Environmental Engineering Reference
In-Depth Information
Statistics of P ( V ) are summarized in Table 4.6. Note that for this battery pack
(SE = 92 Wh/kg) and the energy consumption computed as 156 Wh/mi, we find
that for a swing of 70% SOC depletion on a 28 kWh pack results in a nominal all
electric range (AER) of
E batt d SOC
E mi ¼
28,000 ð 0 : 7 Þ
156 ¼ 125mi
AER ¼
ð 4 : 5 Þ
Note that Elite Power Solutions advertises the vehicle as having 100 mi AER,
and that the 137 mi trip from Flagstaff to Phoenix, AZ was completed on a single
charge. So, the nominal AER computed in (4.5) is realistic for a fresh battery pack.
With ageing the pack energy will diminish as will AER and eventually diminish to
the advertised 100 mi value.
Table 4.6 Summary of vehicle level simulation
Parameter
Description Value Parameter
Description
Value
UDDS avg. speed
V (mph)
19.6
Motoring power
P mot (KW pk )
28.5
UDDS max speed
V mx (mph)
56.7
Regeneration power
P regen (KW pk ) 21.2
Distance per cycle mi
7.44
Average power
P avg (kW)
1.657
4.2.2 Step 2
For dynamic simulation the Maxwell ultra-capacitor model is used and a functional
representation of the lithium ion battery is developed. For this representation the dis-
charge and charge characteristics of the lithium-iron-phosphate (LFP) cell are approxi-
mated as shown in Figure 4.10. Note that for a 44 cell string that is at 5% SOC, the
terminal voltage drops to 110 V, or the cut-off potential of 2.5 V/cell is recommended.
For this application, the converter used is either the half-bridge dc/dc converter
or more commonly the bidirectional buck-boost converter as shown in Figure 4.11.
Battery characteristic for GBS 200 Ah
150
147.996
U b ( i )
144.286
138.571
132.857
127.143
121.429
115.714
110.071
110
90
80
70
60
50
40
30
20
10
0
100
SOC(i)
0
Figure 4.10 Representative 200 Ah, 3.2 V 44 LFP battery characteristic used in
simulation
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