I was working on an A123 battery module with 22S3P configuration. The battery terminal voltage takes really long to settle down to a value in accordance with it's SOC.
Usually, for other chemistries of lithium ion that I worked with, have short relaxation like 30 to 90 minutes. But the A123 module took 15 hours to settle to 62.19V from 60.62V after a short duration of discharge.
Maybe someone from a materials level knowledge could answer or guide me towards the right path?
This would mean the time constants for the internal impedance is very high. My experimental results suggests that the largest time constants is almost 3 hours. Isn't that too much, even considering low conductivity of LiFePO4?
Li diffusion induced elastic and plastic stress (LFP) results in (a farther) low[1] (electronic & Li+) conductivity S. Also, S decreases upon cycling number[1,2] N. Khalid Khan: your (battery) notes are from a used (N>>10 ?) module ?
1. In-situ characterization of strain in lithium battery working electrodes http://www.sciencedirect.com/science/article/pii/S0378775314012907
2. Electron microscopy investigations of changes in morphology and conductivity of LiFePO4/C electrodes http://ac.els-cdn.com/S037877531530731X/1-s2.0-S037877531530731X-main.pdf?_tid=afe60e36-9edf-11e6-8bce-00000aab0f26&acdnat=1477859604_47bc483d9805a68b57822153dfd3a7bd
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