Victron energy VBC 12-24-48V Manual page 14

5 hr rating
20 hr rating,
log
Peukert exponent, n =
log
When no ratings are given at all, you can measure your battery using a
constant load bank. In this way a second rating can be obtained, together
with the 20 hr rating which represents the rated battery capacity in most
cases. This second rating can be determined by discharging a fully
charged battery with a constant current; until the battery reaches 1.75 V
per cell (which is 10.5 V for a 12 V battery or 21 V for a 24 V battery). A
calculation example is shown below:
A 200 Ah battery is discharged with a constant current of 20 A and after
8.5 hours 1.75 V/cell is reached.
t =
So,
1
I =
1
20 hr rating,
log
Peukert exponent, n =
log
A Peukert calculator is available at www.victronenergy.com.
10
C = 75 Ah
5 hr
= 5
t hr
1
75 Ah
I = = 15 A
1
5 hr
C = 100 Ah (rated capacity)
20 hr
t = 20 hr
2
100 Ah
I = = 5 A
2
20
hr
20 − log 5
= 1.26
15 − log 5
8 5 . hr
20 A
C = 200 Ah
20 hr
t = 20 hr
2
200 Ah
I = = 10 A
2
20 hr
20 − log 8 5 .
= 1.23
20 − log 10