i know, i still plan on getting either a stinger 400 amp or getting 2 200 amp alternators. i understand exactly what your talking about, if your pulling more power than what the alternator can produce then your battery will go dead. just the same as if you dont crank the truck and listen to the radio, the battery isnt going to charge itself.

 

ok so do me a favor and put a amperage clamp on your alternator wire going to the battery with the engine running at idle and turn on all your accesories and record the amperage for me and the voltage at the battery so i can see what a properly operating alternators voltage and amperage output is supposed to be. after you do that clamp all the positive wires going from the battery under the hood that go to any accesories that youve added to it and the factory computer and post the results for me to see.

 

Here are some results I got from my 08'. Alt HOT at idle. NOTE: Not stock alt, battery or sterio. Manufacturer rated alt @220 tops and around 150 at idle. Battery is an Optima yellow top group D34/78. Sterio amps running 1000 watts rms. Wish I had a carbon pile to fully test alt output.


Amp output from alt. Engine on, all acc and sterio off. No pic of volts but was between 13.8 and 14.0.


Amps output from alt. All acc on ( head lights on high, fogs on A/c on high), sterio off. Volts still around 13.8.


Max amps from alt with all acc on and sterio cranked.


Min volts at battery. All acc on and sterio cranked.


Min volts at power point in dash. All acc on and sterio cranked. Took about 10 minutes to drop this low. Raised idle to 1000 RPM's and volts began to climb.

 

And YES my head lights do dim with the sterio cranked. But only when at a stop light at an idle. Raise idle to about 1000 RPM's and they no longer dim.

 

90 amps is about what mine is putting out at idle with just the a/c, aftermarket fans , and lights on. hmm so i guess its about right for a stock unit. what does everyone else think? is my stock alt with 40k miles on it failing?
thanks 4 the post 4rd4life

 

I am just curious as to how many amps do your e fans pull?

 

around 25 amps there wired to come on with the a/c compressor and when the temp gets hot enough on the radiator to make the stock belt driven fan switch to high speed mode around 196 degs. ill put up pics and vid in a lil bit its uploading

this is the static voltage of the batts this truck hasnt been cranked or run in 3 days.



here are the vids.
http://www.youtube.com/watch?v=CSpcZfxTRP4
the 2nd one about 10 minutes have passed in between the vids.
http://www.youtube.com/watch?v=HG5oRvNHd7A

alt cold at idle around 94 amps of output loaded.
alt hot at idle under 90 amps voltage low at 2k 120 amps and reved to 4500 rpm 128 amps looks about right for a stock 130 amp alternator.

 

jrfonte, I'm interested to know how you wedged the two batteries in the stock location. I really need a second battery to run radio (ham) equipment. Will use a relay to isolate. I just had not seen a two battery setup like that. I was thinking about a second battery under the bed or in the bed, but your setup is much cleaner. Did you have to build a new tray? I understand your delima on the alternator current issue. I don't think I'll have that issue, I just need an isolated second source so my primary battery will still crank the truck. Thanks.

 

here is the thread on the batts me07xlt
https://www.f150online.com/forums/ot...tion-07-a.html

i dont have any isoloators on mine there just wired in paralel but it would not be hard to put one on them i just dont have a use for one. i used 34 bci sized batts they are just a little larger in length wise than the stock motorcraft batt but if you get a battery that isnt as wide then you probally wont have to move the washer bottle like i did to make them fit but it took me around 2 hours to fab it up i had never seen 2 of them in this location before when i did this and so far styxnpix has the only other one that i have seen on here.

 

My plan in the future is to run dual batterys and dual alts. my setup was goin to make bracket for a second alt then run the both wires strait to the battery in my toolbox. then have my reg battery for my starter, lights, ect.

 

So the one in the toolbox will just be a spare? You'd swap it into the front location if the main battery dies?

 

lol i would assume the accessories and such would be tapped into it as a stand alone add on with an independent charging system.

 

No one has a dual alternator set up yet?

I have been to two different Ford parts counters. I have asked a Ford mechanic, without any additional detail.

I'm still looking.
Eventually, I want dual alternators and multiple batteries.

Let's keep the post alive.

 

no i want to put 3 amps in my truck and spot lights so i plan on putting one in a toolbox for all the extra power i dnt want my truck to die if im out wheelin.

 

tcm
An extra battery won't give you any 'extra power' for things that run continuously. The extra battery in diesels is for extra starting power (momentary until the alternator starts working). An isolated 2nd battery is a backup in case you kill the first one. But running a battery wire through sheet metal & tool boxes is dangerous because there's no fuse in case the metal cuts into the wire. The battery can explode if there's a short. Also, any lead-acid battery (including AGMs) needs ventilation. If you keep it enclosed in a tool box, all your tools will be corroded by the acid vapor.

If you need more power all the time, then you need more alternator output (a bigger alt or a 2nd alt). But I doubt you need more. Check the typical current draw (NOT peak) for your amps, and I bet you'll find the stock alternator is enough.

Tt
Why? What 'additional detail' are you after?