Battery post fuse

[loun]

As an extra safety measure I would like to add a fuse to the battery cable that runs between the battery + and the starter. The cable is 10' long 2/0, want to size the fuse to handle the current from the starter (7.4 mpi merc). The chart indicates this wire can handle up to 400 amps. Would a 100 amp fuse handle the starter current?

 

[Scott Danforth]

Your starter pulls about 400 amps when it first hits, the drops to about 200 amps for cranking. There isn't an installation anywhere where there is a fuse on the starter lead. Bad idea, because if the fuse blows, after the motor starts, the alternator feedback goes to zero, alternator goes to full output and eats itself in a big blue glow

 

[bruceb58]

Yep, bad idea.

 

[wrench 3]

Your starter pulls about 400 amps when it first hits, the drops to about 200 amps for cranking. There isn't an installation anywhere where there is a fuse on the starter lead. Bad idea, because if the fuse blows, after the motor starts, the alternator feedback goes to zero, alternator goes to full output and eats itself in a big blue glow

Most starters don't go past 300 on start up. But I love your alternator scenario. It created an amazing mental picture.

 

[Bt Doctur]

First a bit of orange, the a blueish hue ,then lots of smoke and a burning insulaltion smell, not to mention spiking everrything that was turned on.

 

[thumpar]

I wouldn't recommend it but if you do it go with a circuit breaker and possibly 2 parallel so if one blows you don't blow anything up.

 

[GA_Boater]

Parallel fuses or circuit breakers never work. All it does is delay the 2nd blown fuse or popped circuit breaker. THEN the alternator goes all Chernobyl on ya.

 

[thumpar]

That is why I wouldn't recommend it in the first place but at least you have some amount of a small safety.

 

[bruceb58]

You never put fuses/breakers in parallel. What's the point?

 

[thumpar]

You never put fuses/breakers in parallel. What's the point?

Large amplifiers run them that way from the factory. Most of the time a fuse or circuit breaker will not blow unless there is a major problem. It would blow or trip both in that case. If it was an over amp (like starter pulling too much) it would keep them from blowing since the breakers are usually built for the amps, especially at the point of turning the key. 2 in parallel would only trip both if there was a short otherwise the other could keep the thing going to get to the dock.

I still don't recommend it though.

 

[bruceb58]

I am an EE and never heard of anyone doing that on purpose.

 

[Scott Danforth]

I worked for a large engine manufacturer and it is specifically recommended to NOT fuse the battery cable Heck, we used 125 amp fuses on the grid heaters alone.

 

[loun]

Glad I asked before I did it. Thanks for the information.

 

[thumpar]

I am an EE and never heard of anyone doing that on purpose.

Kenwood even has one with 3 fuses in parallel.

 

[StarTed]

Have you ever heard 400 amp fuses blow? You'd think there was an explosion. I've seen lots of 600 amp fuses used on 3 phase 480 volt services. Never saw parallel fuses.

If you want some kind of quick disconnect device, install a battery selector switch or something like that. That'd be a quick way to disconnect an extremely high load on a battery much quicker than loosening the terminal lug.

 

[bruceb58]

Kenwood even has one with 3 fuses in parallel.

Are they feeding the same circuit or 3 different circuits? I think you will find they are indeed not in parallel. Likely a 5 channel amp. Each 2 channels gets a fuse and the one channel that goes to a sub gets a fuse.

 

[thumpar]

Are they feeding the same circuit or 3 different circuits? I think you will find they are indeed not in parallel. Likely a 5 channel amp. Each 2 channels gets a fuse and the one channel that goes to a sub gets a fuse.

Possibly but I have seen 2 on a 2 channel amp. I doubt they would separate them especially on a cheap amp.

 

[GA_Boater]

How many consumer amplifiers draw or surge 300-400 amps. A stereo amp is not a starter.