JLG X390AJ-X14J Supplement Manual page 100

SECTION 3 - TROUBLESHOOTING AND FAULT CODES
Second Group - Cell Voltage (mV)
1. Delta (mV): It is the difference between the highest cell
and lowest cell (mV).
Discharge phase: The cells supply the same level
of current as when they are connected in series.
For this reason, the cells should have the same
voltage drop and the voltage difference should
be below 150 mV (100 mV on 1st generation
BMS). If Delta (mV) value during the discharge
increases more than 250 mV (200 mV on 1st gen-
eration BMS), it is necessary to discharge and
recharge the battery pack completely and check
the value again.
Charging phase: Delta (mV) value during the
charge operation is an important data for the
diagnosis. During the charge, this value can
increase to more than 400 mV. However at the
end of the equalization operation it should be
approximately 100 mV (50 on 1st generation
BMS) or in any case fluctuating to 250 mV or less
(this will not be due to a machine problem).
To make sure that the system is well equalized, it
is recommended to periodically leave the
machine under charge for at least one night. If
the Delta (mV) value is not decreasing below
250 mV even after charging for one night, it is
necessary to check which cell is the highest one,
completely discharge and recharge the system
and check again.
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2. Lowest - at: It is the voltage at the lowest cell.
MAF12260
The number of the corresponding cell is indi-
cated on side.
During the charge: As the lithium cells do not
have the same characteristics at 100%, even
when they are charged with the same current
level, it is possible that one cell reaches the max-
imum charge level quicker than the other cells.
This characteristic is normal and it does not
mean that there is a failure. However, at the end
of the charging process, if the lowest cell is
always the same, its value should be approxi-
mately 3450 mV.
During the Discharge: During the discharge, the
cells voltage should decrease in the same way,
so the Delta (mV) value should decrease. If one
cell voltage decreases quickly compared to the
other cells, this can be a defective cell.
For example, if the highest cell is at 3.3 Volt, and
the lowest cell is at 2.8 Volt, there is possibility of
a problem. In this case, it is important to analyze
the value "average", because it shows if the other
cells are closer to the higher cell or to the lower
cell showing where the problem is.
If only one cell in a battery pack is replaced after
many years, this new cell will decrease voltage
slowly than other cells, but the BMS can control
that characteristic.
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