At what point is an alternator upgrade necessary?

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Say a person has a stock vehicle with a 160 amp alternator, but wants to add 2 100w auxiliary lights. Would an alternator upgrade be necessary?

I personally ran my stock 130 amp alternator when I added my 100w IPF's with no issues. I did however do the 160 amp 2006 Durango upgrade when my alternator went out. The ~$60 discount and surplus power was a no brainer IMO.
 
Switch to LED and you will have more light with less energy consumption. There are some very nice lights and the price has come down. I replaced the 2 55w lamps on my Wrangler with an 18" bar and its like daytime when the bar is on.
 
Originally Posted By: 64bawagon
Switch to LED and you will have more light with less energy consumption. There are some very nice lights and the price has come down. I replaced the 2 55w lamps on my Wrangler with an 18" bar and its like daytime when the bar is on.


It's for my brother's Jeep and he personally finds those very distasteful.

Just thinking out loud, he did install some Quadratec LED headlights because the OE's were pretty sad at night. Maybe this did the alternator some favors thus leaving more capacity for the upgrade.
 
The 100 watt lights would take nominally 8.3 amps each. (8.3 is 100 watts divided by 12 volts.) Worst case still less than 10 amps each if he is able to get more than 12 volts to the bulbs.

So this mod would add about 20 amps. There is still enough power from the stock alternator, especially as the regular lights use less.
 
Not yet. If he's going to be doing some weird camping thing with tons of idling and the lights on he should check ratings at idle. Beware the stock alternators are wound better for idle output than many aftermarket hop-ups though.

I suspect this car still has the factory alternator... it'll be up there in the revs, the lights aren't all on forever, and the battery can carry a deficit briefly:

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I'm not 100% sure, but a little extra amps in reserve never hurt nobody...

I took my Camry from the factory (and probably tiring) 100 amp to a 130 amp reman that's a drop in upgrade from a Sienna

I thought it prudent with HID's, heated washer fluid, a small sub, time's of extended city traffic driving and remote starting, planned heated/cooled seats

Even offsetting this with many LED bulb replacements, I feared running out of electricity

Now I have ~14v+ at idle most times, which wasn't possible in the past, and loads like window and seat motors don't dim the lights like they used to


TL:DR, Your milage may vary
 
Originally Posted By: dlundblad
Say a person has a stock vehicle with a 160 amp alternator, but wants to add 2 100w auxiliary lights. Would an alternator upgrade be necessary?


Abolutely not! 160amps is a beast already, a couple of 100W lamps shouldn't even make it flinch.
 
130+ Amp alternators are usually fine in most cases. Of course it's always best to do the electrical math (add up your loads) so the definitive answer is to do that and you will always know for sure.

Just like with your electrical panel / breakers at home, you only need to account for simultaneous use, with vehicles you should spec out the night time use with lighting assumed on and account for air or heater being on.

For basic loads keep in mind that a carb equipped OEM vehicle usually came with a 65A alternator in base configuration (eg GMC / Chevy pickup). Supplemental lighting (fog lamps, off road lamps, beacon lighting) would usually result in an upgraded alternator from the OEM. Modern engine electronics would add 10A maybe. Car Audio can be a power hog. Go from there for your "back of the envelope" calculations.

Watts = Volts x Amps

Assume 14.5V (charging load) for automotive use.
 
Really need to know what the other draws are.

200w at 12v is about 16-17 amps (doing the math in my head here)

If you are no where near the 160A capacity of the existing alternator, you probably don't need an upgrade.

The answer really depends on the total load on the alternator. We can't tell you what adding another 17A of load will do without knowing what it is already asked to provide.

Originally Posted By: dlundblad
Say a person has a stock vehicle with a 160 amp alternator, but wants to add 2 100w auxiliary lights. Would an alternator upgrade be necessary?

I personally ran my stock 130 amp alternator when I added my 100w IPF's with no issues. I did however do the 160 amp 2006 Durango upgrade when my alternator went out. The ~$60 discount and surplus power was a no brainer IMO.
 
Originally Posted By: PeterPolyol
Originally Posted By: dlundblad
Say a person has a stock vehicle with a 160 amp alternator, but wants to add 2 100w auxiliary lights. Would an alternator upgrade be necessary?


Abolutely not! 160amps is a beast already, a couple of 100W lamps shouldn't even make it flinch.
+1
 
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