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2.3.1
Charge Efficiency Factor (CEF)
During battery charging, not all of the energy transferred into the
battery is available when the battery is being discharged. The charge
efficiency of a brand new battery is approximately 90%. This means
that 10Ah must be transferred to the battery to get 9Ah actually stored
in the battery. This efficiency figure is called the Charge-Efficiency-
Factor (CEF) and will decrease with battery age. The BMV can
automatically calculate the CEF of the battery.
2.3.2
Peukert's exponent
As mentioned in chapter 1.3, the Peukert efficiency describes how,
when you discharge a battery faster than the 20hr rating, its Ah
capacity decreases. The amount of battery capacity reduction is called
the 'Peukert exponent' and can be adjusted from 1.00 to 1.50. The
higher the Peukert exponent the faster the battery size shrinks with
increasing discharge rate. An ideal (theoretical) battery has a Peukert
Exponent of 1.00 and has a fixed capacity; regardless of the size of the
discharge current. Of course such batteries do not exist, and a setting
of 1.00 in the BMV is only implemented to bypass Peukert
compensation. The default setting for the Peukert exponent is 1.25,
and is an acceptable average value for most lead acid type of
batteries. However for precise battery monitoring, entering the right
Peukert exponent is essential. If the Peukert exponent is not provided
with your battery, you can calculate it by using other specifications
which should be provided with your battery.
The Peukert equation is stated below:
n
where the Peukert exponent, n =
Cp
I
t
=
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