What kind of fuses should I use?.??

MrNorm · Post by **MrNorm** » Wed Aug 31, 05 12:22 pm

With my battery in the trunk I'll be needing to fuse a couple of high current circuits, namely the alternator feed to battery, and the power line from the battery (NOT the starter cable - that's a separate cable). Both these are 8 gauge wire (8mm2) and the 'factory' type method that some people still recommend are fusible links - i.e. a short piece of wire 4 gauges smaller that will burn out with continual overcurrent (just before the harness itself would be damaged). Supposed advantage over a fuse is that it will carry an overcurrent for a little bit before blowing - i.e. won't blow like a fuse on a momentary surge. However, I don't know whether it's worth using these (or if they are available in the UK), or if I should just use a fuse, or a circuit breaker. There seem to be a bewildering array of potentially suitable types - strip fuses, maxi blade, cartridge type etc, I've no idea why you'd use one over the other.

So, you electrical wizards?
1) Is it worth using a fusible link, and if so where can you get them over here?
2) If a fuse, what is the best type, and what rating would I need for the main power cables (note, not starter motor current)

Holly · Post by **Holly** » Wed Aug 31, 05 12:40 pm

I'd go for a circuit breaker, simply because that could then be used to disable the car or easily disconnect the battery for welding ...

MrNorm · Post by **MrNorm** » Wed Aug 31, 05 6:32 pm

If I ever have to do any more welding on this car there will be trouble

...

.

Actually my master disconnect will take care of that function, but good suggestion!
I spoke to someone at work today who reckoned that the reason they used fusible links in the past was that the voltage regulation was not as stable as modern cars, therefore you were more likely to get spikes which could blow a fuse (but not a fusible link). So he reckoned a circuit breaker was the best in my application in case it did trip out (if I can't get fusible links)
Mind you, mopar had gone to electronic regulators by then, so not sure if that was an issue, but sounds like a circuit breaker might be the way to go???

Any other views on the above two questions??
thanks,

Blue · Post by **Blue** » Wed Aug 31, 05 6:59 pm

I use maxi blade fuses for anything over 30amps. My reasons for using them are the holders and any mounting hardware is easily and cheaply available, you can carry spares ( a fusible link might leave you stranded or at least be a pain to fix) and millions of modern cars have them and thier wiring designers are a bit cleverer than me! You could use circuit breakers if you want but it seems like an unnecessary expense.

Holly · Post by **Holly** » Wed Aug 31, 05 7:01 pm

BTW the '80s cars all use fusible links too, would have throught the regulators were fine at that point, but maybe they just got stuck in their ways or something (?)

Anonymous · Post by **Anonymous** » Wed Aug 31, 05 7:47 pm

Umm, I welded a dipstick to an airfilter housing, cos it touched the posi terminal during oil check - what a dipstick!!

MrNorm · Post by **MrNorm** » Wed Aug 31, 05 7:56 pm

Thanks so far, how about the rating???

And anyone know why all the different types of high current fuses (maxi, cartridge, strip, etc)??

Holly · Post by **Holly** » Wed Aug 31, 05 8:55 pm

I roasted a battery completely (ie. it worked fine before, didn't hold any charge after) with welding. Maybe I was just unlucky though!

I think disabling the vehicle is a handy function to have too

MrNorm · Post by **MrNorm** » Fri Sep 02, 05 8:19 pm

Thanks everyone for responses up until now, all read and useful.
I did a fair bit of web research and I concluded that fusbile links were chiefly used by the OEM's because they were cheap, plus I'm not sure high capacity fuses were available then.
Modern high capacity automotive fuses (e.g. Maxi, Midi, Mega) are 'slow blow' types, therefore suitable for replacing fusible links even if you do get spikes in the system.
Also, Blue was kind enough to talk to one of the experts at his work, who recommended the Mega fuses over Maxi blade since they have large posts and are bolted down.
You get less resistance from a bolted down connection from the 'slot in' blade type, so sounds like a good way to go.
Taking a look, I can only find Mega fuses above 100A ratings, so I might have to go with a Midi fuse - exactly the same principle as Megas but with smaller posts (5mm ilo 8mm) and available in smaller ratings.
Circuit breaker is still an option, I'll price them up since the price gap is not as great once you start using midi/mega fuses.
As far as rating is concerned - I think the stock Mopar alternator is 50 amp MAX (some are less), I'm wiring up with 60 amp cable, so I guess a 60 amp fuse should do the job fine?

Kev · Post by **Kev** » Fri Sep 02, 05 8:36 pm

I reckon a 60amp will be fine taking into account diversity. Haven't you got an RS account at work?

MrNorm · Post by **MrNorm** » Sat Sep 03, 05 6:58 pm

Diversity??? What's valuing others differences got to do wiv me fuse

Kev, I don't think they let me anywhere near the RS account...I could bring the company down