2022-03-03 00:10:08
K is equal to OCV1-OCV2 divided by t1-t2. 2. The standard deviation
feedback of the pressure drop difference is often used by some Japanese
and Korean companies: △OCVu003eaverage (△OCV)+4.5, judge NG1NG for a
period of time, retest and filter; prompt: The average value (△OCV) is
the average value of △OCV; it is the standard deviation of △OCV. The K
value of a good battery is generally less than 2mV/d or 0.08mv/h.
Important factors affecting the K value are:
1. Positive and negative
electrode materials, electrolyte Type, thickness type of diaphragm:
Since self-discharge mainly occurs between materials, the properties of
materials have a great influence on self-discharge. Someone has done
experiments to prove that the self-discharge of ternary materials is
higher than that of lithium cobalt oxide batteries;
2. Storage time: The
longer the storage time, on the one hand, the absolute value of the
pressure drop will increase; on the other hand, it pretends to reduce
the absolute error/pressure of the instrument. Decrease the value to
make the result more accurate. However, if the storage time is too long,
the capacity balance between the positive and negative electrodes will
gradually break and deepen, and the decomposition of the electrolyte
will also accumulate some irreversible capacity loss, which will
increase the self-discharge. The longer the time, the smaller the k
value.
3. Storage conditions: The increase in storage temperature and
humidity will increase the degree of self-discharge.
4. It is also
related to the self-consumption of the battery protection board.
5. Test
initial voltage: the initial voltage (or primary voltage) is different,
the K value obtained is also different. The higher the initial voltage,
the higher the self-discharge rate; technically speaking, the
self-discharge capacity attenuates, but don’t let the battery discharge
to directly measure the remaining capacity without proper equipment, and
can only measure the self-discharge indirectly by measuring the
voltage. It is the K value. If the variation of the environmental
conditions leads to the deviation of the test voltage, it may cause the K
value measurement error. Even if the actual measurement is negative,
this is obviously inconsistent with the meaning of self-discharge
itself, so the equipment should be checked regularly and the measurement
environment is consistent.
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