Battery-Monitor BLS
REV 1A – APR 2019 - Software Version 1A page 16
5.2 Function of battery capacity calculation
Here are some notes on the function of the battery capacity calculation.
5.2.1 Detection of full charge
A battery is considered fully charged (100%) if the following conditions are met, depending on the
type of battery [GEL, ACID, AGM, Lithium].
e.g. for lead acid batteries:
1) the charging voltage is maintained (13.4 V) and
2) the charging current has dropped below 2% of the set battery capacity and
3) the charged capacity is greater than the previous withdrawn capacity.
or
1) the charging voltage is maintained (14.0 V) and
2) the charging current has fallen below 1% of the set battery capacity
If the parameters are met for 3 minutes, the value for the current capacity is reset to 100%. For the
other battery types, values adapted to the battery chemistry apply.
5.2.2 Detection of the unusable portion of battery capacity
If the battery voltage prematurely falls below certain voltage thresholds depending on the load, the
charge state is automatically set to 20% or, if fully discharged, to 0%.
If possible, the unavailable capacity (difference between nominal
capacity and withdrawn capacity) is determined and displayed as a gray
area.
This gray area can be used as an indicator for the aging of the battery
during normal discharges of less than C10 (current less rated capacity /
10).
For high current loads in the range above C5 (e.g., electric boats (current
greater than rated capacity / 5)) this should be taken as an indicator of the usual reduced capacity
at high loads.
Unavailable capacity detection is only possible if the battery has reached the first discharge limit
(depending on battery type & load, below approx. Battery voltage <11.5 V)
If the battery is never discharged to this first discharge limit, this detection can not take place and it
is assumed that the battery is 100% intact.
We therefore recommend that you do this once a year at the start of the season to determine the
performance of the battery system.
5.2.3 Remaining time calculation
The remaining time is the time that the main battery can still be used with the current power
consumption until the capacity alarm is reached.
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