19
When the network voltage is higher than the Evolion terminal voltage, the module begins charging. The Evolion re-charges with a
typical constant current/constant voltage (CC/CV) profile. The maximum and recommended re-charge set point is 56.0 Vdc +/- 0.5%.
The temperature compensated voltage control is not necessary. There is no risk of thermal runaway in float operation since there is
no heat producing side reactions. Unlike traditional technologies that accept overcharge current and consume water and generate
hydrogen and oxygen gas, the Li-ion electrochemistry will not accept overcharge current or spill any excess energy after it reaches
a full charge state or even while re-charging in any phase. When it is fully charged to its setpoint voltage (56.0 Vdc = 100 %), no more
current will be accepted by the cells (see Float mode).
During re-charge and until it is fully charged, the Evolion accepts charge current with close to 100 % coulombic efficiency. It is the
same efficiency at all operating temperatures. The maximum SoC it will attain is equal to the set point voltage (see chapter Open
Circuit Voltage (OCV) as a function of State of Charge (SoC)). If the re-charge set point is less than 56 Vdc, the maximum obtained %SoC
of the Evolion will also decrease. It decreases approximately 10 % for each 1 volt less than 56.0 Vdc. The re-charge set-point should
always be higher than 49 Vdc to make sure the cell balancing circuits will remain active during charge operation.
An example of the CC/CV re-charge characteristics is shown in Figure 9. It is the typical characteristics of the fast charge mode using
32 A of re-charge current per module. In this example, the Evolion is fully charged in approximately 3 hours. With 100 % coulombic
charge efficiency, with every 1 Ah re-charged there is 1 Ah of discharge capacity available to be utilized on the next discharge.
8. Charging
Figure 9. The typical CC/CV re-charge characteristics of an Evolion
8.1 Maximum re-charge current (IMR)
The maximum re-charge current (IMR) gives the maximum allowed re-charge current for the fast charge mode. This maximum current
level is defined to optimize the useful life of the Evolion and to ensure safe operation, in particular for frequent cycling applications. Figure
10 illustrates 3 different curves, i.e., IMR, 0.85 x IMR and 0.75 x IMR.
In general, avoiding the charge regulated mode in operation is the best way to guarantee the highest efficiency offered by the Evolion.
If charge regulated mode ever becomes active, a large part of the re-charge energy will be consumed as heat and dissipated on the
front heat sink. To avoid the charge regulated mode, controlling the output current of the rectifier shelf is necessary. Controlling
the output to limit the available re-charge current can be done by either dimensioning the installed rectifier capacity or setting the
re-charge current set point. Use the following as a guide.
Charge time (h)
Unit voltage (V), Current (A)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2
60
54
48
42
36
30
24
18
12
6
0
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
% Available Capacity
Charge Amps
Unit Voltage
Содержание evolion
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