Owner`s manual

VANNER Incorporated Testing and Troubleshooting
70-Series Power Management System OWNER’S MANUAL
15
Voltage Comparison
VANN-Guard Status
a.
Battery A is lower than Battery B but
within 0.05 volt.
OFF
Stand-by Mode.
The VANN-Guard will not turn ON until Battery A is lower
than Battery B by more than 0.05 volts.
b.
Battery A is lower than Battery B by
0.05 to 0.10 volts.
ON
Normal Operating Mode
c.
Battery A is lower than Battery B by
more than 0.10 volts
ON
Self-Protection Mode due to Overload Condition.
See below.
d.
Battery A is lower than Battery B by
more than 0.10 volts
OFF
The VANN-Guard is not functioning properly.
e.
Battery A is higher than Battery B
Abnormal condition. Suspect Battery B is defective or a 12 volt load
is connected to Battery B.
Overload Condition
An overload condition exists when the 12 volt loads exceed the VANN-Guard’s rated capacity. The
overload condition will not damage the VANN-Guard, but may cause damage to the batteries.
During the overload, the VANN-Guard’s output is limited by internal protection circuits to its Rated Output
Amps. The 12 volt amps exceeding the VANN-Guard’s output are drawn from Battery A which will begin
to draw the batteries out of balance. The VANN-Guard’s full Rated Output Amps are maintained as long
as Battery A and Battery B remain balanced within 0.10 volt. The internal protection circuits will reduce
the VANN-Guard’s output as the batteries become further out-of-balance. If Battery A voltage falls below
approximately 8 volts the VANN-Guard will shut itself OFF.
To correct the overload condition the 12 volt load must be reduced, or the VANN-Guard’s rated capacity
must be increased.
Trouble Shooting an Engine No-Start Situation
Situation:
A coach has dead batteries and won’t start while jump starting. The coach is equipped with a 24 volt
starting and charging system, a 12 volt electronic diesel engine control, a VANN-Guard, and a moderate
12 volt load which cannot be turned OFF. The coach sits for several days and the batteries run
completely dead. During jump-starting the engine cranks but does not start due to low voltage on the 12
volt supply. Electrical testing reveals there is no 12 volt output from the VANN-Guard while jump starting
even though the VANN-Guard separately tests OK.
Cause:
The 12 volt load which could not be turned OFF first ran both batteries down until the VANN-Guard shut
itself OFF due to low voltage. (The VANN-Guard will shut OFF if system voltage falls below 16 volts or if
voltage on either battery falls below 8 volts.) Then Battery A alone was drained to near zero volts.
As the bus is being jumped, 12 volt loads hold Battery A voltage too low for the VANN-Guard to turn ON
and Battery A is too weak to support the 12 volt electronic engine control.
Solution:
Turn OFF all 12 volt loads (turning the battery disconnect switch OFF may accomplish this). Connect the
jumper cables but do not crank the engine for two or three minutes. (Both batteries must rise above 8
volts.) The battery disconnect switch can then be turned ON and the bus should have adequate 12 volt
power to start.