Alternator to Battery Wire

[Robrover]

I noticed that the thick wire running from my alternator to the battery positive is not fused at all. I understand that some car manufacturers purposefully did not put a fuse in this wire connection. Others, like Ford and Honda, use fusible links located near the battery. As the wire is connected to the positive terminal it looks sensible to me to include a high amp fuse or even a circuit breaker in case of a crash that could damage this wire and possibly start a fire.

So my question is why do some makes have fuse protection on the alternator to battery wire and some do not? And do you think it is advisable or not to install one (fusible link or circuit breaker)?

 

[stevieturbo]

Rarely is this fused....at least certainly on older cars.

Perhaps with more modern very output alternators these days, and of course cars with a far higher demand for power from the alternator it just makes some sense to fuse it.

Plus with modern stuff...better fuses are available.

Lets face it, what 100A fuse options where there for vehicles 20 years ago ?

So it's a balance between what the alternator may need to send out and whether it's practical to get a fuse to cope with that and carry sustained load without it melting and going on fire.

Protection is always a good thing, doesnt mean it is always practical.

And perhaps with older alternators...maybe they just went bang as overcurrent protection ? Almost like a fuse in itself ?

[SimpleSimon]

Everything as fusible links in the alt feed nowadays even on the starter cable on some personally I would have one in place if I was wiring from scratch just dont use a blade/strip style as the fusible link they corrode and get brittle with age use a proper Midi fuse link, I cant comment on every brand but when I was a Honda tech back in the day they all had them fitted and every one that had failed was due to storage companies/recovery companies or daft owners jump starting with the battery polarity crossed not one of those vehicles suffered alternator damage (usually do blow the internal diodes) or any other damage due to the above but each and every one blew the fusible link if your going to fit one I would go for something like this http://www.12voltplanet.co.uk/midi-stri ... older.html make sure you spec the fuse for the alt you intend to use, and I agree with Stevie back in the day nothing used fuse links between alt and battery

[DaveEFI]

When you go up to the sorts of currents alternators use, you're often into screw terminal connection territory, rather than push on. And no matter where you put a 'fuse' there is always something before it with no protection, like the battery itself, or the wiring to the fuse.

[wesbrooks]

Just planning a loom for a 4x4 at the moment which is proving to be an education!

While many looms don't fuse the starter or alternator I see little reason why you shouldn't consider it now. You can also get fused battery terminals that offer protection at up to 500A. That's excessive for the 1.8kW starter on my RV8. I'll be considering a 200A fuse before the starter and chunkier fuses for winches.

One thing to consider though is what the battery is capable of delivering. If you've only got 500 cold cranking amps available it may struggle to pop a 500A fuse in a dead short. The amperage rating of fuses are the maximum continuous current they will support, rather than the rating that will cause an instant fuse failure.

I think my '95 Discovery that I used as a donor had a 200A alternator fuseable link, but no fusing for the starter, or main battery lead.

[richardpope50]

My 1997 TVR Griffiths had a 100 amp fuseable link so I simply carried that over to my kit car.