100,140,160 output alternator's. Can you have too much?

[sponsoredbydad]

I am needing a new alternator. Running extra off road Hid's, stereo stuff, fuel pump, has killed 2-86amp alternators each lasting about 1yr ea. I'm going to install a 2nd battery to help split the load, can you have too much amp output?

 

[dyeager535]

The alternator (unless failed) only puts out what the requirements are. So no, you couldn't put too large of an alternator on.

As is my theory with batteries though, paying 4 times the price, for capacity you will never use, is pointless. However it is better not to run things on the ragged edge of failure, as you simply push them harder potentially causing rapid failure. If you can get an ultra high capacity alternator that has done really good for people, for a price that is equivalent to anything else out there price-wise, no reason NOT to of course.

You need to determine the maximum draw from everything on the truck to properly size the alternator.

 

[sweetk30]

I have been running a 210amp aftermarket for over 8 years no problems .

only puts out what it need to .

plow truck with live hydro NOT electric plow pump . with all truck running / heater on high / wipers / and 50-60 amp draw of full light bar on top / tbi injection it would kill my batt 1000ca and start droping off the amps / volts in less than 30 min with a 100 amp stocker .

swaped to the 210 amp unit and never 1 problems since then .

 

[79rustyk10]

I'd get the highest amperage rating available unless added cost came into play. Where are you getting them from? The part store remans I've dealt with have usually been junk , just curious if it's a quality issue vs lack of output.

 

[MrSchaeferPants]

You need to determine the maximum draw from everything on the truck to properly size the alternator.

This

And make sure you have adequate grounding, and proper gauge wiring. Make the alternator's job as easy as possible. That much juice, nothing stock on that system was meant to handle those requirements. So if your power comes through any wires like the junction block's power supply, it's not big enough. Also, the larger 86amp alt may want a larger output wire, so if you're using the stock one, I'd think about upgrade it.

Plus, your current alternator IS a 3 wire properly hooked up right? The field/excite, and voltage sensing (going to a junction block)

Where are the add-ons wires getting it's power from?

 

[sweetk30]

I got mine from these guys . http://www.ebay.com/sch/alterstart/m.html?ssPageName=STRK%3AMEFSXS%3AMESOI&_trksid=p2053788.m1543.l2654

and also did the 2ga or 0ga ( cant recall size ) output wire upgrade from alt stud to battery . made my own for this .

here is the one I am running with my serp belt setup http://www.ebay.com/itm/90-95-NEW-C...r_Truck_Parts_Accessories&hash=item1e53e55754 shows 200amp . but dyno sheet showed just over 210 amp act output. and up to 120 amp at 800rpm

 

[sponsoredbydad]

Thanks . I'll need to go re-check my wiring. I may have run it in a inefficient way trying to make it easier to get to all the accessories. I will also try to figure out what I'm pulling. Everything is connected straight to the battery and from what i just read that is not the best way to do it.

 

[MrSchaeferPants]

Everything is connected straight to the battery and from what i just read that is not the best way to do it.

Well, at least with it connected to the battery you don't have the issue of old under gauge wires not meant for those things, but it does make wiring at the terminal a rats nest. One of these would be a good idea, mount it on your firewall, you can replace the one that's currently there.



But the positive is only half the equation. How are the stereo and HIDs ground connected, body? And does the stereo have a big ol' amp? Don't forget to check the cab/chassis/engine ground straps. Just thoughts, I had a K5 with a stereo (although no amp) and 4 halogens on a bar and a few other things running off the stock alt w/o a problem.

 

[Mastiff]

I got a Powermaster 140 amp and would go higher if I had it to do again. I added Windstar electric fans and halogen headlights wired for all 4 to come on at once. When all the lights and all the fans are going, I'm not at full charge at idle. This shouldn't come up very often, but I'd feel better if the system could handle it.

 

[ktmoutfront]

I had a custom wound one made 9 years ago. 85 amp at idle and 200 amp max. One battery. Never an issue.

Watch, that will change now.

 

[bp71k5]

I've read some of the specs for these alternators that say they have a duty cycle of 80%. Is that a common feature for alternators? I'm wondering if I should add a 20% buffer to my power load estimate when choosing an alternator.

 

[dyeager535]

I suspect the main reason why GM sized the alternators as they did, was simply idle output. The SI-series had pretty bad idle output numbers, which was apparently somewhat rectified with the CS-series. Even then, as already mentioned here, idle will be a problem if load is fairly high at idle. Somewhere I've seen the output charts, but it may have come with the alternator, and who knows if that was realistic.

GM was installing 80+ amp alternators on the full size cars back in the early-mid-80's, when even the most optioned out cars couldn't use anywhere near that much. The duty cycle is probably part of it, but so was the idle output.

 

[bp71k5]

Seems like a reasonable answer and happens to match what I see with my 96 amp 12si. It powers everything fine at speed, but I can see the volt gauge drop to 12ish volts when headlights and cooling fans are on at idle.