Higher output alternators?

chino1969

chino1969

TJ Addict
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1) Is it necessary to replace a stock 117 amp. alternator with a higher output one when running driving lights and other accessories? 2) If so, will a higher output alternator affect computer or other sensitive electronics? 3) Lastly, what would those with experience recommend? Right now I have driving lights with their own relay, fuse and toggle switch. I intend to add back up lights and fog lights with their own dedicated circuits as described. Any thoughts/experience would be appreciated.
 
No need unless you start adding lots of extra lights, amp, winch, etc.
 
There's no need whether you have extra lights or winch at all. The vast majority of us with winches, etc. are running the factory 117 amp alternator, me included and I use my winch a lot. Better to just adhere to good battery management techniques like giving the battery and alternator a break once in a while if you have repeated long winching jobs which are actually quite rare. Not even a 160 amp alternator can keep up with the amps drawn by a winch under even a moderate load.
 
HO alternators are used for very high current/power applications. Except for the winch, you probably won't have a high power draw in your jeep. Examples of common high power electronics include power inverters, very large stereos, and welders.

The only advantage of a HO alt for most Jeepers would be to run the winch at charging voltage instead of battery voltage. Most winching operations take between 50 to 500 amps depending upon line load. A 370 amp alternator can provide between 230 amps (idle) and 380 amps (~2500 rpm). Any time the winch draw is less than the output of the alternator, the winch will be operating at charge voltage, or about 14.4 volts. Any time the winch exceeds the current the alternator can supply, voltage drops to 12 volts or lower.

The result of the voltage drop is significantly lower line speed. For most people, this will not be an issue. For the competitive, or the impatient, this may be an issue. When the lower line speed becomes an issue, then it might be time to consider a HO alt.

Should you purchase a HO alt larger than ~200 amps, look at the 3 following companies:
  • DC Power, Inc.
  • Singer Alternators
  • Mechman alternators
I recommend DC and Singer over Mechman but any of them are reputable companies especially in the car audio world. I have had great experience with Singer myself.

All 3 of those companies will build alternators up to 370 amps that bolt into our Jeeps with no modifications except for the Big 3 wiring upgrade. With a 370 amp, 2/0 AWG is usually recommended. For smaller alts, 0 AWG or even 2 AWG can be sufficient.

Be aware a 370 amp is going to run you about $900, and a 270 amp will run you around $600. Good products aren't cheap.

As a more budget friendly option, the Durango alternator upgrade is a good thing to consider. A reman Durango alt, which I recall is about 160 amps, can be found on the order of $150.

Unless you're serious about winching fast, welding, blasting 130dB+ tunes, or running a 3000 watt inverter, I would stick with the Durango alt, or even the stock alt.
 
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The stock alternator will replenish your battery just fine for most applications. If your charging system is taxed by heavier loads, I'd recommend investing in a better battery or even batteries. Big lights are only used at night, my guess is most people wheel mainly during the day. Recovery winches draw heavily, but that should not be an all day event. I'd wager in my Jeep the 2 amps for the stereo are my biggest continual draw and the stock charging keeps up just fine. I do not use the stereo off road so a 117 amp charging system is plenty healthy.
 
Jerry Bransford said:
There's no need whether you have extra lights or winch at all. The vast majority of us with winches, etc. are running the factory 117 amp alternator, me included and I use my winch a lot. Better to just adhere to good battery management techniques like giving the battery and alternator a break once in a while if you have repeated long winching jobs which are actually quite rare. Not even a 160 amp alternator can keep up with the amps drawn by a winch under even a moderate load.
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Thanks Jerry. There are too many products out there not really required that are hyped up to sell. I don't mind spending money for the right equipment but practicality is the motivating factor, not show.
 
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Jerry Bransford said:
There's no need whether you have extra lights or winch at all. The vast majority of us with winches, etc. are running the factory 117 amp alternator, me included and I use my winch a lot.
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Does anyone know if ALL TJ‘s came with the 117 amp alternator? Even the SE models? Even the ugly duck year of 1997?
 
IIRC the Tomb Raider edition came with a 136 amp alternator as part of the 'Tomb Raider Group' probably to help handle the incandescent light bar?
 
SSTJ said:
Does anyone know if ALL TJ‘s came with the 117 amp alternator? Even the SE models? Even the ugly duck year of 1997?
Click to expand...
Most TJs came with the 117 amp alternator (I've not heard of a higher amp alternator on a TJ). The only TJs that came with the standard 84 amp alternator were very stripped down models, mostly those without A/C.
 
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