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can this be overloading my alternator?


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menaztricks 
Member - Posts: 28
Member spacespace
Joined: October 30, 2005
Posted: August 05, 2006 at 10:45 PM / IP Logged  
The alternator in a 99 cavalier just went bad on me, eventhough its about a year old. Since I changed it, I added an amp to the car, its a 700w bazooka. The alternator in the car is 105amps, would that amp need a stronger alt?
desolationangel 
Member - Posts: 6
Member spacespace
Joined: November 27, 2005
Location: United States
Posted: August 06, 2006 at 2:42 AM / IP Logged  
Couple things. 1.sorry about your alt that sucks. Hope it dosent put ya off the road for more than a day or so. 2. There is no reason your 105amp alt cant handle your 700w amp. Not sure what the wiring looks like inside the cavi but something is wrong. Check and try these items.
1. did you upgrade the "Big 3"?
2. Is everything "grounded" right? I've seen a bad ground screw up the electronics so bad that the alt will burn out trying to keep up w/ the load. Just melt the coils right out.
3. How old is your battery? Because if your battery sucks your alternator has to work twice as hard and will eventually die out. I reccomend you purchase a new battery. Its more cost effective than a new alternator and when you do get a new battery check its status regularly. Like twice a week. Is the current still strong? Is it charging the way it should?
4. If you plan on upgrading your audio setup in the future you may consider a red-top battery. There a little bit more expensive but well worth it for high draw high demand systems. You can purchase them from most marine stores or directly from the manufacturur. I like Optimas battery's. Decent price good product.
Linkage Optima Batteries
12vdeej 
Member - Posts: 26
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Joined: July 04, 2006
Location: United Kingdom
Posted: August 06, 2006 at 4:44 AM / IP Logged  
If the amp is 700W rms, and class A (most likely), then at full power it will draw about 97 amps. If your alternator isnt powering much else then you should get away with it, but then of course your car does have headlamps, on board electronics etc, so you could be pushing the alt pretty hard. If you post the model number of the amp i can tell you whether this is actually the case, as i assumed a 700W rms output, when that may be the peak power and would definately not cause a problem.
12vdeej 
Member - Posts: 26
Member spacespace
Joined: July 04, 2006
Location: United Kingdom
Posted: August 08, 2006 at 1:09 PM / IP Logged  
I calculated the current draw by using power = volts x amps, and the fact that most class A amps are about 50% efficient. At 50% efficiency a 700W output requires a 1400W input. By rearranging the above formula, amps = power/volts ( 97 amps = 1400 watts/14.4 volts). Menaztricks, if you can verify that the amp is 700W rms, then the amp is definately your main problem. Additionally, i doubt the stock wiring in your car will be up to constantly carrying 100 amps or so. As desolationangel said, you should really upgrade the 'big 3'. Again, this all depends on whether your amp can actually give out 700W or not. The easiest way to find out the actual maximum output power is to look at the amp fuse rating(s).
killer sonata 
Silver - Posts: 718
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Joined: May 17, 2006
Posted: August 08, 2006 at 1:49 PM / IP Logged  
I doubt a bazooka amp will ever put out 700W lol. I definitely agree with everything desolationangel said. He pretty much nailed all the entry level stuff.
haemphyst 
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Platinum spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: August 08, 2006 at 3:41 PM / IP Logged  
700 watts with a good wax job, a long downhill, and a stiff tailwind, maybe.
Probably more on the order if 250 to 300 watts, if that much. It won't be a Class A amplifier, pretty much guaranteed. Class A/B, more likely, but still, IF it's recent enough, it could still be a Class D amp.
Class A is actually closer to 30-33% efficient, Class A/B is more like 55-66% efficient, and Class D can acheive 95% efficiency.
But, yeah, look at the fuses, add them all up, for total current capacity, multiply by 14.4, and then multiply by .3 for class A, .66 for A/B, and .95 for Class D. To save you the hassle, assume Class A/B. These formulae will give you the true, real-world continuous output, peak.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Flakman 
Copper - Posts: 365
Copper spaceThis member has made a donation to the12volt.com. Click here for more info.spacespace
Joined: April 25, 2005
Location: United States
Posted: August 08, 2006 at 6:23 PM / IP Logged  

I would go with desolationangel's number 1 selection. Upgrade the "Big 3". That in itself may take care of your problem.

I know better than to argue with haem's calculations. can this be overloading my alternator? -- posted image.

The Flakman
I feel strange. I have deja vu and amnesia at the same time.
John | Manteca, CA
12vdeej 
Member - Posts: 26
Member spacespace
Joined: July 04, 2006
Location: United Kingdom
Posted: August 09, 2006 at 12:42 PM / IP Logged  
haemphyst is right about the efficiency ratings, i was confusing class A with class A/B

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