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13 ADDITIONAL INFORMATION
13.1 BATTERY ALARM FUNCTION
The MasterShunt continuously monitors the batteries
State Of Charge (SOC). If the SOC drops below a
pre-set value or the battery voltage is either too high
or too low, the alarm function is activated.
For alarm functions refer to chapter 9.
13.2 CHARGE EFFICIENCY FACTOR (C.E.F.)
Every battery has a total efficiency. This means that
there must be more Ah charged into the battery than
can be consumed. This ratio is expressed by means
of the Charging Efficiency Factor (CEF). It is used to
correct the calculation of the consumed Amphours
and the time remaining function.
If an efficiency of 70 % has been reached, it will
mean that the battery is at the end of its lifetime and
needs to be replaced.
The CEF is continuously recalculated by the
MasterShunt itself (after two recharges up to 100%
with a proceeding discharges of at least 5%). This
recalculated value is used for new calculations of the
Amphours, the time remaining and the SOC.
13.3 PEUKERT EXPONENT
Standard batteries are rated for a 20-hour discharge.
This means that a 100 Ah battery can supply 5
Amps for 20 hours before a voltage of 1,75 V/cell
(i.e. 10.5V for 12V batteries / 21.0V for 24V /42.0V
for 48V batteries) is reached. If the discharge current
is higher, for example 10 amps, the battery will not
be able to supply the full 100 Ah. In this case the
voltage of 1,75 volt/cell or 10.5/21.0/42.0V is
reached before the battery has supplied its full 20-h
rated capacity. The maximum time battery use time
in the example is approx. 8 hour i.e. 80 Ah.
The Peukert equation is C
C
= battery capacity available with the given
p
discharge current; I = discharge current level;
t= battery discharge time (in hours);
n = Peukert exponent = (logT2–logT1)/(logI2–logI1)
with T1,2 = battery discharge time 1,2
I1,2 = discharge current level 1,2
It describes the effect of different discharge rates on
battery capacity. It can be used to calculate the real
available capacity of a battery, if it is used above or
below its 20 h rating. This equation is also used by
the MasterShunt to calculate the time remaining
function and SOC.
Normally it is not necessary to change the Peukert
exponent. See chapter 11 to adjust the Peukert
exponent.
EN / MasterShunt / February 2011
n
= I
t in which
p
13.4 STATE OF CHARGE (SOC)
The state of charge is expressed as a percentage.
This value is automatically compensated by the
charge efficiency factor (C.E.F.) and the Peukert
exponent. When the battery is fully charged, the
State of charge will be reset to 100%. A battery is
considered to be fully charged if conditions 1 and 2,
1 and 3 or 1 and 4 are met:
1
Parameters below are met for at least 30
seconds:
•
All of the Ah's discharged are charged back
into the battery (real counting without CEF)
•
The actual charge current is less than the
setting for charge amps for full battery.
2
For at least 4 hours the actual battery voltage is
higher than the float voltage plus 1.0/2.0/4.0V(at
nominal battery voltage 12/24/48V)
3
For at least 8 hours the actual battery voltage is
higher than the float voltage plus 0.3/0.6/0.9V (at
nominal battery voltage 12/24/48V)
4
For at least 12 hours the actual battery voltage is
higher than the float voltage minus 0.1/0.2/0.3V
(at nominal battery voltage 12/24/48V).
13.5 AMP = FULL
This value represents the charge current below
which the battery is considered to be fully charged,
provided the float voltage (see chapter 11) is met as
well. The percentage expresses this charge current
related to the battery capacity (C20). Example: If the
battery capacity is 200Ah, and this percentage is set
to 2.0%, the battery is considered to be fully charged
when the charge current has dropped below 200 x
2.0%,= 4 Amps. An older battery (beyond its normal
lifetime) might start to consume more current when it
is fully charged. Setting this value higher may be
usable for old batteries which are beyond their
economical life but have not been replaced yet.
13.6 REPLACEMENT OF BATTERIES
Refer to chapter 5 (Installation) if you want to
replace the batteries.
If new batteries are installed, the historical data of
the old batteries needs to be erased to leave only
historical data from the newly installed batteries. See
chapter 11 for information how to reset the setup.
Contact your Mastervolt dealer if you have a 5 year
system warranty. If necessary, do not forget to
change the setting of the nominal capacity.
ADDITIONAL INFORMATION
21
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