Datasheet
PRELIMINARY
UB20.241
U–Series
24V, 20A, DC-UPS
27.3. CONNECTION OF THE CENTER TAP
For optimized battery charging and testing the monitoring of every single battery is necessary. This ensures the
longest service lifetime of the batteries. Therefore it is recommended to connect the centre point of both batteries
with the center tap screw terminal of the UB20-241. (Fig.:26-4)
Fig. 27-4 Typical wiring of the center tap
Fuse
L N PE
+ +
--
Power
Supply
Output 24V
max. 25A
UB20
DC-UPS
+
-
IN
+
-
BAT
OUT
R
e
a
d
y
B
u
f
f
e
rin
g
R
e
p
l
a
c
e
B
a
t
.
In
h
i
b
i
t
+
-
Buffered circuits
Non-buffered
circuits
Center Tap (13)
Data/ Temp. (11)
RTN (12)
Fuse
+-
BAT2
12V
+-
BAT1
12V
+
-
27.4. REFRESH FUNCTION
When there is a long time interval during the battery is not charged, the battery becomes deep-discharged due to
the self discharge rate of lead acid batteries. The batteries cannot be charged with standard charging method and
must be replaced. Therefore the UB20 is equipped with a refresh function. This function can be started and only
works with intelligent battery modules. To avoid overcharging of good batteries or blowing up bad batteries each
battery will be tested. If all tests pass certain criteria, a safe and controlled overcharging of the batteries starts.
This test will be repeated after every refresh process. Maximum 5 refresh cycles per battery are possible. If the battery
cannot refreshed during these cycles the battery will be indicated as defective.
The Refresh process can be interrupted by pulling the optional plug and the power terminal of the battery module
Fig. 27-5 Time schedule of the refresh function
2
30
minutes
1
10s 10s
2121
1 2
21
1 2
21
1
Refresh
phase
Refresh
phase
Test phase
10s
30
minutes
10s
30
minutes
30
minutes
10s
30
minutes
September 2012 / Rev. 1.3 DS-UB20.241-EN preliminary
All parameters are specified at an input voltage of 24V, 20A output load, 25°C ambient and after a 5 minutes run-in time
unless otherwise noted. It is assumed that the input power source can deliver a sufficient output current.
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