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Nick RPh625
How do you calculate the battery degradation based on number of...
The battery degradation comes from cyclic and calendar aging. The cyclic aging normally accounts for the C-rate, temperature, DoD usage and No. of cycles. On the other hand, the calendar aging takes into account the SOC, temperature and time. There is no formula as such for the battery degradation calculation. You just measure the capacity/energy difference between a fresh cell and aged cell as a factor of the no. of cycles/ years to quantify the degradation. For instance, a fresh cell gives a discharge capacity of 5 Ah for a 100% DOD at 25 deg C and 1C charge/discharge. Now you cycle the cell for 100 cycles at the same condition and measure the capacity. Let us assume you get a capacity of 4 Ah. Now you calculate the degradation as a function of State of Health (SOH).
SOH = (Initial capacity - measured capacity after 100 cycles)*100/ Initial capacity = (5-4)*100/5 = 20% So, you have a degradation of 20%. *Note: 100 in the equation denotes percentage.
Please note that aging calculation is not this straight forward in real life. Because, the aging parameters (C-rate, DOD, temperature, time etc.) are not constant across the usage of the batteries.
The battery degradation comes from cyclic and calendar aging. The cyclic aging normally accounts for the C-rate, temperature, DoD usage and No. of cycles. On the other hand, the calendar aging takes into account the SOC, temperature and time. There is no formula as such for the battery degradation calculation. You just measure the capacity/energy difference between a fresh cell and aged cell as a factor of the no. of cycles/ years to quantify the degradation. For instance, a fresh cell gives a discharge capacity of 5 Ah for a 100% DOD at 25 deg C and 1C charge/discharge. Now you cycle the cell for 100 cycles at the same condition and measure the capacity. Let us assume you get a capacity of 4 Ah. Now you calculate the degradation as a function of State of Health (SOH).
SOH = (Initial capacity - measured capacity after 100 cycles)*100/ Initial capacity = (5-4)*100/5 = 20% So, you have a degradation of 20%. *Note: 100 in the equation denotes percentage.
Please note that aging calculation is not this straight forward in real life. Because, the aging parameters (C-rate, DOD, temperature, time etc.) are not constant across the usage of the batteries.
Well, I just meant that there is no straight forward formula to just plug the inputs and derive the outputs for capacity degradation. That is what I meant by 'No formula'. Of course, you can always build an ECM or semi-empirical models to calculate the non-linear behavior of batteries to calculate the capacity loss, not to mention the complexity of resistance increase coupled with capacity fade and the quantification of cyclic and calendar degradation.
All I meant was, there is no simple answer for capacity degradation number. In real life we can't measure the capacity difference after certain number of cycles by just charging/ discharging (RPT). No BMS is capable of doing it. We rely on look up table and equation based algorithm and that's where the models come into picture.
About the normalization of the capacity, I was just giving a simple example assuming the question is simple about the calculation of capacity loss in a typical charge/discharge test for a certain number of cycles.
Well, I just meant that there is no straight forward formula to just plug the inputs and derive the outputs for capacity degradation. That is what I meant by 'No formula'. Of course, you can always build an ECM or semi-empirical models to calculate the non-linear behavior of batteries to calculate the capacity loss, not to mention the complexity of resistance increase coupled with capacity fade and the quantification of cyclic and calendar degradation.
All I meant was, there is no simple answer for capacity degradation number. In real life we can't measure the capacity difference after certain number of cycles by just charging/ discharging (RPT). No BMS is capable of doing it. We rely on look up table and equation based algorithm and that's where the models come into picture.
About the normalization of the capacity, I was just giving a simple example assuming the question is simple about the calculation of capacity loss in a typical charge/discharge test for a certain number of cycles.
Yet, the initial question "If we know the number of cycles i.e. charging and discharging how do we calculate the degradation from this." Can't be answered solely by the the cycles.
Also your definition of State of Health assumes a normalization for the whole capacity range which is not that common. It is more common to normalize the state of health to e.g. 70% or 60% remaining capcity (e.g. 0% SOH == 60% remaining capacity).
Yet, the initial question "If we know the number of cycles i.e. charging and discharging how do we calculate the degradation from this." Can't be answered solely by the the cycles.
Also your definition of State of Health assumes a normalization for the whole capacity range which is not that common. It is more common to normalize the state of health to e.g. 70% or 60% remaining capcity (e.g. 0% SOH == 60% remaining capacity).
The battery degradation comes from cyclic and calendar aging. The cyclic aging normally accounts for the C-rate, temperature, DoD usage and No. of cycles. On the other hand, the calendar aging takes into account the SOC, temperature and time. There is no formula as such for the battery degradation calculation. You just measure the capacity/energy difference between a fresh cell and aged cell as a factor of the no. of cycles/ years to quantify the degradation. For instance, a fresh cell gives a discharge capacity of 5 Ah for a 100% DOD at 25 deg C and 1C charge/discharge. Now you cycle the cell for 100 cycles at the same condition and measure the capacity. Let us assume you get a capacity of 4 Ah. Now you calculate the degradation as a function of State of Health (SOH).
SOH = (Initial capacity - measured capacity after 100 cycles)*100/ Initial capacity
= (5-4)*100/5
= 20%
So, you have a degradation of 20%.
*Note: 100 in the equation denotes percentage.
Please note that aging calculation is not this straight forward in real life. Because, the aging parameters (C-rate, DOD, temperature, time etc.) are not constant across the usage of the batteries.
Hope this helps.
The battery degradation comes from cyclic and calendar aging. The cyclic aging normally accounts for the C-rate, temperature, DoD usage and No. of cycles. On the other hand, the calendar aging takes into account the SOC, temperature and time. There is no formula as such for the battery degradation calculation. You just measure the capacity/energy difference between a fresh cell and aged cell as a factor of the no. of cycles/ years to quantify the degradation. For instance, a fresh cell gives a discharge capacity of 5 Ah for a 100% DOD at 25 deg C and 1C charge/discharge. Now you cycle the cell for 100 cycles at the same condition and measure the capacity. Let us assume you get a capacity of 4 Ah. Now you calculate the degradation as a function of State of Health (SOH).
SOH = (Initial capacity - measured capacity after 100 cycles)*100/ Initial capacity
= (5-4)*100/5
= 20%
So, you have a degradation of 20%.
*Note: 100 in the equation denotes percentage.
Please note that aging calculation is not this straight forward in real life. Because, the aging parameters (C-rate, DOD, temperature, time etc.) are not constant across the usage of the batteries.
Hope this helps.
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Well, I just meant that there is no straight forward formula to just plug the inputs and derive the outputs for capacity degradation. That is what I meant by 'No formula'. Of course, you can always build an ECM or semi-empirical models to calculate the non-linear behavior of batteries to calculate the capacity loss, not to mention the complexity of resistance increase coupled with capacity fade and the quantification of cyclic and calendar degradation.
All I meant was, there is no simple answer for capacity degradation number. In real life we can't measure the capacity difference after certain number of cycles by just charging/ discharging (RPT). No BMS is capable of doing it. We rely on look up table and equation based algorithm and that's where the models come into picture.
About the normalization of the capacity, I was just giving a simple example assuming the question is simple about the calculation of capacity loss in a typical charge/discharge test for a certain number of cycles.
Thank you for your comment though.
Well, I just meant that there is no straight forward formula to just plug the inputs and derive the outputs for capacity degradation. That is what I meant by 'No formula'. Of course, you can always build an ECM or semi-empirical models to calculate the non-linear behavior of batteries to calculate the capacity loss, not to mention the complexity of resistance increase coupled with capacity fade and the quantification of cyclic and calendar degradation.
All I meant was, there is no simple answer for capacity degradation number. In real life we can't measure the capacity difference after certain number of cycles by just charging/ discharging (RPT). No BMS is capable of doing it. We rely on look up table and equation based algorithm and that's where the models come into picture.
About the normalization of the capacity, I was just giving a simple example assuming the question is simple about the calculation of capacity loss in a typical charge/discharge test for a certain number of cycles.
Thank you for your comment though.
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Sivarajakumar Maharajan
I do not not agree with your statement "There is no formula as such for the battery degradation calculation".
There are several approximation and models such as by Johannes Schmalstieg et al.
Article A holistic aging model for Li(NiMnCo)O2 based 18650 lithium-...
Yet, the initial question "If we know the number of cycles i.e. charging and discharging how do we calculate the degradation from this." Can't be answered solely by the the cycles.
Also your definition of State of Health assumes a normalization for the whole capacity range which is not that common. It is more common to normalize the state of health to e.g. 70% or 60% remaining capcity (e.g. 0% SOH == 60% remaining capacity).
Sivarajakumar Maharajan
I do not not agree with your statement "There is no formula as such for the battery degradation calculation".
There are several approximation and models such as by Johannes Schmalstieg et al.
Article A holistic aging model for Li(NiMnCo)O2 based 18650 lithium-...
Yet, the initial question "If we know the number of cycles i.e. charging and discharging how do we calculate the degradation from this." Can't be answered solely by the the cycles.
Also your definition of State of Health assumes a normalization for the whole capacity range which is not that common. It is more common to normalize the state of health to e.g. 70% or 60% remaining capcity (e.g. 0% SOH == 60% remaining capacity).
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