FYI - High Output Alternator

[BigDaddy13440]

Having a charging problem with my XL lately, I think the alternator is working intermittently. It'll charge the battery while driving, but if the truck sits for more than 2 hours, my voltage is down to under 10, and I have to use a jump-pack to get it going. So, did a little research on alternators:

2004 GMC Sierra 3500 trucks have the exact same part numbers as ours for the factory 105 and 145 amp alternators. Advanced Auto and RockAuto both have an optional 253 amp alternator, new, for less than some of the remanufactured units at either place. Found mine on E-Bay, no core required and with shipping included, for $115 - at Advanced it was about $250!

https://www.ebay.com/itm/H2-Suburban-ALTERNATOR-253-AMP-97-98-04-HIGH-AMP-HD-High-Output/352212758226?ssPageName=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

I'm starting with the alternator, as I'd replaced my battery back in August. If the alternator is good, then I might have a bad battery. If that doesn't cut it, then I'm going to disconnect all my accessories and then reconnect them one at a time, until I find the culprit.

 

[iamdub]

If the alternator is charging and keeping the voltage around 14V while the engine is running, then it should be good. Sounds like the battery isn't holding a charge or you have something draining it very quickly. New batteries can be defective, especially if it's an Autozone house brand battery. You can quickly test the draw on the battery with a cheap multimeter.

 

[Doubeleive]

that's a decent price I paid $209 for a 300 amp a few months ago

 

[BigDaddy13440]

If the alternator is charging and keeping the voltage around 14V while the engine is running, then it should be good. Sounds like the battery isn't holding a charge or you have something draining it very quickly. New batteries can be defective, especially if it's an Autozone house brand battery. You can quickly test the draw on the battery with a cheap multimeter.

I had it tested, sat at 12V with the key off. 14.2V with the key on, and dropped to 13.4 with all my accessories on (including the stereo, with a Lightning Audio 1001.d mono amp).
The new battery is from Autoparet International, one of Advanced Auto's suppliers.

When the 253 amp alternator arrives, plan on doing dual batteries, with 1/0 wiring between batteries (also bought a 1/0 lug crimper) - already have the Big 3.

 

[iamdub]

I had it tested, sat at 12V with the key off. 14.2V with the key on, and dropped to 13.4 with all my accessories on (including the stereo, with a Lightning Audio 1001.d mono amp).
The new battery is from Autoparet International, one of Advanced Auto's suppliers.

When the 253 amp alternator arrives, plan on doing dual batteries, with 1/0 wiring between batteries (also bought a 1/0 lug crimper) - already have the Big 3.

Yup- sounds like the alt is doing fine. I'd make sure there's nothing draining it. Losing 2 volts in 2 hours is a big drain.

 

[SnowDrifter]

Pretty standard for ebay alts. Cheap high output alts are absolute dog shit. Get a good brand like Singer, Mechman, or DC Power. Pricey, but you get what you pay for

 

[BigDaddy13440]

Pretty standard for ebay alts. Cheap high output alts are absolute dog shit. Get a good brand like Singer, Mechman, or DC Power. Pricey, but you get what you pay for

It's not a cheaply-made, hopped up alternator meant for car audio. It's a direct fit for a Sierra 3500 series, it's an option available from the factory. Even if it ***** the bed in a year, I'm have it under warranty for that long

 

[rockola1971]

I had it tested, sat at 12V with the key off. 14.2V with the key on, and dropped to 13.4 with all my accessories on (including the stereo, with a Lightning Audio 1001.d mono amp).
The new battery is from Autoparet International, one of Advanced Auto's suppliers.

When the 253 amp alternator arrives, plan on doing dual batteries, with 1/0 wiring between batteries (also bought a 1/0 lug crimper) - already have the Big 3.

Nobody else caught this? Battery voltage was at 12v with key off but with key on the battery voltage went up to 14.2v? You have that backwards?

 

[iamdub]

Nobody else caught this? Battery voltage was at 12v with key off but with key on the battery voltage went up to 14.2v? You have that backwards?

I assumed by "key on", he meant with the engine running. The battery shouldn't be 14V by itself.

 

[BigDaddy13440]

I assumed by "key on", he meant with the engine running. The battery shouldn't be 14V by itself.

Yep

 

[Martinjmpr]

Was there an error message on the DIC? When my alternator went out in April I got a message on the DIC that read "Battery Not Charging." Was able to make it home (thanks to the dual battery!) and replaced the 145a alternator with a rebuilt unit from Auto Zone. Problem solved.

If there's no error message I'd suspect the battery, as others have said.

 

[rockola1971]

I would definitely suspect the battery since he said with key off it was at 12v... when it should be closer to 13v. If he is reading 12.0vdc then that battery isnt fully charged, has a load on it or has a cell(s) dragging the battery output down.

 

[BigDaddy13440]

It's barely been cranking over in the morning, at about 9-10v, temps have been in the 30's. Once running, the battery will charge enough to crank over almost immediately any time throughout the day, and stay at 12v+. BUT, I noticed over the past few days that running my stereo (only one amp, a 1000W), that even on a modest volume, the voltage drops from 14+ at 2000rpm to about 13v (and my headlights flicker), and when pushing that amp hard, voltage drops further, and my headlights and interior lights dim).

So yes, I'd also agree that it's the battery. But I also don't think the stock alternator is working at full capacity. So, I received the 253amp one yesterday, it's going in tomorrow. Bought a heavy lug crimper, going to re-work all the Big 3 wiring, and add the second battery. I do NOT want to have to worry about having no juice in winter here in NY.

 

[iamdub]

The stock alternator puts out ~105 to ~160 amps, depending on which one you have. The battery should be somewhere around 700-1,000 amps. In simple terms, the battery is what powers your stuff, the alternator just recharges the battery. If the vehicle has a large power draw on the battery, a larger alternator is needed to "power through" that draw to charge the battery. Yes, everything is pulling off the battery and the alternator at the same time, but the battery is what supplies the majority of the ampacity to maintain voltage. You don't want 100 amps (big stereo, winch, etc.) pulling on your alternator at all times.

 

[W8TVI]

The stock alternator puts out ~105 to ~160 amps, depending on which one you have. The battery should be somewhere around 700-1,000 amps. In simple terms, the battery is what powers your stuff, the alternator just recharges the battery. If the vehicle has a large power draw on the battery, a larger alternator is needed to "power through" that draw to charge the battery. Yes, everything is pulling off the battery and the alternator at the same time, but the battery is what supplies the majority of the ampacity to maintain voltage. You don't want 100 amps (big stereo, winch, etc.) pulling on your alternator at all times.

I've actually put a pair of DC amp meters on the main wires from the alternator and the battery, and I found that no amperage flowed from the battery until I exceeded what the alternator was rated for.

I was quite surprised, and double checked that I had the right wires.

 

[BigDaddy13440]

Ran it yesterday, sat from noon until 8pm tonight. Only draw visible is the blue LEDs under the rear seats, very minimal draw, and the phone charger (status LEDs).
Wouldn't start, had to jump it, voltGe was at 9.2V.

 

[Doubeleive]

from what you are describing that is a bad battery, lt may be just barely holding on enough to tease you to think its not. yank it and replace it or have it tested at the place of purchase. that's my .02 anyway from previous experience.

 

[BigDaddy13440]

from what you are describing that is a bad battery, lt may be just barely holding on enough to tease you to think its not. yank it and replace it or have it tested at the place of purchase. that's my .02 anyway from previous experience.

Have to agree.

 

[rockola1971]

The battery is junk. It should me at a min 10.5vdc while the engine is cranking. The battery voltage should be around 12.5vdc when fully charged at rest. The only purpose of your battery is to provide the high amperage your starter requires to spin the engine over for starting. After the engine is running EVERYTHING that draws power is being powered by your ALTERNATOR.

Why are you pissing around with a $70 battery that is bad? A battery is not rocket science and many have provided correct information concerning your battery being bad. (Granted some have provided some very ignorant info here too).

Ive troubleshot bad batteries on the F/A-18, F-14, SH-60 and you know what, they arent much different than a automotive battery. Aviation use AGM now but same principles.

A battery is actually an incorrect term. It is actually a Container, Case or Jar that has a collection of batteries (cells) within. There are 6 batteries (cells) within an automotive container ("battery"). Each cell (Battery) is charged to 2vdc+ (typically 2.08vdc+). If a "fully charged" automotive battery's voltage is much below 12.5vdc then there is a reason which is usually a cell (battery) not being able to charge up to or over 2vdc. This is a "dead cell" that is not pulling its weight. There are two factors that determine the amount of power a cell within an automotive "battery" can produce. Voltage and Current output. Power equals voltage times current. You have to have both. Since all 6 cells are in series the max amount of current output is equivalent to the lowest cells current output. The others cannot make up for the slacker. It is the opposite for voltage. Other cells can add to the total voltage output and pick up some slack of a weak cell but the amount is very limited.

 

[BigDaddy13440]

The battery is junk. It should me at a min 10.5vdc while the engine is cranking. The battery voltage should be around 12.5vdc when fully charged at rest. The only purpose of your battery is to provide the high amperage your starter requires to spin the engine over for starting. After the engine is running EVERYTHING that draws power is being powered by your ALTERNATOR.

Why are you pissing around with a $70 battery that is bad? A battery is not rocket science and many have provided correct information concerning your battery being bad. (Granted some have provided some very ignorant info here too).

Ive troubleshot bad batteries on the F/A-18, F-14, SH-60 and you know what, they arent much different than a automotive battery. Aviation use AGM now but same principles.

A battery is actually an incorrect term. It is actually a Container, Case or Jar that has a collection of batteries (cells) within. There are 6 batteries (cells) within an automotive container ("battery"). Each cell (Battery) is charged to 2vdc+ (typically 2.08vdc+). If a "fully charged" automotive battery's voltage is much below 12.5vdc then there is a reason which is usually a cell (battery) not being able to charge up to or over 2vdc. This is a "dead cell" that is not pulling its weight. There are two factors that determine the amount of power a cell within an automotive "battery" can produce. Voltage and Current output. Power equals voltage times current. You have to have both. Since all 6 cells are in series the max amount of current output is equivalent to the lowest cells current output. The others cannot make up for the slacker. It is the opposite for voltage. Other cells can add to the total voltage output and pick up some slack of a weak cell but the amount is very limited.

Can't exchange it.till.tomorrow afternoon.