2011 C26 Electrics - Alternator Diodes

[Diatom]

Trying to unravel the mysteries of an older Cutwater, I collected the following admonitions about alternator diodes:
1. "Never switch on the inverter while engine running" for fear of damaging diodes.
2. "Never operate the house, nor engine, switches while engine running" for fear of damaging diodes.
3. "Never operate an alternator without a load" for fear of damaging diodes.
4. "You can leave your inverter on 24/7 if you have shore power".
5. "Turn your inverter off if moored without shore power - it drains the batteries even without a load".
6. "The red rotary switch with an "M" on it in the starboard cockpit lazarette is the inverter switch".

Are these consistent with prevailing wisdom?
Are there other ways for a newbie to fry them?
How would diode failure be manifested? (Presumably battery drain... some manner of alarm/indicator?)

/Diatom

 

[BB marine]

I don't think #1#4 are correct

#2 could be correct if the house battery is servicing the engine electrical circuits. I don't think a factory install does this. #2 is correct when talking about the engine battery and engine electrical circuits.

#3 is correct when calling the engine battery the load for the alternator

#5 is true the inverter does use a small amount of battery amps/watts while on stand by.

#6 I'm not sure of the label for the inverter battery switch. I would follow the battery cable coming off the switch (load side) to the termination or component it is feeding.

Two most common owner operator faults that cause the diode trio or voltage regulator to fail are (1) turning the load off ( battery) while the engine is running, (2)Connecting the engine battery cables to the battery with reverse polarity.

There are several operating reasons for an alternator diode trio failure but not in line with your questions.

 

[Martin610]

Brian is right, 1-4 are not correct.

One other thing to be aware of if you have a separate inverter and charger. Turn charger off if using the inverter. This is the scenario you might have at anchor. Many people leave the charger on while connected to shore power. If you leave the charger on and then turn on the inverter you can create a 'loop' and damage the inverter. The internal fuses may not blow fast enough to save the unit. Many inverters have an alarm but it might not be heard over wind, waves, kids, etc.

An inverter/charger combo unit should automatically turn off the charger when the inverter is energized.

 

[Chimo]

Just for the record, I ALWAYS, start the engine before switching on the inverter if at anchor. Never had a problem.

 

[Diatom]

Thanks for your comments folks - I'm a bit taken aback by the lack of documentation on this thing, trying to assemble my own drop-dead manual (and avoid idiot-errors in the process).

/Diatom