SIEMENS
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Siemens KT 10.1 · 2016
11
SITOP DC UPS uninterruptible power supplies
DC UPS with battery modules
SITOP DC UPS
■
Technical specifications
The table shows the maximum buffering times for the battery
modules for different load currents.
The SITOP Selection Tool offers detailed selection guidance
according to criteria such as the required backup time, load
current, peak current and battery connection threshold:
Important information for selecting the battery capacity:
Determination of the mains buffering times is based on the dis-
charge period of new or non-aged, completely charged battery
modules at a battery temperature not below +25 °C to the shut-
down of the DC UPS.
Battery aging
reduces the still available battery capacity up until
the end of the service life to typically around 50% of the original
capacity value when new (1.2 Ah/3.2 Ah/7 Ah, etc.) and the in-
ternal resistance increases. When the message "Battery charge
> 85%" appears, only around 50% x 85% = approx. 43% of the
originally available capacity can be assumed at the end of the
battery service life.
At battery temperatures below +25 °C, the available capacity
drops approximately by another 30% at +5 °C battery tempera-
ture, to approximately 70% of the approximately remaining 43%.
There is then only around 30% of the original capacity available.
A significantly larger battery capacity must therefore be selected
when configuring the plant: A drop to approx. 50% is compen-
sated for by selecting 1 / approx. 0.5 = approx. double the
battery capacity (required as per the table for the relevant load
current and the relevant buffering time). Available capacity
of approx. 43% is compensated for by selecting 1 / approx.
0.43 = approx. 2.33 times the battery capacity. Available capac-
ity of approx. 30% is compensated for by selecting 1 / approx.
0.3 = approx. 3.33 times the battery capacity.
Recommendation:
Instead of installing double the battery capacity, regular battery
replacement halfway through the expected service life (reduc-
tion of capacity to approx. 50%) can be more advisable for the
following reasons: Capacity does not drop below 100% until the
halfway point of the expected battery life (or slightly beyond).
With regular replacement after this point, only the single battery
capacity (instead of double capacity) must be installed due to
aging (-> neutral in price with regard to battery module costs,
but only requires half the space).
Replacing the battery after half its service life dispenses above
all with the large scatter range of the residual capacity at the end
of the service life, which is not accurately defined by battery
manufacturers (after the full time, many batteries are above, but
many are also below the average 50% residual capacity, that is
to say, even if double the capacity is installed, the influence of
aging at the end of service life is not reliably compensated for,
rather only typically) -> When replacing after half the expected
service life, the configured buffering time is maintained with
considerably greater reliability.
In the case of batteries stored in cool conditions (not above
+25 °C) and for not longer than approximately 4 months, the
following service life can be assumed, strongly dependent on
battery temperature:
In normal cases (installation in the coolest location in the control
cabinet at approx. +30 °C), the battery should be replaced with
single installed battery capacity in accordance with the selection
table after 1 year of operation!
•
On the DC UPS module 40 A, at least 2 battery modules of
7 Ah or higher must be connected in parallel for output
currents > 30 A. When connecting battery modules in parallel,
you must ensure identical capacity and aging.
•
After a power failure, the battery module is disconnected from
the loads at the end of the selected buffering time either
automatically or electronically by opening the On/Off control
circuit, and as soon as the 24 V input voltage is available
again, it is quickly re-charged with the charging current of the
relevant DC UPS module (with I-U charge characteristic:
First constant current I for fast charging, and changeover to
constant voltage U to maintain the charge when the battery
is almost full).
Load current
Battery module 1.2 Ah
(6EP1935-6MC01)
Battery module 3.2 Ah
(6EP1935-6MD11)
Battery module 7 Ah
(6EP1935-6ME21)
Battery module 12 Ah
(6EP1935-6MF01)
Battery module 2.5 Ah
(6EP1935-6MD31)
1 A
34.5 min
2.6 h
5.4 h
9 h
2 h
2 A
15 min
1 h
2.6 h
4.6 h
1 h
3 A
9 min
39.3 min
1.6 h
2.9 h
37.5 min
4 A
6.5 min
27.1 min
1.2 h
2.2 h
27 min
6 A
3.5 min
17.5 min
41 min
1.2 h
17.6 min
8 A
2 min
12.1 min
28.6 min
53.3 min
12.5 min
10 A
1 min
9 min
21.8 min
43.5 min
8.8 min
12 A
-
7 min
17.3 min
33.3 min
6.8 min
14 A
-
5 min
15.1 min
27.5 min
5.1 min
16 A
-
4 min
12.5 min
23.8 min
4.3 min
20 A
-
1 min
9.1 min
20.1 min
-
25 A
-
-
-
12.6 min
-
30 A
-
-
-
9.1 min
-
35 A
-
-
-
17.1 min. (2 x 12 Ah)
-
40 A
-
-
-
13.5 min. (2 x 12 Ah)
-
Battery
temperature
Drop to approx.
50% of residual
capacity
Recommenda-
tion: Replace
(at 100% of
residual
capacity) all
Alternative
recommendation
+20 °C
4 years
2 years
+30 °C
2 years
1 year
+40 °C
1 year
0.5 years
Install double
capacity and
replace
1 x per year
© Siemens AG 2016