tbs electronics Expert Modular, Owner'S Manual

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34
Practical information
Typically, the midpoint deviation is smallest when the battery bank is not being charged or
discharged. However, even with only healthy batteries in the series string, a temporary imbalance
will occur:
•
during the absorption charge stage
•
when the battery bank is being deeply discharged
•
when the battery bank is exposed to very high charge- or discharge currents
Under these conditions, the midpoint alarm may trip. For this reason the default alarm On delay is
set to 300 seconds, as this is still considered a short enough time to not damage the batteries. The
default setting for the maximum deviation percentage (for formula see
1)
) is 2%, which is considered
a good value for 24V systems. For 48V systems, this percentage should be around 1%. Despite these
default settings, the user should still accept an occasional alarm during the three above mentioned
conditions.
In case the midpoint alarm trips frequently or unexpectedly, one or more batteries or cells may be
dying or reaching their end of life. The batteries or cells should be measured individually with a Volt
meter to find the potentially defect battery. In case of paralleled series strings, please make sure to
remove the midpoint interconnection cable(s) first before measuring the individual batteries.
!
Since there are too many variables involved, TBS assumes no responsibility or liability
for battery damage or costs which might arise out of the use of the midpoint voltage
alarm. This functionality should only be used by experienced installers with sufficient
battery knowledge and is intended for global indication purposes only.
1)
d = 100 *
(V2−V1)
Vavg
where:
d = deviation in %
V2 = voltage of the upper half in the series string
V1 = voltage of the lower half in the series string
Vavg =
(V1 + V2)
2