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8
6.5 – Battery Sizing Graphs
These graphs can be used to determine the required
battery capacity and the resulting RECOVERY time
for the system.
Figure 6.5.1 – Battery Capacity vs. Average Load Current & Hold-up Time
1000
800
400
200
100
80
40
20
10
8.0
4.0
2.0
1.0
0.1
0.2
Figure 6.5.2 – Recovery Time vs. Average Load Current & Battery Capacity
80
70
60
50
40
30
20
10
0
0
50
0.4
0.8 1.0
Average Load Current (Amps)
EP
24-5
100
150
200
Battery Capacity (Ah)
RECOVERY time is the time required for the battery
to recover a full state of charge. RECOVERY occurs
while the load is drawing full current. In lightly
loaded systems, the RECOVERY time may be much
less.
Battery
Capacity
384 Ah
272 Ah
192 Ah
136 Ah
96 Ah
68 Ah
48 Ah
34 Ah
24 Ah
17 Ah
2.0
4.0
8.0
EP
12-10
250
300
350
To determine the minimum
required Battery Capacity:
1. Draw a vertical line
through the Average
Load Current.
2. Draw a horizontal line
through the desired
HOLD-UP Time.
3. Mark the intersection.
4. Find the next Battery
Capacity line above the
intersection and read the
value at the right.
Note: This graph has a 1.5
Safety Factor built in.
To determine the maximum
RECOVERY time:
1. Draw a vertical line
through the Battery
Capacity.
2. Mark where this line
intersects the line for the
model of EP.
3. From this intersection,
read the value at the left.
Note: This graph has a 1.2
Safety Factor built in.
400
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