Alternator Question

[Copasetic]

This may sound a little stupid but I have a 140 amp battery isolator and running dual batteries. I'm wanting to have my alternator rewound and upgraded. Would it do me any good or would it hurt anything if I were to go higher than 140 amps? I have only my truck running off of the main battery and I have all of my accessories running on the second. (amp, lights, winch, about to be dual fans, dual line locks, remote winch on the rear, and would like to have a decent sized power inverter in the back eventually and maybe even on board air) Thoughts?

 

[lectric80]

In the ones that my buddy built, it really isn't worth upgrading beyond 140 on a stock alternator. The ones that are available in higher outputs, have upgraded internals beyond just being rewound. They tend to not last nearly as long, and are pretty pricey to rebuild. A buddy of mine runs a 200 amp on his Sub, but only has a life expectancy of one to two years.

 

[Copasetic]

In the ones that my buddy built, it really isn't worth upgrading beyond 140 on a stock alternator. The ones that are available in higher outputs, have upgraded internals beyond just being rewound. They tend to not last nearly as long, and are pretty pricey to rebuild. A buddy of mine runs a 200 amp on his Sub, but only has a life expectancy of one to two years.

Wow. So would it hurt anything going over 140 with my current isolator? Or would I just be better off having mine punched out to 140 and call it good? I'm thinking that's the route I'm going to take because I've heard having mine rebuilt would be a lot cheaper than going and buying a new HO alt.

 

[lectric80]

New HO alternators are very pricey. Well into the 200 to way more range. Most likely it wouldn't hurt the isolator, since not all of the amperage is going to go through it, but I wouldn't recomend exceeding the limitations. I would say punch yours to 140 and call it good. Even with the amount of lights you have, under most circumstances you aren't going to need everything your alternator can put out. The batteries can take some of the load short term, and the alternator can compensate once the load drops.

 

[Copasetic]

New HO alternators are very pricey. Well into the 200 to way more range. Most likely it wouldn't hurt the isolator, since not all of the amperage is going to go through it, but I wouldn't recomend exceeding the limitations. I would say punch yours to 140 and call it good. Even with the amount of lights you have, under most circumstances you aren't going to need everything your alternator can put out. The batteries can take some of the load short term, and the alternator can compensate once the load drops.

True and thanks! It's not like I'll be running all 14 lights, winching someone out, and blaring the stereo all at the same time. I just didn't want to take the chance of frying my isolator if I went too big on the amperage. Sounds like I need to make me a phone call tomorrow.

Oh yeah, when I go to run the power cables for my rear winch (portable M8000), would it be ok if I just run 1 hot wire to the the back from the battery and have a short one grounded to the frame? Say on one of the bumper brackets, or does a winch need both polarities connected to the battery?

 

[lectric80]

You can ground to the frame, but I highly recommend adding a ground cable from the battery directly to the frame. This will ensure positive ground for the winch. There is no real need to run the heavy cable all the way back to the front, as DC really doesn't care as long as there is plenty of ground capability. I would run like an 8 or even 6 gauge cable direct to the frame from the battery, then an 8 or 10 at the winch.

 

[ryoken]

For any non-welding rig, 140 is plenty imo.... The jump from 140 to 200 is pricey.... And considering how nice it is to keep an extra, equal alternator in the parts crate, can make it especially expensive in the end...

Gonna be quite some time till I get welding capabilty.. Those units are SERIOUS coin.. priority #63.....

 

[Copasetic]

You can ground to the frame, but I highly recommend adding a ground cable from the battery directly to the frame. This will ensure positive ground for the winch. There is no real need to run the heavy cable all the way back to the front, as DC really doesn't care as long as there is plenty of ground capability. I would run like an 8 or even 6 gauge cable direct to the frame from the battery, then an 8 or 10 at the winch.

Good deal. When I installed my second battery I ran a 10 gauge wire from the neg side to the body and then a 4 gauge directly to the frame so I should be good there. I'm going to call a couple of welding supply shops to check out there prices on their quick connect plugs and wire because damn if the retail aren't proud of what they have! Thanks dude!

 

[Ned Kelly]

Alittle off tangent, but you guys sound alternator savvy, .....where's the best place to get a 140amp'er?

 

[lectric80]

There are plenty of places, and even a couple of stock ones that can be used. I don't remember the year, do a quick search, but I believe it is a Pontiac mini-van that had 140 amps stock. And it was almost a direct bolt in. You can also have any of ours upgraded by a competent automotive electrical shop. I have a friend who does this type of work, and he is going to do mine when I am ready.

 

[dremu]

There are plenty of places, and even a couple of stock ones that can be used. I don't remember the year, do a quick search, but I believe it is a Pontiac mini-van that had 140 amps stock. And it was almost a direct bolt in. You can also have any of ours upgraded by a competent automotive electrical shop. I have a friend who does this type of work, and he is going to do mine when I am ready.

Pontiac Trans-sport -- the ones with rear air came with a 140A factory. They are a larger case, but on my '74 small-block it was a bolt-in mount. I did have to solder a little wiring harness adaptor, no big deal.

On my '74 *big block*, however, the factory upper bracket did NOT fit and I had to weld up a new one.

I gather some folks have had issue with newer motors, don't know about that personally.

You can also get Caddy alternators in the same case as ours off-the-shelf in a 90-100A rating.

Note that alternator ratings are a bit tricky; they are maximum output at generally a high RPM, and many specially-wound-for-high-output units actually put out LESS at idle than a stock style unit. This means you may need to race your engine when winching (requires a lot of hands, or a hand throttle) and/or may get a dead battery if you do a lot of in-town driving at night

Lots of threads on this; search on the whole Delco 10SI versus ... what's the other, 12SI?

-- A

 

[teknoslacker]

I used to work at an alternator shop for several years. We used to get guys coming in all the time with super high power CB systems. THey would run several batteries and use Leece-Neville alternators. They put out 165-185+ amps. They seemed to be easy to mount up on SBC and BBC motors. These alternators were most frequently on Ambulances and other larger emergency vehicles.

 

[6.2Blazer]

I believe the "large case" style 140 amp alternators mentioned on vans and stuff are the CS144. Definitely would have to recommend upgrading to this style alternator vs. trying to soup-up a factory 12SI style. As somebody else already mentioned, the ratings are often the maximum the alternator can put out at high rpm's. However in general, something like a CS144 will put out much more amperage at lower rpm's (where the engine is at most of the time) than a hot-rodded 12SI style even if both have the same amp rating.

 

[BKinzey]

Here's another vote for the CS 144. If you Google it you can find lots of info on it, it's variations, where to get one and how to install it

 

[Copasetic]

Awesome info guys, thanks!!