Hi all,
I have found a fault in the original wiring of the electrical system
of late MD6A installations, which have a combination of the Dynastart
DC generator, and an AC alternator. This is probably already known,
but I thought that my discoveries could be interesting to the people
out there who have problems of getting the alternator to charge
correctly.
The fault is how the alternator indicator lamp is connected to the
ignition switch. Originally it is wired directly to the same post as
the Dynastart indicator lamp which means that when the ignition key
is switched on, the starting battery is supplying 12V to both
indicator lamps. This is wrong. The purpose of the lamp is to have a
connection between the battery, which is being charged, and the so
called excitation of the alternator. If this is connected to another
battery than the one being charged, it means that when that battery
is fully charged the alternator lowers its output in order to not
overcharge. The indicator lamp will still go out since there is very
little current flowing through it. With the very easily started
engine that I have this means that the starting battery is almost
directly fully charged after start and the the alternator voltage
regulator senses this through the indicator lamp, and stops charging
the consumption battery. It was very puzzling for me why the
alternator output voltage was lower at higher rpm's, before I
understood this. Fortunately, the problem has a simple solution:
Connect a relay between the consumption battery and the alternator
indicator lamp. The relay should be controlled from the ignition
switch. This way the correct battery voltage is sensed, and the
charging now works perfectly with 14.2 Volts almost independenly of
the load I put on the battery.
So if you think that your alternator is faulty, this may be the
problem. Otherwise I think that the system with two completly
independent sources of power is excellent.
Carl
V-2290
I have found a fault in the original wiring of the electrical system
of late MD6A installations, which have a combination of the Dynastart
DC generator, and an AC alternator. This is probably already known,
but I thought that my discoveries could be interesting to the people
out there who have problems of getting the alternator to charge
correctly.
The fault is how the alternator indicator lamp is connected to the
ignition switch. Originally it is wired directly to the same post as
the Dynastart indicator lamp which means that when the ignition key
is switched on, the starting battery is supplying 12V to both
indicator lamps. This is wrong. The purpose of the lamp is to have a
connection between the battery, which is being charged, and the so
called excitation of the alternator. If this is connected to another
battery than the one being charged, it means that when that battery
is fully charged the alternator lowers its output in order to not
overcharge. The indicator lamp will still go out since there is very
little current flowing through it. With the very easily started
engine that I have this means that the starting battery is almost
directly fully charged after start and the the alternator voltage
regulator senses this through the indicator lamp, and stops charging
the consumption battery. It was very puzzling for me why the
alternator output voltage was lower at higher rpm's, before I
understood this. Fortunately, the problem has a simple solution:
Connect a relay between the consumption battery and the alternator
indicator lamp. The relay should be controlled from the ignition
switch. This way the correct battery voltage is sensed, and the
charging now works perfectly with 14.2 Volts almost independenly of
the load I put on the battery.
So if you think that your alternator is faulty, this may be the
problem. Otherwise I think that the system with two completly
independent sources of power is excellent.
Carl
V-2290