Fuse charge wires or not?

[TeamHT]

I don't know why

[TeamHT]

Still not protecting anything. If you want to cover your base go ahead, but it's useless in my opinion.

I'm glad you can draw, but that doesn't address my point or the car manufacturers that don't fuse this same charge wire.

[ChevyBoy95]

I read threads like this and just shake my head . . .

how about stop shaking your head and give some explanation and clear some shit up.

[snafu]

refer to posts # 21 & 23

[79 cutty]

I read threads like this and just shake my head . . .

how about stop shaking your head and give some explanation and clear some shit up.

Seems like if he posted something useful (see top of page) you wouldn't read it anyways.

[SnowDrifter]

I'm glad you can draw, but that doesn't address my point or the car manufacturers that don't fuse this same charge wire.

I don't have an answer for that one. Every vehicle I've seen either has as outright fuse or a "fusible link" which is just a smaller gauge chunk of wire designed to melt/burn up quickly

And the correct answer is . . . (copied from our web site):

Most OEM charge leads have a fusible link on them. Its purpose is to protect on-board electronics in the event that the regulator fails and causes "voltage run-away." Although this is quite uncommon, fusing the charge lead included in any of our kits provides the same protection for your larger than stock alternator.

And YES, the fuse will in fact offer protection for this as voltage is that which causes current to flow.

Could you expand on this a bit more? I'm having trouble visualizing it in my head.

If you have an 85a alt, even if the regulator fails and it goes full field it still can't produce any more than 85a right? How will that 85a alt produce enough current to cause the fuse/link to blow and interrupt the flow of power?

[CortezDTV]

He is taking more so about voltage spikes, read the post after that

[snafu]

I see the confusion here. Yes, it is possible for an 85A alternator to produce more than 85A. Let's say that rating was provided at 14.4 Volts. If the regulator of the alternator were to fail and its output voltage increases so will its output current. Ohm's Law tells us so:

I = E / R

If R (resistance) is fixed, and it will be, then look what happens to I (current) as E (voltage) increases. Fuses are not designed to blow from excessive voltage. Fuses are designed to blow from excessive current.

Does that make sense?

[SnowDrifter]

That makes perfect sense.

So the higher the voltage, the higher the current, and the higher current blows the fuse, correct?


That brings up a different question: Does that mean an alt charging at 18v (for example) has the capability of putting out more current than an alt charging at 14v?

[snafu]

Correct and YES it does. However, let's say that a manufacturer designed an alternator to make 200 Amps at 14.4 Volts. And then you go sneaking around and up the output voltage to 18 Volts and now the alternator can put out 220 Amps. That may not be a good thing for the longevity of the alternator, as the internal components have a safe operating zone. Consider the following:

200 Amps x 14.4 Volts = 2,880 Watts

220 Amps x 18 Volts = 3,960 Watts (a 38% increase)

Not only would the internal parts have to tolerate this, the alternator itself would have to manage the additional heat - a byproduct of this extra power. Quality alternators are ALWAYS more expensive than crappy alternators because they have a larger safe operating zone for the internal parts. So, even though a pair of 200A alternators may make 200 Amps each, they most certainly may not be created equally. And that is exactly why one may be cheaper than the other - you absolutely do get what you pay for.

Incidentally, the exact same thing is true when operating an amplifier at any impedance below the manufacturer's specifications. As a result, most amplifiers are engineered to limit the maximum power the power supply and output devices will pass to keep it from failing when a greedy enthusiast asks it to.