Victron energy Blue Power BMV-602, Manual

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6
The battery specifications needed for calculation of the Peukert
exponent, are the rated battery capacity (usually the 20hr discharge
rate
1
) and for example a 5hr discharge rate
2
. See below for an
example of how to define the Peukert exponent using these two
specifications.
5hr
rating
20hr
rating,
1.26
1.26 1.26
1.26
=
−
−
=
5 log 15 log
5 log 20 log
exponent, Peukert n
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 20hr 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 1.75V 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:
1
Please note that the rated battery capacity can also be defined as the 10hr or even 5hr discharge rate.
2
The 5hr discharge rate in this example is just arbitrary. Make sure that besides the C20 rating (low discharge current) you choose a second rating
with a substantially higher discharge current.
A
hr
Ah
I
hr t
Ah C
hr
15
5
75
5
75
1
1
5
= =
=
=
A
hr
Ah
I
hr
Ah C
hr
5
20
100
20 t
capacity) (rated 100
2
2
20
= =
=
=