UB40.241
UB-Series
24V,
40A,
DC-UPS
Jun. 2020 / Rev.0.1 DS-UB40.241-EN All values are typical figures specified at 24Vdc input voltage, 40A output current in
power supply mode at 25°C ambient, no charging and after a 5 minutes run-in time unless otherwise noted.
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23.2.
B
ATTERY
R
EPLACEMENT
I
NTERVALS
There are two main causes for battery failures and the need for replacing them:
-
Random failures:
Within the defined service life of a battery, random battery failures can happen. E.g. short circuit in one cell, broken cell connection,
acid pollution, mechanical defects, etc. Such failures occur randomly and cannot be predicted. The device has various battery test
features included, which periodically test both batteries individually and report such failures. These battery tests include:
- Battery presence test, performed every minute
- Battery dynamic impedance test, performed every 4hours. Please not that the first test starts earliest 1 minute after applying the
input voltage.
- Extensive longer charging time test when charging time exceeds 19h in 12Ah setting, 27h in 26Ah , 42h in 36Ah, 32h in 65Ah, 72h in
100Ah and 120h in >150Ah setting
Battery tests start as soon as the batteries are fully charged (the green status LED must be on solid). Battery dynamic impedance tests
need to fail several times in a row before “replace battery” is reported.
This can take up to 14 additional hours after the batteries are
fully charged.
- Wear-out failures:
The electrical characteristics of batteries degrade slowly over time. Main causes are chemical effects, which can be calculated.
Therefore, battery manufacturers specify the design life of batteries to be able to calculate the expected service time. The
degradation of a battery cannot be easily tested on a running system. Therefore, in addition to the results from the battery tests of
the device (random failures), a periodical replacement is strictly recommended.
Service and design life of a battery:
Batteries have a limited service life and need to be replaced periodically. The service life depends on the grade of the battery, which is
expressed in the design life. The design life figures can be found in the individual datasheets of the batteries and is usually specified
according to the Eurobat guideline.
The design life is the estimated life,
based on laboratory condition, and is quoted at 20°C using the manufacturer’s recommended float
voltage condition. According to the Eurobat guideline, design lives have been structured into the following different groups:
3 - 5 years:
This group of batteries is very popular in standby applications and in small emergency equipment.
This represents a 4 years design life with a production tolerance of ±1 year.
6 - 9 years:
This group of batteries is usually used when an improved life is required.
This represents a 7.5 years design life with a production tolerance of ±1.5 years.
10 - 12 years:
This group of batteries is used when in applications where longest life and highest safety level are required. This
represents a 11 years design life with a production tolerance of ±1 year.
If the operational parameters differ from those which are specified for the design life, an earlier replacement of the battery might be
neces
sary. The “real life” is called service life and is defined as the point at which the cell’s actual capacity has reached 80% of its
nominal capacity. At the end of the service life the capacity degrades much faster, so that a further use of the battery is not
recommended.
The degradation of a battery begins with the production date and not with the time when usage starts.
Effects, which shortens the service life of the battery and requires an earlier battery replacement:
- Temperature:
The temperature has the biggest impact in the service life. The higher the temperature, the earlier the wear-out phase of the battery
begins. The wear-out results in a degradation of battery capacity. See Fig. 23-2 for details.
- Number of discharging cycles:
The number as well as the depth of discharging cycles is limited. A replacement of the battery might be necessary earlier than the
calculated service life if the battery exceeds the numbers and values of Fig. 23-3.
- Overcharging and deep discharging:
Overcharging and deep discharging shortens the service life and should be avoided. Due to the two individual battery chargers and
