090303.03
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Battery watch BW312A / BW324A
Introduction
The Vetus battery watch controls 3 separate batteries (e.g. auxiliary battery, starter battery
and bow prop battery) and ensures that all 3 batteries are being charged
simultaneously
by the engine’s alternator.
By applying a different technology, to that universally used for isolator diodes, the voltage
drop of the Vetus battery watch is significant lower; viz. approx. 0.1 volt at a current of 25
A per diode.
For comparison, an isolator diode usually suffers from a voltage drop of 0.7 Volt. This
means that the charging voltage of the batteries will be 0.7 Volt lower than the output volt-
age of the alternator. The batteries will never be fully charged with this lower charging volt-
age. A battery which is always being charged up to less than 100% will have a very short
service life! Compensation of the alternators charging voltage is required to charge the bat-
teries up to 100%. This required charging voltage compensation is with certain alternators
not easily achieved.
Compensation for the charging voltage is not required in the Vetus battery watch.
Besides the three isolator diodes the battery watch contains the following extras (see also
block diagram):
Voltmeter
By means of Digital LCD voltmeter the voltage of each of the 3 connected batteries will be
displayed automatic by time interval. The respective LED will glow to indicate which bat-
tery voltage is displayed. Also, the switch is provided to hold any of the battery voltage dis-
play.
An under voltage watch
For each of the 3 connected batteries an under voltage is detected by means of a warning
LED and a disconnectable buzzer.
A discharge monitor for the auxiliary battery
If the voltage of the auxiliary battery drops to too low a level the current will automatically
be switched off. The current will be switched on when the voltage recovers.
Excessive discharge of the battery is prevented by this provision. Frequent excessive dis-
charge substantially shortens battery life.
An LED on the operating panel indicates when power is switched on.
A main switch for the auxiliary battery
It is also possible, by means of a switch at the operating panel, to switch on or off easily
the output from the auxiliary battery. Installation of a difficult to get at main switch is no
longer required.
