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Installation, commissioning and operating instructions for valve-regulated stationary lead-acid batteries
7140203153 V1.4 (09.2018)
Installation, commissioning and operating instructions for valve-regulated stationary lead-acid batteries
7140203153 V1.4 (09.2018)
6.2.5 Equalizing charge (correction charge)
Under normal circumstances equalizing charges are not required.
If there are unacceptably large discrepancies between the cell voltages of the individual cells at float charge
(see Tab. 6–3)
, an equalizing charge must be performed.
Equalizing charges are necessary after exhaustive discharges, after inadequate charging, if the cells have been
held at non-uniform temperatures for long periods of time or if the voltage value of one or more cells has drop-
ped below the critical threshold as specified in
Tab. 6–3
during operation.
Type
Float charge voltage
OPzV, power.bloc OPzV, net.power 12 V 100 und 12 V 150Ah,
grid
| power
VR M
(power.com SB), power.com HC,
sun
| power
VR L
(OPzV
solar.power/OPzV bloc solar.power),
sun
| power
VR M
(solar.bloc)
2.25 V/cell +/- 1%
net.power 12 V 92 and 170 Ah, power.com XC
2.27 V/cell +/- 1%
grid
| power
VR X
/grid
| power
VR X FT
2.28 V/cell +/- 1%
Voltage per unit
2 V
4 V
6 V
12 V
Tolerance float charge
voltage for single cells
(deviation from average
float charge voltage)
-0.10 V/+0.20 V
-0.14 V/+0.28 V
-0.17 V/+0.35 V
-0.25 V/+0.50 V
Tab. 6–3: Float charge voltage
Example for OPzV cells: Float charge voltage max. = 2.45 V/cell and min. 2.15 V/cell (at average float charge
voltage of 2.25 V/cell).
Attention!
As the max. permitted load voltage might be exceeded, it must be clarified in advance whether
the loads can be disconnected for the duration of the equalizing charge.
Perform the equalizing charge as follows:
1. Charging with IU characteristic up to max. voltage U = 2.4 V/cell up to 48 hours. The charge current must
not be higher than 20 A per 100 Ah nominal capacity.
2. If the maximum temperature exceeds 45 °C, terminate the charging process or switch to float charge to
allow the temperature to drop.
3. The end of the equalizing charge is reached when the cell voltage do not rise for a period of 2 hours.
Required process for charging the batteries by achievement of max. storage duration:
Refer to
Chap. 4
.
Note that float charge voltages of lead-acid batteries with electrolytes fixed in gel can fluctuate
significantly within the first four years after initial commissioning. The voltages range in an area
between ca. 2.12 V/cells and 2.5 V/cell +/-1%. The black lines in
fig. 6-4
depict this area of float
charge voltage for the first five years of battery service life. The exact development of the voltage
values can not be determined in advance.
Fig. 6-4
depicts rather the trend of this typical behaviour
and related reasonable alarm thresholds.
Cell Voltage U [V/Cell]
Time [Years]
Background: The scattering of float charge voltages of gel batteries is a normal phenomenon and
has no negative impact on the efficiency or capacity of the battery cells. This voltage scattering
leads to a balanced internal gas recombination within the battrey string with the result of lower
voltage differences and improved cell-internal oxygen and hydrogen recombination rates. This pro-
cess can neither be accelerated through cyclitzation of the battery, nor by raised charge voltages.
The normal equalizing charge voltage leads optimally to a homogeneous gel structure and a high
efficency of the battery over the entire service life.
Fig. 6–4: Trend of float charge voltage over service life of gel batteries.
