Question for the electics experts..

[genphreak]

I blew my 80A fusible link, or rather it fatigued/broke- (ie no sign of melting.), all the classic symptoms- first I knew the wipers stopped, stereo died and OBC. Windows, courtesy lights and sunroof all dead...

Am having a bit of trouble finding another... perhaps I should bring myself to go to the dealer but I do happen to have a massive power block here so was wondering if it would be suitable:

It is the kind typically used to fuse multiple power amplifiers in bling stereo installs. It takes large glass fuses, available here in up to 60A each- and I'd like to install it to power some additonal 'accessories' anyway. It looks very like this;

http://www.skycraftsurplus.com/ProductImages/sk2002.jpg

As it connects straight into the car's existing battery cabling it makes for a clean and reliable setup... **except** the only problem is the big glass fuses are only availble in up to 60 Amps- not the 80Amps I need to replace one of my fusible links. Which begs the question...

Can I split the car's 80A cable to two and wire it to 2 seperate 40A fuses in this block. Thus they would be running in parallel. Would this equal the old 80A fusible link?

My intuition tells me that the current will use the path of least resistance (even within this small space) and burn out the first and then the second within the space of milliseconds once the load goes above 40A.

However I don't know if the spacing is sufficient for this to occur. As this thing takes 4 fuses it is ideal it be OK to do. I only need to use 1 fuse for the power amp and (potentially) 2 for the 80A cable. Then I can set about replacing the car's 50A link too and have the whoe car (except the starter motor fused under the back seat in one place. In the words of the immortal Yoda; "Nice, mmm yes this would be!"

Many thanks for your opinions, in advance... :) Nick

[Karl]

Seems to me that two 40A fuses should work OK. I'll see if the electrical wizards at the office can lend some insight.

[genphreak]

Seems to me that two 40A fuses should work OK. I'll see if the electrical wizards at the office can lend some insight.Thanks Karl, I have installed this thing and really don't want to have to fabriate an 80A fuse if 2 40A ones would do... :) Nick

[Claude]

I would think that your intuition is right.

Effectively you may look at those 2 parallel fuses as 2 resistors (very small one but with a certain resistance... very small fraction of 1 ohm) and as you mentioned the total load current will split on those 2 fuses, equally if it happend that those 2 fuses have exactly the same resistance (which is almost impossible), but if one is a bit more resistive than the other it will drain more current and when the require total current will raise near the 80 amps max one fuse will blow before the other and the second one will also blow immediatly not being able to take more than 40 amps .

Consider also that if those 2 parallel fuses are not perfectly balance (have not exactly the same internal resistance) the one that will have to support more current may a certain moment start to heat, this will increase the internal resistance difference between the 2 fuses... and this grather resistance inbalance with just accelerate the reach of the blow point of the first fuse with the same end result: not well protected.

That's my tought. Let us know what you will experience if you make a trial anyway.