Stetsom 7KD and fuse questions

[Mtxplod 0]

So i purchased a stetsom 7KD and I am curious what the external fuse rating is. i looked up the manual online but it only has info for the two ohm version. The one i purchased is the one ohm 12 volt version.

Also when i install this amp I will add another battery or two to what i have.I have noticed that a lot of setups have unfused connections on their terminals. As of now i have two batteries with two fuses 12 inches from each terminal. so if i install a third would i need another two fuses or would that only be necessary if they were a certain distance apart?

And of course when i do the install i will do another positive run and dual input terminals.

Thanks

Edited January 23, 2013 by Mtxplod

[Quentin Jarrell 671]

Google ohm's law.

[djjdnap 78]

Depending on your wire ur not gonna be able to pull the max amount of current anyway.

I think 25ft of 1/0 is like 400A.

But you would be fine with 300A IMO given eff.

I found tis to be pretty helpfull and funn if you want to deal with numbers...

Quote: I was talking to a friend about this and he provided me with the conversion from watts to amps and his opinion = "(Watts / 12) x 1.1 = actual DC amps.

Well, sort of. Power(Watts) = Voltage(V) x Current(amps). I assume the 1.1 factor is to account for 10% inefficiency. However that is power dissipation for the voltage drop across a given element or system while passing that amount of current.

Very poor wording on my part, but you can't exactly calculate an amplifier's power output from the amount of current it draws without more detailed information. You can make an estimate if you know the efficiency of the amp.

We can calculate the current through a 1ohm load dissipating 2000W. That's the square root of (power/resistance.) Which turns out to be 44.7 amps. Through the one ohm load.

The Crutchfield page listed says the amp is 75% efficient. We don't know under what conditions this 75% efficiency was measured. But that's all we have to work with, so the amp will have to draw 2667 Watts to deliver 2000 Watts to the speakers.

The output power is rated at 14.4VDC input. 2667 Watts drawn from a 14.4V supply would require (current = power/voltage) 185 amps. The extra 667 watts are dissipated by the amplifier as heat.

IF (that's a big "if") the amp would continue to increase power in a linear fashion with the current drawn from this point...

AND IF it were to need to draw 250 amps from the batteries,

AND IF the batteries/alternator could deliver it,

AND IF there were still 14.4V at the DC input on the amp,

AND IF it were still 75% efficient at this point,

AND IF it were driving a load of exactly one ohm,

AND IF we lived in a perfect world...

The power INTO the amp would be 250A x 14.4V = 3600W. 75% of that, or 2700W would be delivered to the speaker after the amp was done amplifying, and 900W would be heating up your trunk.

BUT, the fuse is for protection. The amp isn't necessarily fused at the amount of current needed for rated output at minimum load. We can only reasonably assume that it's specifed at a margin of safety:

1) above the current needed to provide 2kW output while driving the maximum 1ohm load, but

2) below the current needed to do serious damage to the amp.

I've seen amps almost melt before blowing a fuse.

Tim

[Mtxplod 0]

I was considering all of the "if" situations which is why I ask.I was hoping someone had some experience with this amp. But a 300A fuse huh? the maximum current draw on this amp is 480A and I plan on running it at a half ohm... so after rise it may see as low as 1.4ish

Thanks.

[bassahaulic 155]

How many inputs does the amp have? Also, how far away are your batteries from your amp?

[Mtxplod 0]

For now it has single inputs, but I plan on putting in some dual input terminals on them.

the closest battery to the amp will probably run 24-36 inches.

[Mtxplod 0]

Maybe i could give circuit breakers a try? or would that not be in my best interest?

[djjdnap 78]

I dont like circuit breakers.

But its your system and your car, so however you want to protect it is up to you.