ANL Fuse to Starter

[Down2TheC]

Just did an electrical upgrade. When it came time for implementation, I balked at using the ANL fuse.
ABYC wants it between the alternator and the batteries... fine. But our Westerbeke has one lead from the engine to the battery compartment. It serves both directions. Charging from the Alternator and providing juice to the starter. Not sure I want to run my starter through a fuse. I have a 100Amp ANL which was fine for the Alt. but I see no documentation on what the starter potentially draws.

Any opinions? It's a Westerbeke 50 with a 40A alternator. I figure the thing hasn't fried itself in 28 years, it should be okay without it.

[s/v Jedi]

No, I don't think they require you to put a fuse there if it is the standard alternator charging the starter battery (but they do when you charge house batteries). Then again, I am no expert on ABYC. In fact, I think they impose no requirements at all, just suggestions.

I have 3 alternators on my engine: the standard one which charges the starter batteries (and uses the same cable as for starting) which has no fuse, and two extra ones that charge the house batteries, which do have a fuse each. And the boat has the ABS approval so I guess it's okay.

On a down to logic level: the wiring between starter battery (both positive and negative) and engine should be rated to easily carry the starter current and also easily carry the alternator output current. The alternator isn't going to output twice as much suddenly, but if you change to a high output alternator you might need bigger wires (which is forgotten sometimes).

Your 40A alternator doesn't sound like it could fry the cable that also starts the engine so you should be just fine without the fuse.

cheers,
Nick.

[Down2TheC]

That's my logic. Starter will certainly have the potential to draw more from the batts than the alternator could provide, so the OEM W50 cable was rated for the starter. And while I haven't dug for the schematics, I'd bet there's some fusible links built into the engine package in case of short or excessive starter draw.

So... anyone in the market for an ANL fuse?

I should mention, it's on a combiner so I'm charging both batts (2 T105's and a basic starter batt) anytime voltage breaks 13V.

[CharlieJ]

The reasoning behind requiring an over current protection device at both ends of the alternator/battery conductor is to minimize the amount of unprotected conductor exposed to out of specification current should the alternator short to ground or the battery fails internally.

In your case, I would recommend installing the ANL fuse on the engine stringer close to the B+ stud for the starter and run the output from the alternator to the fuse and then to the B+ stud. At least that portion of the conductor is protected from the conditions noted above.

Hope this helps.
Charlie