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.
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.
Figure 6.5.1 – Battery Capacity vs. Average Load Current & Hold-up Time
0.1
0.2
0.4
0.8 1.0
2.0
4.0
8.0
24 Ah
17 Ah
34 Ah
48 Ah
68 Ah
96 Ah
136 Ah
192 Ah
272 Ah
384 Ah
1.0
2.0
4.0
8.0
10
20
40
80
100
200
800
400
1000
Average Load Current (Amps)
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.
Battery
Capacity
Figure 6.5.2 – Recovery Time vs. Average Load Current & Battery Capacity
0
50
100
150
200
250
300
350
400
0
10
20
30
40
50
60
70
80
Battery Capacity (Ah)
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.
EP
12-10
EP
24-5
