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Old 05-24-2011, 12:00 PM   #1
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Fuse on starting battery

I put a fuse holder on my starting battery with a 200 amps fuse. The fuse blew right away. What size fuse would I need? 300 amps? Do you have a fuse on your starting battery?
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Old 05-24-2011, 01:39 PM   #2
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RE: Fuse on starting battery

Hobo's starting battery is fused with a 400amp, Class T fuse.
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Old 05-24-2011, 07:49 PM   #3
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RE: Fuse on starting battery

You should be able to find out the inrush current for the starter, and that will guide the selection of the right fuse. *Here's a source I use:

*

http://amplepower.com/products/fuses/index.html
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Old 05-25-2011, 03:41 AM   #4
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RE: Fuse on starting battery

I can understand a really heavy duty switch ,(see Practical Sailor) but why a fuse?

The most common failure is probably the starter bendex sticking , and the spinning starter throwing 100V or more into the vessels electrical system .

A switch will stop it , or a starter fire , but a fuse works on Amps , so probably wont mind a bit.
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Old 05-25-2011, 08:40 AM   #5
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RE: Fuse on starting battery

When we bought the Eagle already had a 500 amp fuse, which we blew the fist time we took the boat out as we changed the filter and got air in the lines, cranking the 671.* The engine ran long enough to get out of the marina and died.* Being a newbie did not know diesel do not like air in the fuel lines.* Luck would have it the wind blew us right into the Lake Union Police marina, which they of course got all excited.* However, they were nice enough to have their mechanic bleed the engine and find the fuse, so we would get off THEIR DOCK.*
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Old 05-25-2011, 09:01 AM   #6
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RE: Fuse on starting battery

Quote:
FF wrote:
The most common failure is probably the starter bendex sticking , and the spinning starter throwing 100V or more into the vessels electrical system .

*This happened to one of the boats (40 Viking)*on our dock last summer. One of the twin*Detroit 6-92 450s. The owner ran the boat about an hour + with the starter engaged. Did not know, couldn't hear the starter, but the exhaust sounded "funny". Did not*overload boat's electrical system except for burning up the starter.

*
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Old 05-25-2011, 09:25 AM   #7
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RE: Fuse on starting battery

Thanks. The more I think about it the more I don't see why I would put a fuse on the starter battery.
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Old 05-26-2011, 03:50 AM   #8
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RE: Fuse on starting battery

A second problem is many alternator outputs simply go to the starter terminal.

Its close , and the wiring is always ample to handle the alt output.

Should a fuse disconect an operating alternator its usually diode time.

Have the press and spare diodes aboard?


A good rotary switch and proper wiring solves this.

There is (on a good rotary switch) an alternator field power terminal.

It breaks the alt field before disconnecting the selected batt.

Connects the batt , then powers the alt , when selecting a batt.

GREAT INSURANCE , if your alt is hooked to the starter.

IF someone were to go to the trouble of rewiring to install a field disconnect switch , I would add a manual switch in the event of V reg failure, with the chance of over voltage charging, boiling battsets.
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Old 05-26-2011, 10:17 AM   #9
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RE: Fuse on starting battery

The reason you might is I beleive its ABYC standard.* We had an insurance audit that went through the Eagle from the*bow to the stern and had to bring the Eagle up to ABYC standard.*
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Old 05-26-2011, 08:02 PM   #10
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RE: Fuse on starting battery

ABYC 11.10.1.1* exceptions to overcurrent device requirements:

1.* Cranking motor conductors
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Old 05-26-2011, 09:12 PM   #11
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RE: Fuse on starting battery

We have a 500 amp fuse in our starting motor circuit. Just noticed it last week and wondered what it was for. Maybe the fuse is viewed as a safety switch so when someone lays a wrench across the terminals the fuse limits the time of extreme current. Could be fire safety. How hot would a battery cable get w over 500 amps going through it?
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Old 05-27-2011, 04:10 AM   #12
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RE: Fuse on starting battery

How hot would a battery cable get w over 500 amps going through it?


Depends on how thick the cable actually is.
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Old 05-27-2011, 06:42 AM   #13
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RE: Fuse on starting battery

Don't fuse the starting battery, disconnect switch yes, fuse no.
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