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Old Feb 13, 2006 | 06:01 PM
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alternator output question

was wondering if i put a 1200 watt power inverter on my truck ,would it be to much for the stock alternator? if so what route could i take?.........thanks
 
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Old Feb 13, 2006 | 06:09 PM
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Originally Posted by yard_dawg
was wondering if i put a 1200 watt power inverter on my truck ,would it be to much for the stock alternator? if so what route could i take?.........thanks
Your going to have to look at the 12vdc input amp rating at max ouput of the
inverter(1200Watts)...should be in the specs. Then look at the nomminal output
rating of the alternator(in the manual specs). Of course u have the option of going to a larger alternator or dual alternators. What do u need that much
wattage for?
Nut
 
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Old Feb 13, 2006 | 06:12 PM
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Originally Posted by yard_dawg
was wondering if i put a 1200 watt power inverter on my truck ,would it be to much for the stock alternator? if so what route could i take?.........thanks
It's basic math. A 1200 watt inverter at RMS will put out 10 amps @ 120vAC which will draw about 100 amps @ 12 vDC... I believe a stock alternator puts out 110 amps at full power.... So that'll leave 10 amps for your engine, charging system and all your accessories. I'm not sure what your system draws, but more than likely you'll be dipping into your battery reserve (if running the inverter at full power). If you're just running a laptop (1 amp @ 120vac = 10 amps @ 12vdc) you'll be just fine.
 
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Old Feb 13, 2006 | 06:19 PM
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Originally Posted by cgl
It's basic math. A 1200 watt inverter at RMS will put out 10 amps @ 120vAC which will draw about 100 amps @ 12 vDC... I believe a stock alternator puts out 110 amps at full power.... So that'll leave 10 amps for your engine, charging system and all your accessories. I'm not sure what your system draws, but more than likely you'll be dipping into your battery reserve (if running the inverter at full power). If you're just running a laptop (1 amp @ 120vac = 10 amps @ 12vdc) you'll be just fine.
Just to be on the safe side, you should always add some, around 5-10%. Figure on it drawing at least 110 amps from the alternator. If you'll be using this constantly, it might be worth looking into the second alternator.
 
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Old Feb 13, 2006 | 06:20 PM
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Originally Posted by cgl
It's basic math. A 1200 watt inverter at RMS will put out 10 amps @ 120vAC which will draw about 100 amps @ 12 vDC... I believe a stock alternator puts out 110 amps at full power.... So that'll leave 10 amps for your engine, charging system and all your accessories. I'm not sure what your system draws, but more than likely you'll be dipping into your battery reserve (if running the inverter at full power). If you're just running a laptop (1 amp @ 120vac = 10 amps @ 12vdc) you'll be just fine.
Your right there cgl...Watts Law ....but i would like to add that there is some aditional conversion losses to account for so i would add some more amps to the total picture.
Nut
 
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Old Feb 13, 2006 | 08:45 PM
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Originally Posted by twags6
Just to be on the safe side, you should always add some, around 5-10%. Figure on it drawing at least 110 amps from the alternator. If you'll be using this constantly, it might be worth looking into the second alternator.
Yes. If you are drawing 110 amps from an alternator that puts out 110 amps.. goodbye batteries!

Originally Posted by PSNut
Your right there cgl...Watts Law ....but i would like to add that there is some aditional conversion losses to account for so i would add some more amps to the total picture.
Nut
I agree. Assuming the charging system is running correctly, it'll put out 13.8 - 14.4 volts, so that'll complicate the equation as well. It really depends on what you'll be running with the inverter. The Inverter does comsume a small amount as well...
 

Last edited by cgl; Feb 13, 2006 at 08:47 PM.
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Old Feb 13, 2006 | 09:03 PM
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Originally Posted by yard_dawg
was wondering if i put a 1200 watt power inverter on my truck ,would it be to much for the stock alternator? if so what route could i take?.........thanks
I'd get a high output alternator, don't forget not to skimp on the power wires to the inverter, if you run at full capacity of the inverter, we are talking some major amps here for extended amounts of time. Check ebay, there are a couple of 200A models and some 170 as well. there is also some pretty good deals on cable as well. Depending on leghth of run, i'd run 2/0 or 3/0 cable to your inverter. Then again, I'd also seperate the circuit completely and have a couple of deep cycle batteries as close to the inverter and do a dual alt setup.
 
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Old Feb 13, 2006 | 09:20 PM
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I dont think that you can practically run a 1200 watt inverter at full max load in the truck for long. 30 minutes or so, maybe.

It is too close to the engineering limits of many components. Your better bet may be a second alternator or a bank of batteries. The batteries do have to be charged, eventually.
 
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Old Feb 13, 2006 | 09:36 PM
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Just a note, I beleive the stock alternator puts out 130 Amps. I was doing some headlight/fog light calculations today so that is how I came across that figure. LOL
 
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Old Feb 14, 2006 | 10:47 AM
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Originally Posted by goldman
Just a note, I beleive the stock alternator puts out 130 Amps. I was doing some headlight/fog light calculations today so that is how I came across that figure. LOL
I thought this too, untill I was told otherwise. It seems there was a 95 through 115 available in 99-01. A 110 in 02 & 03. And the 6.0's have a whole different combo. Here's what I found OEM from Ford Parts Direct....


 
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Old Feb 14, 2006 | 03:31 PM
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thanks for the input guys. no i will never use the inverter at full power. jsut got a heck of a deal on this one. going to use it for things like camping and stuff like that.
 
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Old Feb 14, 2006 | 04:18 PM
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I would still but in some aux batteries w/isolator so you can use the inverter without concern of the truck starting. I built a battery tray that mounts to the frame rail underneath the bed on the passenger side. Right now I only need one battery but was going to put two in there when I was going to get a slide in camper, then we got a 5th wheel and don't really need it but it is sure nice to have to hook all my accessories to. I have a small 350W inverter for lights and Lap top.
 
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