Bosch Alternator Causing Possible Current Spikes!!!!!

[Hateblownfets]

We have a Bosch 200 Amp Alternator on a 2.4 Litre Petrol Toyota Hi Ace. The system keeps blowing power supply Mosfets in amplifiers, we had the system running today with2 x Orion Cobalt 3200d amplifiers strapped together. Now when we started up the vehicle today we revved the engine and all of a sudden, crack, it blew the 5 25A Fuses. With this Bosch 200 amp alternator the warning light circuit has always blinked 4 times when we start it up. It's like it takes 4 pulses to excite the Alternator into charging when first started. The problem is everytime its starts to charge I have measure the amps with my clamp meter and today it spiked up to 135 amps for a second and back to what its sits at charging voltage at 14.2 My question is could this spike be enough to blow mosfets? Voltage is never higher than 14.3 even when it spikes....I'm sick of this setup blowing mosfets, we hadn't even used the subs on this amp, and why would it only blow 1 amp and not the other? it was the amplifier setup as the slave that blew. I have a phoenix gold 4 channel and that is hooked up to same battery and it has never blown mosfets....I need help please thankyou :-)

[whazoo84]

We have a Bosch 200 Amp Alternator on a 2.4 Litre Petrol Toyota Hi Ace. The system keeps blowing power supply Mosfets in amplifiers, we had the system running today with2 x Orion Cobalt 3200d amplifiers strapped together. Now when we started up the vehicle today we revved the engine and all of a sudden, crack, it blew the 5 25A Fuses. With this Bosch 200 amp alternator the warning light circuit has always blinked 4 times when we start it up. It's like it takes 4 pulses to excite the Alternator into charging when first started. The problem is everytime its starts to charge I have measure the amps with my clamp meter and today it spiked up to 135 amps for a second and back to what its sits at charging voltage at 14.2 My question is could this spike be enough to blow mosfets? Voltage is never higher than 14.3 even when it spikes....I'm sick of this setup blowing mosfets, we hadn't even used the subs on this amp, and why would it only blow 1 amp and not the other? it was the amplifier setup as the slave that blew. I have a phoenix gold 4 channel and that is hooked up to same battery and it has never blown mosfets....I need help please thankyou :-)

The short answer is no, the long answer is yes. Let's dive right into this!

Okay so you guys know how after starting, your alternator will spike to charge the battery, for a short second. Even my self exciting one does that, they all do. However, 135A is a large spike, abnormal. I'd say between 50-60A would be normal, as most stock alternators could only do that at idle to revive battery voltage.

Now, a spike higher than 14.3 for the smallest bit of a second would just be absorbed by the amplifiers internal capacitors, however if it lasts for even a second, now the internal caps of the amplifier are charged to the spike's voltage. The problem is, we don't know the voltages.

Another thing to note is that Alternators get their name from them generating Alternating Current, and then rectifying it to DC. A DC generator on a car would be lossy and inefficient. The battery basically acts like a capacitor for this, even though the fluctuations coming from the AC-DC transformation are minimal. However, I have my suspicions that the alternator may or may not be at fault, and here's why. The alternator might do this: release an AC current through a shorted diode, however once the diode gets hot from the current spike it will go back to normal. If this is happening, it's destroying the electrical system in the car, slowly but surely.

Now guess what, I'm about to throw a wrench in the gears because here's another huge possibility. A short in the head unit's output.

What? How could this effect anything? A short in the output will flow a DC current through it, not an AC. So basically, you're shoving a DC current through the RCAs to the amplifier. If this happens, the amplifier is also passing the DC current and frying the shit out of itself. This could cause the spike upon startup as well, a DC current flowing temporarily overloading the alternator might do this. The warning light might be on because until the alternator kicks in, the voltage on the batteries is very low due to a high draw. Now this could explain the peaking amperage because as I said, it's trying to make up for lost voltage. Even though this is unlikely, we're dealing with a strange situation so I have no idea what is going on. Unless I'm at the car myself, I can't do anything. I can't test it or help you, if I could I would.

Hope some of this info helps.