Unca_T

Hey Gang-
Does anyone know where I can look to find the voltage output of a factory alternator on my 2001 Chevy Express 1500 5.7 liter V8?
I've gutted it and have been converting it into a camper van. I will be using the alternator to charge the 100 AH deep cycle battery
used to power the "house" stuff. This is my first time doing this sort of thing so I'm trying to get all my ducks in a row.

Thanks for any thoughts.
Peace
Unca_T

Twscarp

Try using this from RockAuto, it lists the amp output of all that are available.

2001 CHEVROLET EXPRESS 1500 5.7L V8 Alternator / Generator | RockAuto

canucklehead

You can have it bench tested at a shop that rebuilds them. I had mine done on my 2002 and under full load it went up to way over 100 amps. I was surprised.

tech2

if its voltage your worried about for your agm battery; that info can be hard to find. In general most are regulated to 14.2 to 14.5 but this can vary with battery state of health. put a voltmeter on it and take some measurements under varying load condtions. agm batteries can charge for short times over 14.4 but not more than 1 hour.
they may be something at an rv center for controlling charging voltage. Put an isolator to protect your service battery from being drained when the vehicle is off and the agm battery is in use.

lunghd

Get a proper dual battery charging kit and DO NOT wire them directly in parallel. The kit will charge your primary battery & 'top off' the secondary battery as needed while keeping them isolated if you leave your dome lights on or one fails with a dead cell etc. There are many great kits out there but here is a generic search result from Amazon to give you an idea what to look for:

Dual Battery Kits

You may be able to find them locally at RV shops or off-road equipment shops.

Some folks use dual hard-wired parallel batteries for certain applications but it's a bad idea for most.

David Elliott

Sorry to be this late, but maybe somebody will need the info..
From 88-02 most stock GM truck alternators were either 105 or 155 amp. The 155 was used for hd trucks and premium trim packages to handle extra accessories and lighting. They're all some variation of a Delco-Remy design, but may be made by Delphi or a few other suppliers. But since they're all the same design, you can tell by looking at them which one they are. The 105 is physically smaller, with only about a 1/16" spacing between the front and back of the alternator. Because the 155 has more windings it's closer to 1/4" between the two halves.

Gumby22

That’s good info to have - thanks. Does that hold true for reman or new aftermarket alternators?

David Elliott

Yes it should, with a reman the spacer stack doesn't change. And with new aftermarket it still holds true because of the side needed to hold the larger winding bundle as amp capacity is increased.


The first picture is a 105 amp Delphi currently attached to a junk 2001 4.3 GMC Safari in my back yard. It's hard to see from the corrosion, but there is only a 1/16" gap between the housing. The second is from a 2001 Chevy Express 3500, just removed and replaced two days ago. It was a Delphi 205 amp according to Collins Bus ( my Express is a short bus), but it was the factory original for the hd trucks. It has 3/4" spacing and is identical to the 255 amp Powermaster aftermarket alternator I replaced it with.
I wish I had a 155 to show, but the moral is all those GM / Delco Remy style alternators follow the same rules, even reman and aftermarket.

David Elliott

This is the best reference I can quickly find. This is a Reman 150 amp Delco. You can see the spacer stack is much narrower than the 205 Delphi I showed above. If memory serves, it's around 3/8". I've been working on Chevy's since I was a kid, my old man passed the cursed disease to me. Over the last six months converting the bus to an RV I searched all over the web trying to ID that 205 alternator from above. Never got help to ID it till I called Collins. The 105 /155 info from a came from a retired GM service tech, and the spacing thing happens to line up with all the alternators my hands have touched for 4.3s, 5.3s, 5.7s through the years. Hopefully it'll help somebody.

Gumby22

That’s very helpful to me at least - thank you. I work at an independent shop but at least 1/3 of our customers have GM trucks in the 1988-2002 range. It’s always frustrating trying to ID the alternators because any info to do so is usually missing. I never considered that the spacers indicated the rating until I read your post and then it just clicked - Captain Obvious rides again!