Fuse For Battery Cable Protection

[ggray]

Do any of you have a fuse on the battery cable going to the motor? AFAIK this was not done in the past, but I've read that it is now being recommended.

There was a recent thread of a battery post melting, and a properly sized fuse would have prevented that. Of course, a fuse doesn't correct an existing problem, but it would prevent further damage, even a fire.

So I'm curious what others are doing.

 

[theoldwizard1]

Re: Fuse For Battery Cable Protection

I have never seen it, but the do make "mega-fuses" that are 100A and up !

 

[Bondo]

Re: Fuse For Battery Cable Protection

Do any of you have a fuse on the battery cable going to the motor? AFAIK this was not done in the past, but I've read that it is now being recommended.

There was a recent thread of a battery post melting, and a properly sized fuse would have prevented that. Of course, a fuse doesn't correct an existing problem, but it would prevent further damage, even a fire.

So I'm curious what others are doing.

Ayuh,.... A fuse won't fix Corroded wirin' connections, 'n Won't stop that happened,...
It wasn't a Short,....

The newer I/Os have a 90a, Lawyer's fuse mounted to the starter,...

 

[MH Hawker]

Re: Fuse For Battery Cable Protection

I have seen and used fuses up to 500 amps at 69,000 volts. How ever at 12 volts 200 is the biggest i have seen. Those are for whats known as a catastrophic failure in battery chargers.

In a boat application I have never seen a fuse in the main power lead going to the solenoid and starter you have to consider the high cranking amps. I am sure if you really want to dig into it you can find whats known as a slow blow fuse that may be able to stand the cranking amps, but i tend to believe it wont give you any protection.

 

[ggray]

Re: Fuse For Battery Cable Protection

Thanks for thr responses.

I think I'll install a fuse and see what happens!

 

[UncleWillie]

Re: Fuse For Battery Cable Protection

...I think I'll install a fuse and see what happens!

The problem is that the wire gauge that is used in the starter circuits of Boats and Autos is under-rated for the application.
When you turn the key, the starter motor may draw in excess of 1000 amp for a few 10's of milliseconds.
Within a quarter second, the current will stabilize in the 200 amp range.
The heavy #2 AWG Battery Cable is rated for 130 amps if you are willing to let it heat up to 90?C (194?F). Seriously HOT! (#4AWG, 95A)

If you install a Fuse smaller than 130A it will Blow every time you try to start.
If you install a Fuse larger than 200A, the wire will melt before the Fuse will Blow.
It is a No-Win Situation.

The engine will typically be started in well less that 30 seconds.
The wire will get noticeably warm, but will survive the intermittent event.
The starter motor is also only rated for intermittent operation.
That is why you are instructed not to crank for more than 30 seconds in any two minute period.
If you do not let it cool between attempt, You WILL smoke it.

Autos have be starting just fine for over 100 years without any fuses in the starter circuits.
With just minimal maintenance, the odds are that you will not burn up any Boat or Auto in your lifetime.

 

[tazrig]

Re: Fuse For Battery Cable Protection

+1^^^ no need for a fuse there. You'll just keep blowing it.

 

[dingbat]

Re: Fuse For Battery Cable Protection

Lawyer's fuse....I like that. Solutions to non-existent problems

 

[agallant80]

Re: Fuse For Battery Cable Protection

Thanks for thr responses.

I think I'll install a fuse and see what happens!

I would leave it alone. You are kinda reinventing the wheel here and could introduce additional issues. If melting battery posts were a real problem or even a potential problem than there would be a "lawyer fuse" on the cable already. It was a fluke and who really knows what really happened in that case, all we have to go on is what the OP said about his post melting.

 

[alldodge]

Re: Fuse For Battery Cable Protection

Do any of you have a fuse on the battery cable going to the motor? AFAIK this was not done in the past, but I've read that it is now being recommended.

There was a recent thread of a battery post melting, and a properly sized fuse would have prevented that. Of course, a fuse doesn't correct an existing problem, but it would prevent further damage, even a fire.

So I'm curious what others are doing.

Do you think you may have the alternator fuse (90 AMP) which is mount on the starter mixed up with the discussion of one on the battery cable?

 

[Fed]

Re: Fuse For Battery Cable Protection

When a fuse blows from fatigue after many heating cycles and your boat washes onto the rocks do they re-name the lawyer fuse to defendant fuse?

 

[Grandad]

Re: Fuse For Battery Cable Protection

In my experience, every time you have another termination or contact point, you introduce another point that may fail from vibration, aging or corrosion. Depending upon where you use your boat, the inability to start the engine because of a failed connection point could invite disaster. I wouldn't add the fuse. - Grandad

 

[gm280]

Re: Fuse For Battery Cable Protection

My 1 1/2 cents on this one.

I am on that proverbially fence on this situation. The FACT that the OP had not one but two batteries where the terminal posts melted out of them, is a head scratcher to me. As I understand such an event, it would seem like there was some very serious current flowing to produce such high heat. And from my elementary Electrical experiences, that points to a very severe low resistance somewhere. The lower the resistance the higher the current draw. So I say yes there is something shorting out to cause such a catastrophic melting for TWO battery terminals. Corrosion will cause resistances but not so low as to increase current flow. On the contrary, it induces resistance to current flow and the corroded section would be the heat source then as well, not the power source terminal(s) unless the battery cables were the corroded source. But if the battery cable ends were such a source of corrosion, that would be quite obvious to most anybody to see and cause the problem. So I would certainly be checking the entire circuit from the battery through the starter solenoid and of course the starter itself for any problems before frying another battery... I'd even take them off and have them tested at an auto parts store just to rule them out!

 

[MH Hawker]

Re: Fuse For Battery Cable Protection

I am also watching that thread I am sure the starter is grounded. Thats the only thing i know of that will cause it.

 

[Bondo]

Re: Fuse For Battery Cable Protection

My 1 1/2 cents on this one.

I am on that proverbially fence on this situation. The FACT that the OP had not one but two batteries where the terminal posts melted out of them, is a head scratcher to me. As I understand such an event, it would seem like there was some very serious current flowing to produce such high heat. And from my elementary Electrical experiences, that points to a very severe low resistance somewhere. The lower the resistance the higher the current draw. So I say yes there is something shorting out to cause such a catastrophic melting for TWO battery terminals. Corrosion will cause resistances but not so low as to increase current flow. On the contrary, it induces resistance to current flow and the corroded section would be the heat source then as well, not the power source terminal(s) unless the battery cables were the corroded source. But if the battery cable ends were such a source of corrosion, that would be quite obvious to most anybody to see and cause the problem. So I would certainly be checking the entire circuit from the battery through the starter solenoid and of course the starter itself for any problems before frying another battery... I'd even take them off and have them tested at an auto parts store just to rule them out!

Ayuh,.... In that thread, Corrosion, At the Battery Post, is the Only explanation,....

A Dead Short anywhere else in the circuit, would cause heat, There,...
Not at the battery post, if in fact the battery post was Sanded Clean, along with the connector,...

Most folks don't understand that a battery connection, Ain't clean enough, unless it's Shiny Metal Clean,...
Even a Brand New battery, right off the shelf has a coatin' of corrosion,...
That's why they look like a dull lead color, 'n not Shiny Metal,...

 

[JustJason]

Re: Fuse For Battery Cable Protection

The newer I/Os have a 90a, Lawyer's fuse mounted to the starter,...

Just so there is no confusion. That fuse there is not a main battery cable fuse. That is there to help protect the engines harness and alternator from burning up. But not to protect a battery cable.

 

[bruceb58]

Re: Fuse For Battery Cable Protection

Normally corrosion on a battery post would cause less current. The exception is with a motor like a starter motor. Because of the resistance, the motor doesn't have enough voltage so it stalls or partially stalls therefor demanding more current than it normally would. That is what causes the battery terminals to get very hot.

 

[Outsider]

Re: Fuse For Battery Cable Protection

As I understand such an event, it would seem like there was some very serious current flowing to produce such high heat.

I once melted a post after moving batteries around and replacing some cables. WTF, says I, couldn't find anything wrong! Until, that is, I figured out I had connected the batteries in series. Blew the lawyer's fuse, too, thankfully it preformed as advertised. Melting terminals means there's something seriously wrong, and a fuse ain't gonna fix it ... :facepalm:

 

[UncleWillie]

Re: Fuse For Battery Cable Protection

As I understand such an event, it would seem like there was some very serious current flowing to produce such high heat...

And there is some very serious current flowing!
A motor is NOT like a light bulb, The current it will draw is determined by its Inductive Reactance which changes dramatically with the RPM.

A slightly simplified explanation...
A starter motor may have an inherent Resistance in the neighborhood of 0.01 (1/100) ohms.
If it is NOT turning it will draw over 1000 amps. At normal speed it will draw ~200 amps.
If the bad battery post also has 0.01 ohms, and Yes! That is almost nothing, but it is a Fatal almost nothing;
The total circuit resistance is 0.02 ohms, and at 12 volts produces 600 amps and 7200 Watts!
BUT! the 0.01 ohms at the battery terminal is going to drop 6 volts at 600 amps.
The other 6 volts is all that Starter Motor gets, so it stalls, and as not turning, just remains a 0.01 ohm resistor.
Both that starter and the Battery terminal are going to share that 7200 watts equally.
At 3600 Watts, the starter being physically large is still going to get seriously hot in short order.
The little lead battery post doesn't do as well. The 3600 watts will have it melting in a few seconds!
A second later, the battery cable falls off and the disaster ends.

On second thought the Battery Cable IS Fused! The Battery Post is the Fuse!

Battery Cables and Connectors require less than 0.001 (1/1000) ohms for proper operation.
You can not measure resistances that small with common test equipment.
Proper, secure, and spotlessly clean connections are mandatory.

 

[Auger01]

Re: Fuse For Battery Cable Protection

Works great, lasts long time:



Motor is an F90 Yamaha. The blue strap is the battery hold down strap. The small fuse holder to the right of the 200 amp breaker is for the onboard battery charger.