Calculating the State of Health for a Lithium Ion Battery System

A battery's State of Health is critical to understanding how a battery degrades as it is charged and discharged over time. This degradation is caused by the increasing impedance of the cells. This video explains how this is calculated and some easier ways to understand how a Battery Management System monitors and reports this information.

Topics Covered
State of Health
Discharge Cycles
State of Health Capacity
State of Health Impedance
ESR
Estimated Range Remaining
Range Calculations
Battery Capacity Fade Effect

State of health, or SOH, is commonly defined as the total capacity of the battery pack today divided by the total beginning of life capacity, given in units of Amp Hours. We explain how this is calculated by the Battery Management System and why understanding state of health is important for a system. State of health explains the degradation of the battery over a number of discharge cycles.

We also look at State of Health impedance as well as the more common State of Health capacity. Over time, the ESR, or impedance, of the cell will grow. This increasing impedance decreases the state of health. A battery management system looks at both of these calculations to understand how a battery pack ages. This changes how the range of a battery pack is calculate for an electric vehicle.

[dhadumia]

Thank you for sharing such knowledge! And so crisp and clear explanation!

[hamidalsaid]

Phenomenal way of explanation!. Well done Erik

[lindsayshantharubia]

You are just awesome!!! The concepts are not just clear but the way you teach also intrigues me to learn more from you, !! <3 <3

[ketanpatel]

very well explained and informative.. thanks

[whoknowswhodoesnt]

This explanation is superb, thank you. And could you please elaborate on how one can measure the actual battery capacity, for example of an electric car?

[KPsCoaching-svpw]

Excellent.... Very informative video....

[ncm]

Very informative and easy to understand

[itstrysten]

I wish you would have mentioned the cause of wear. High current charging and discharging, over-charging, and thermal stress all contribute significantly to SoH dropoff

[vtorsi]

If the 70% SOC is measured in units of amp-hours then you would have LESS THAN 112 miles ( = 160 miles x 70% SOC ) remaining, due to the lower voltage and therefore lower energy. Whereas, SOC(energy) would be ~112 miles, until "empty" ...

[mouncefsenhaji]

You are the best ! thank you so much !
Any videos about the kalman filter ?

[sureshkumar-ccjq]

Great Work Sir, God bless for you time spending to explain the concept. Please apply Kalman filter and show the estimated range of drive.

[mikkaeldunlop]

Sir Erik, how did you derive the 160Miles from the current max range I am a little bit confused? Can you help?

[bharathsk]

Is it possible to measure the temperature of battery cell with the help of measured internal impedance of the battery? EIS method

[michaelgap]

In another video you go into details of SOC(capacity) and SOC(energy). Wouldn't this distinction also be important here? What is the relationship of SOH(c) to SOH(e)?
And just multiplying 70% SOC(c) with the remaining range seems like a mistake due to the same effect.
Could you explain it here as a comment? Thank you!

[waleedaftab]

I have a Li-ion battery say 10AH. How can i estimate its state of health. is this possible, then how?

[robertobasf]

Hi, how the vehicle calculate the ESR along the time to evaluate the SOH?

[PavolFilek]

SOH for capacity and for impedance is not one static value. If you have temps. range -15 - 60 *C and capacity 300 Ah and you want to calculate SOH, you have to calculate / 60 - ( -15 ) x 300 === 22500 point LUT / look up table /, because for each SOC and temp, impedance is different number.

[ncm]

I hope you can create a video, on recommending when to change a 12v lead acid battery. what is the critical SOH threshold that i can still charge my car battery and stretch my wallet further before i change a new car battery

[virtualdrive]

Am I the only one here who feels that Stafl looks like 'Bruce Banner' from the movie 'The Incredible Hulk' ? :)

[shaharukhkhan]

Please conform battery charge ecplain soc