Nemo
Member
- Joined
- Apr 26, 2019
- Messages
- 53
For those interested in IR and wanting to know what a "good" IR is for various cells I've put together the following table. This was built from a combination of Wolf, 100kWh Hunter, and my own data. All IR measurements were taken with a 4-wire Kelvin type AC 1kHz impedance tester, specifically the YR10XX series. This expands on original work by Wolf, so credit for the idea goes to him.
The values have been derived from a linear best fit line of all measuredremaining capacities greater than 70% for each type of cell. There is still noise within this data, so optimal IR has been defined as the IR which correlates 85% remaining capacity according to the trendline. Marginal Capacity is defined as the IR which correlates 75% remaining capacity according to the trendline. This means that you are likely to achieve 80% remaining capacity if you measure the IR to be equal to or less than the optimal IR. And there's a chance you will achieve it if IR falls between optimal and marginal IR. If the IR reading is above the marginal IR value you are unlikely to achieve 80% remaining capacity.
The hope is that this will save harvesters a lot of time by allowing them to focus on testing the cells with the greatest chance of success. Also, if purchasing tested secondhand cells, be sure to ask about IR measurements and ensure they are good!
Thank you very much to Wolf and 100kWh Hunter for sharing their data. If you like this information and want to contribute, I will accept data collected using reasonably accurate charges (equivalent or better than OPUS) and IR readings from a YR10XX type AC impedance meter or equivalent. The more data, the better the results.
If you'd like to view the source file it is available on my google drive under "Cell IR Database"
The values have been derived from a linear best fit line of all measuredremaining capacities greater than 70% for each type of cell. There is still noise within this data, so optimal IR has been defined as the IR which correlates 85% remaining capacity according to the trendline. Marginal Capacity is defined as the IR which correlates 75% remaining capacity according to the trendline. This means that you are likely to achieve 80% remaining capacity if you measure the IR to be equal to or less than the optimal IR. And there's a chance you will achieve it if IR falls between optimal and marginal IR. If the IR reading is above the marginal IR value you are unlikely to achieve 80% remaining capacity.
The hope is that this will save harvesters a lot of time by allowing them to focus on testing the cells with the greatest chance of success. Also, if purchasing tested secondhand cells, be sure to ask about IR measurements and ensure they are good!
Thank you very much to Wolf and 100kWh Hunter for sharing their data. If you like this information and want to contribute, I will accept data collected using reasonably accurate charges (equivalent or better than OPUS) and IR readings from a YR10XX type AC impedance meter or equivalent. The more data, the better the results.
If you'd like to view the source file it is available on my google drive under "Cell IR Database"