Wiring Problem

The domestic battery bank doesn’t seem to be charging on KL when she is not connected to the shore power.  When I disconnected the shore-line and attempted to run the 240v AC from the Sterling inverter the alarm on the inverter sounded.  

Another thing Jan mentioned to me when was when we cruised to do the recent pump-out she could hear an audible alarm from within the boat.  Up to 800 RPM it is a constant sound.  From 800 to 1000 RPM there is a “chirping” sound.  The sound disappears above 1000 RPM.

The shore-power charges the two separate battery banks using CTEK chargers.

Note in the photo above that the top charger shows the starter battery fully charged after running the engine for the day whereas the bottom charger shows the domestic battery bank as being charged despite the engine running for the day.

The engine has two alternators.  One charges the starter battery and the other the domestic battery bank.  I could see the starter motor alternator was charging the starter battery.

My initial thought was the second alternator wasn’t charging the domestic battery bank.  Perhaps the alternator was faulty or a battery was defective.  The alternator belt might also be slipping.

However the domestic battery bank had been fully charged by the shore-power and yet the inverter alarm sounded indicating the domestic battery bank was flat.

It seems to me there is a problem with the configuration of the wiring circuit.  Peter agreed, and mentioned he recently had the domestic battery bank replaced as part of some major work.  I contacted the company who had completed the work and they sent out a serviceman to check the work.  He “jiggled” the isolation switch to the domestic battery bank and the alarm stopped.  He also measured the voltage at the alternator and advised it was fluctuating outside normal tolerances.  He recommended replacing both the isolation switch and the alternator.

Peter and I discussed this and agreed there appeared to be more to the matter than replacing the expensive alternator.  Working on the principle of “Look for the simple thing first!”  Peter decided to purchase a replacement isolating switch.

Today the repairman from “Snap-On” came to fix the fault whilst I employed my management & supervisory skills.

This is the new isolating switch.  A cheaper option than buying an new alternator.

OK…. by now you should have worked out the Snap-On repairman is Peter.  It’s quite a squeeze getting into the engine compartment (something I will have to get used to in the near future). 

Peter replaced the switch and “Voila”…… We still had the fault!   “Bugger!” Another theory shot full of holes.    The old switch received a squirt of CRC and Peter re-installed it.  Then I turned the inverter ON and OFF whilst Peter employed his superior sense of hearing catching the sound of an electric arc on a terminal.   Digging further back into the wiring loom Peter found a corroded and loose connection in the wiring between the isolation switch and the inverter.  He cleaned and re-tightened the connection before coating it with petroleum jelly.

Now the inverter works correctly.  No requirement for a new isolating switch or alternator.  Just goes to prove…….. “Look for the simple things first!”