Newbie w/ 200amp alt question.

[Phatsub]

Hello all, great site. I have an 01 Chevy Suburban with a yellow-top Optima battery that needs to be jump-started almost every time. It has a 200 amp alternator that was installed by a local shop that for many reasons, I will not ever go back to for any type of service.

Anyhow, when testing the alt, I get a 14.4 reading @ 2500rpm on the voltmeter. I don't know what the numbers should be or if the problem might even be the battery, which is about a year old. This is the third Optima since the alternator install, they've only been lasting about a year.

Did my local garage scam me somehow? Any help will be greatly appreciated.

Thank you.

[drew]

It sounds to me like the alternator in question is probably not producing very well at idle. 14.4v is a good charging voltage, but 2500RPM seems a bit high for the base line. A lot of shops will upgrade the output of an alternator by using less wire in the stator. This makes it produce fine at speed, but not at idle. You might have to upgrade to a double wound stator, which will have much higher output at idle. Your battery may also be to blame, optima yellow top batteries are deep cycle, meaning they can never be truly charged by a vehicles alternator, they need a slow, 24-hour recharge every so often to maintain starting power. If this is not done, the battery life will suffer tremendously.

[Phatsub]

Thanks Drew, you answered several questions for me. I'm looking at the Extreme Duty Dual Rectifier Alternator, is this the one that would work for me? I'm thinking 250 amp.

[drew]

That is the alternator I would recommend, the extra rectifier really improves the durability of the alternator. http://alternatorparts.com/Extreme%20Duty%20Dual%20Rectifier%20CS-144%20type.htm

[Phatsub]

So Yesterday I called in and ordered that alternator, and the gentleman on the phone suggested a second cable going directly from the alt to the battery. Can someone please explain this to me, like would it go to the positive or negative post, and what does that do exactly? Thanks.

[Phatsub]

Are we allowed to bump our threads?   I'm still looking for some help.

[drew]

You should connect a second 4 gauge battery wire from the positive alternator post to the positive battery post and a supplemental 4 gauge ground wire from the case to the negative battery post. This is just to insure that the alternator maintains good ground and the charging power gets to the battery with little resistance.

[Phatsub]

Thanks Drew, any pictures or illustrations to show this? Would the second ground cable attach at one of the alternator mounting bolts and run to the ground post of the battery?

[drew]

The second ground cable can go just about anywhere on the case of the alternator, a mounting bolt would be a good spot. We don't actually have any graphics on this, but I could probably draw a diagram.