OK. All these ideas have really got my thinking going, and with it, my memory.
First, some facts in response to questions:
1. The
bilge pump wire from Batt 2 pos has its own fuse within 3 '' of the terminal.
2. My battery switch is a Blue Sea dual circuit combo switch, with the main line to the distribution panel at the output side of the batt 2 switch.
3. Starter cable comes off the batt switch.
4.
Current electrical layout not ideal in terms of minimal cable run. This 1972
Ericson has the
engine in mid-cabin, battery bank mid port side of engine, but battery switch, AC panel, DC panel all on starboard side at aft end of
galley. So two large battery
cables and a large starter cable make the trip through bulkheads, around corners, across the boat and back, maybe 25' round trip.
5. All circuits are appropriately breakered to load, and the only line without a fuse is the starter cable from battery switch, output 1, to starter.
6. At the moment I can't
recall where
alternator comes in.
7. The key to this puzzle may be that this is not a static layout, but a
work in progress that looks different every week.
Here's my logic, and my tentative answer:
1. From
Maine Sail, Bill, Stu Jackson, W3GAC and others: The answer has to involve
current flow through the large diameter
cables. Otherwise, there would be some evidence, somewhere, of heat destruction in a circuit, which I have not found yet.
2. The fact that both fuses are blown does not necessarily mean they both went at the same instant.
3. If nothing makes sense, find the human factor that caused the problem.
Additional points that I am only now thinking to give you:
4. This rewiring
project has been a part time effort for almost a year. During that whole time, the boat has not sailed, but I have run the engine periodically.
5. I've only had the new DC panel with its new battery switch in for about a week.
6. Prior to that, without proper DC
wiring, I decided I needed to run the engine for at least a short time to keep it lubricated, etc. My quick solution 2 weeks ago, was to take the loose end terminals of each of the two positive battery cables and the starter cable, bolt the three together, turn the ignition key, and push the starter. Engine fired right up.
7. I have the DC negative, AC ground, battery negative, all bolted to the engine block as a common ground. The
shore power fitting by the marina is 1 year old and probably working well.
My theory: The 100 A fuses are too small for a 190 CCA 20 HP
diesel engine. There has been at least this one time, maybe others I don't
recall, where battery 2 as well as battery 1 was part of a high current starter event.
Maybe the fuse link melted all the way through on batt 2, only most of the way through on batt 1 during one or more of these episodes. I would not have known that one fuse was out because I have no
monitor for that, and had no DC circuits operational yet (lights, blower, etc.) The second one then completed its death at some random moment, like while I was turning battery switch on and off while troubleshooting.
If any of this is true, then from all of you my steps going forward should be:
1. Get larger fuses for the starter circuit, maybe 250-300A at the batter terminal.
2. Run larger cables to match the larger fuses.
3. Do a very thorough check for a dead short somewhere, starting with the old large cables, particularly where they are hidden.
Have fun with my theories, and I appreciate all the great ideas!
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