or 30%. It's possible it is more dynamic than that. It may do an instantaneous measurement during load reduction and calculate the delta from that.
But Amp.hours is a measure of energy. You mean the peak power available, potential to do work goes down over time because the voltage drops? I am confused.
@Nick Keller Yes, amps x volts = watts. The same 100 watt light bulb will draw more amps as the sos drops.
what is TCU error,While charging EV?
So what voltage corresponds to 50% SOC? That seems like a very critical piece of information that you didn't provide because, if you are trying to estimate either the mAh or total energy remaining, the simplest thing is to measure the voltage and use that as a proxy. I watched this video hoping to learn these voltages, but was disappointed when you didn't provide them. And yes, I do realize that Coulomb Counting is the more accurate method, but that doesn't help you if you simply "come upon" a loose 18650 and want to know how much capacity it currently might offer.
It would be better to define SOC(energy) as "SOE" or "State of Energy" and leave SOC for the lowly job of coulomb counting.
How do you the remained capacity"70ah"?
For example, you have a battery with 100Ah capacity. And you discharge the battery with 30A for one hour, there will be 70Ah capacity left in the battery.
@@yangjingxi179 thank you
Vak man!
"Remaing"
I got thrown off at the first 30 seconds no one got the misspelled word?
You look like PM.Justin Trudummy , or are you brothers??
From a professional video editor, there should never be any kind of music during any explanation videos ever
I totally dislike your BMS system because it can handle the ODD number of 12 cells, are you aware that most of the batteries in storage applicatins are 16 cells LiFePo4 ?
Then the total cost of just the BMS is way overpriced at 700+280+280=1260$ with the last monitor only half populated. Totaly ou of the residential storage market!
Not impressed
I think this presenter is mostly presenting his own confusion, there's no actual distinction between capacity and energy.
That's only true if internal resistance and voltage discharge curves are non existent.
Capacity is charge (Amp hours) and Energy is Joules (Watt hours), so the voltage profile is important.
Simplistic, theoretical nonsense, not corresponding to the reality of any particular LiFePo4. Have you ever bench tested dozens of batteries? Not one of them ever follows the maths or the graphs. New vs old; quality internal chemistry vs recycled lithium; hourly/daily/seasonal temperature variations; balance between cells; number of cycles; all conspire to make the only real SOC a specific measure of currents in and out from a daily top balanced cell reference point compared to the maximum actual battery SOH (State of Health). I have never, within real life situations, found a SOC figure to be any better than about +/- 8%.
The only true SOC is