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Discussion Starter #1
im looking into doing a few things on my zuk such as spotties, sound system, on-board air system... you get the idea. i know the stock alternator wont handle all of that simultaneously, and im trying to work out what size i am going to need... all easy enough to work out, what i really need to know is how many amps the engine uses to run... even a rough figure would be great, but at idle and at highway speeds would be great.
 

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Now you've piqued my curiosity! I'll try to make a measurement on my '93 EFI. I can borrow a trick clamp-on DC ammeter from work. I'm guessing 5-15A, and probably even on the low side of that.

I'd observe that most alternators are _NOT_ meant to provide full rated output all the time. They'll get too hot and burn up. The internal rectifiying diodes are a frequent failure point because of this heat. Early Zuk alternators were 45A-rated, but around '90 the rating was increased to 50A, according to my 1990 Supplementary Service Manual, p10-1.

Edit: I measured some currents today on a charged battery and warm engine at idle, stock '93 Samurai electrical system (but not for much longer).
11.5A out of the alternator, 5.5A into the battery, giving about 6A for the rest of the vehicle, including EFI (lights and radio off).
On low beam, about 22A out of the alternator, 4.5A into the battery
On high beam, about 25A out of the alternator, 4.5A into the battery (using H6024 halogen sealed beams)

The meter was a Tenma 72-6185, calibration date uncertain. Readings were averaged by eye. So take these numbers with a grain of salt.
 

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Discussion Starter #3
i just realised i didnt even mention vehicle type! sorry! its a stock 94 sierra/samurai with carby 1.3L... so its quite low power consumption. Thanks!!!
 

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Now you've piqued my curiosity!
Congratulations!!!! You're the first person I've seen in a LONG time to spell that word correctly.

On topic- I'm going to be in the same boat soon as I want to put some spot lights on mine. I use it for coyote hunting in the winter and am often driving back home on dirt roads at night. I'd like to have some light.
 

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10-15 amps for a set of lights is about right. The carburetted SJ413 is going to be about 5 amps less than the Throttle body injected rig. The big drains are aftermarket sound systems with big subs and drivers. Things like winches are not constant use devices and your battery should provide enough power for running one short term, and a second good deep cycle battery will provide enough power for longer pulls for those that use the winch more frequently.
 

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and remember LED tail and brake and side marker lights cut things down quite a bit.
I've found most of the time when someone asks a question like this they need a 'bigger' battery. IMHO
 

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for a winch, yeah. Bigger battery or more batteries. For a light rack or a giant sound system that has a constant draw, bigger alternator. I put a CS130 alternator (105 amps) in my samurai. The bracket from trail tough is 25 bucks, the alternator was 40 bucks. It used the stock upper bracket and belt. Runs like a champ and havn't had any issues with it yet. I can't see ever needing any more power than that unless you were running an onboard welder... (oh what dreams I have of onboard welders)
 
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