3.2. Charging
3.2.1. Full charge
The full charge is a prolonged charge at an elevated voltage, performed under the supervision of the user. It
lasts until certain full charge criteria are fulfilled but not outside certain minimum and maximum duration limits.
It is used mainly
as Commissioning charge after installation in paragraph 2.7
as Corrective Equalizing charge in paragraph 3.2.2.2
as preparation charge before a capacity test in paragraph 6
as refresh charge during long storage period (in paragraphs 1.2, 7)
During charge, the battery temperature shall be continuously monitored. It should never exceed 45
o
C, otherwise
the charge shall be interrupted for sufficient time to cool down the battery.
Case 1) With external charger of IU - characteristic.
For the commissioning charge the current shall be limited to 0.1*C10 Amps.
Battery
temperature
Voltage settings
Minimum and maximum
charging times
Full charge criteria.
15-30
o
C
2.35 – 2.40 V
36h – 72h
when the individual cell voltages have not
risen for a period of 4 hours.
30-40
o
C
2.32 – 2.35 V
24h - 48h
0-10
o
C
2.38 – 2.45 V
48h - 72h
Case 2) With external charger of IUI or I - characteristic.
Using an IUI or I charger that can charge the battery with constant current at a n elevated voltage, higher than
2.60 Vpc up to 2.80 Vpc.
Bulk
charge
current
limitation
Voltage settings
for U phase
gassing
charge
current limitation
Minimum and maximum
charging
times
at
gassing phase
Full charge criteria
0.2*C10
2.33 – 2.40 V
0.012*C10
(1.2 A per
100Ah
nominal capacity)
5h – 8h
when the individual cell
voltages have not risen
for a period of 1 hour.
Case 3) Using the solar controller.
Connect the battery to the controller and leave it for 1-2 weeks while the application load is disconnected. Full
charge criteria are not applicable here. Use the following voltage settings:
On-off controllers
-20 to 0°C
0 to 35°C
>35°C
High disconnect voltage (Vr)
2,55V
2,45V
2,40V
Low restart voltage (Vrr)
2,35V
2,30V
2,25V
Constant Voltage controllers
-20 to 0°C
0 to 35°C
>35°C
Regulation voltage (Vr)
2,45V
2,37V
2,33V
3.2.2. Equalizing
3.2.2.1. Functional Equalizing
During a cycling operation, the target is to achieve an almost complete recharge (100% SOC) after every
discharge cycle otherwise a permanent capacity decrease will threaten the battery’s state of health. This is not
always possible in Stand-alone applications where the RES source depends on the weather conditions and the load
is possible to exceed the expected level. Here, a proper “Array to Load ratio” as given in paragraph 3.1, is critical
for the life expectancy of the battery. For Hybrid systems with diesel generator (e.g. mainly telecom hybrid
systems), the charging source is always available but the boost charging time is restricted to achieve a more
efficient utilization of the diesel. In both cases, a scheduled (functional) equalizing charge shall be given at regular
intervals (see next) to protect the battery from sulphation and lagging cells.
Equalizing frequency is adjusted according to the charge deficit. The less complete the daily recharge is, the
more frequent the equalizing is required.
The charging duration is fixed.
The voltage settings are the same values used for a normal recharge.
3.2.2.2. Corrective Equalizing
Equalizing charges are also required after incidents of excessive stress for the battery (deep discharges with
inadequate charges) or when the individual cell voltages show excessive deviation from the average (lagging cells
