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Alternator recomendation on 84 Chevy

Discussion in 'Truck & Equipment Repair' started by BurnoutNova, Feb 22, 2013.

  1. BurnoutNova

    BurnoutNova Junior Member
    Messages: 8

    My 100 amp alternator seems to be on it's way out. I'm thinking about a 140 amp 1 wire alternator, but a little concerned that a 1 wire, even with low speed cut in voltage regulator might not keep up to keep my single battery e47 pump setup powered.

    Last night it was a problem, and the truck was down for a few hours while we jerry rigged another alternator on.

    Anyone have a good recommendation? Maybe part of my problem is only 1 battery, but my local plow shop recommended I go with this setup.
  2. wva

    wva Member
    Messages: 78

    Hey there I run older trucks,and have found that I'm much better off with two batt's I use two 1000cca batt's just connect pos.to pos. and neg. to block I have had no problem with my E60 with that setup For the 2nd batt,I welded a piece of 2'' angle from inner fender to rad. support an put a batt box in it was tight fit for box add 2self drilling screws and your good. I hope this help
  3. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,122

    The number of wires is, by itself, not important. The total amount of copper determines the current that it is able to transfer. You can have one BIG wire, or multiple smaller ones, the results are the same.

    Now here's the deal with plow pumps, batteries, wires, and alternators;

    The plow pump motor will be running off some combination of the BATTERY and the ALTERNATOR. Typically, the alternator output is NOT enough to power both the vehicle AND the plow pump motor, and that fact isn't going to change with a bigger alternator. It will, however, handle a greater PORTION of the plow pump motor's demands.

    Basically, the only important thing for the alternator, is that it is able to provide a power output that exceeds the total AVERAGE vehicle power demands. Since you aren't operating your plow pump motor continually, you don't need to be able to power it continually.

    BUT YOU DO need to be able to provide for its instantaneous power demands!!! This is where the battery comes in. In a time when you are using your plow *frequently*, for example, DURING a job, the battery can't be allowed to run down too far. It needs to have adequate capacity to feed the plow motor AND the vehicle during this period of high demand. If you run the battery down all the way, you'll kill the vehicle's ignition when you activate the plow.

    If your battery isn't up to the task, you can go with a bigger battery, or multiple batteries wired in PARALLEL.

    The wire running from the alternator to the battery needs to be able to transfer the entire output of the alternator without significant voltage drop and without heating up too much. The second part of this to consider, however, is the NEGATIVE side of the circuit. Often overlooked, the negative is transferred through the alternator's body, through the ENGINE, through whatever means the engine is attached to body (often weak), and finally from the body to the battery. The wire-to-body connections often go bad, get worse, etc. If there is any doubt in your mind about the connections from the alternator to the battery, it can never hurt to run two fresh HUGE wires directly from the alternator to the battery. Keep those wires as short as practical to minimize voltage loss.

    Also don't forget the plow to battery connections. If these connections are weak, it can make it appear like the battery or alternator is weak.
  4. wva

    wva Member
    Messages: 78

    forgot to mention that I replaced the batt wire from alt. with at least a #8 stranded wire.
  5. ceptorman

    ceptorman Senior Member
    from Indy
    Messages: 208

    That's a lot of great info jasonv, thanks.
  6. Blizzard1980

    Blizzard1980 Senior Member
    Messages: 187

    x3 on dual batteries.
  7. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    This is where you have to decide what to accept as good info from the Internet as there's some misinformation as well as some misinterpreted info in that post.

    One is obviously he doesn't know what a one wire alternator is...
  8. jb1390

    jb1390 Senior Member
    Messages: 710

    The middle parts are decent, i almost stopped reading after the incorrect interpretation of a one wire alternator. The beginning and end have a bit of incorrect information though.

    Two batteries will never hurt, to the op, how is your ratio of driving to plowing? If your engine has a chance to spin the alternator at elevated speeds between accounts i bet you'll be just fine with a one wire.
  9. GSS LLC

    GSS LLC Senior Member
    Messages: 640

    I run dual batteries and the 100 amp alt on my four 80's Chevy trucks. Works fine.
  10. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Incorrect. The majority of the electron travel is on the surface of the wire strand. That is why conductors for heavy current applications are always stranded, much more surface area on 100 small strands than 1 large strand.

    Jason's knowledge of vehicle electrical systems varies from slightly misguided to grossly innacurate. Proceed with caution.
  11. jb1390

    jb1390 Senior Member
    Messages: 710

    2nd part about proceeding with caution is correct on much of his advice.

    First part, while you are technically partly correct, cross sectional area has more to do with current carrying capability than number of strands, on a low voltage dc system. When you start talking about high frequency signal transmission, then things like characteristic impedance start to matter. But for 12 volt or even 120 volt systems, solid or stranded won't make a detectable difference.
  12. jb1390

    jb1390 Senior Member
    Messages: 710

    Sorry, double post.
  13. Rat_Power_78

    Rat_Power_78 Senior Member
    Messages: 184

    Everyone has thier own opinions when seeking advice on the internet, so be cautious of who you listen to. That being said, the following is what I experienced with a similar truck:

    When I was running my '76 K20 as my main plow truck, I was always plagued with a lack of electrical power and spent far too much time trying different things to solve the issue. One thing to consider: If the alternator you are looking at is rated at 140 Amps, how many RPM is that rating at? Often, it seems high-amp alternators dont put out near what you would think at the low RPMs seen while maneuvering at low speeds. According to a local alternator/starter shop, it is possible to build an alternator that will put out more amps at low RPM than your typical generic "140 amp alternator." If you have a known, trusted shop like this in your area, seek out their advice. I did not find this out until I retired the truck from regular service, so I had a slightly different solution that worked well for me.

    Stock, the truck ran a 10si alternator (charging wire plus the 2-prong factory plug), which put out 63 amps stock. That was the biggest available to me in that case size I changed to a 12si alternator (same wiring setup), rated at 93 amps. the case of it is slightly larger, but I was able to fit it in my application. I dont recall if I had to change a bracket or not. The real beauty of this alternator is every parts house stocks them, making replacements easy and quick to get, and the price was reasonabe-far more so than the aftermarket high-amp units. I had been running dual batteries for many years prior to this, but I wanted to make sure they were getting a good charge. We retained the stock charging wire and added an 8 guage wire from the charging post on the alternator directly to each battery. We also ran an 8 guage wire to the plow solenoid where the positive battery cable connects to it. This setup cured my power issues and I ran it for several years before replacing the truck.

    A note on dual batteries- there was a factory auxilary battery tray made if you dont want to fab your own, not sure if you can still get them from GM or if you would need to find a used one. Be sure to run a ground from battery #2 to the frame instead of to battery #1 as it seems to work better. Finally, and most importantly, be sure to use two new, identical batteries. I learned the expensive way that one new and one used will kill each other very quickly. Same goes for using two different batteries. You may be able to use an isolator to get around this, but I personally would not.
  14. jb1390

    jb1390 Senior Member
    Messages: 710

    Very nice writeup ratpower, wish there was a way to "like" this post
  15. Rat_Power_78

    Rat_Power_78 Senior Member
    Messages: 184

    Thanks. Hopefully it can help someone. Years and years of frustration all condensed to a couple paragraphs...
  16. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    You were doing very well up until you stated this. Never run a primary ground to the frame, always go to the engine or you set yourself up for unnecessary potential problems.
  17. ceptorman

    ceptorman Senior Member
    from Indy
    Messages: 208

    Thanks B&B, after reading your twin battery install I now know what you mean. Does this fall under the old saying..."if you can't dazzle them with brilliance, baffle them with bullish*t"?
  18. Rat_Power_78

    Rat_Power_78 Senior Member
    Messages: 184

    What sort of problems? It seemed to work fine this way, but if its wrong, I would like to know for next time.
  19. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Think about these couple things.

    1) Why doesn't the OEM run the battery (either main or aux) ground cable to the frame?

    2) What are all your heavy current components grounded through? I.e. starter, alternator etc?

    3) On a aux battery install with the battery grounded to the frame, what is completing the ground path on it's way back to those same heavy current components and ultimately, the main battery?

    Remember, ground is one half of the current loop between the supply (battery) and the loads in the electrical system.
  20. Rat_Power_78

    Rat_Power_78 Senior Member
    Messages: 184

    I dont know how I missed this originally. I went back and looked at the truck today, and what I had done when hooking it up goes like this: the ground on my auxilary battery is a 2-guage cable that runs down and bolts to a clean spot on the frame. The part I forgot is there is a second cable that runs from this same spot on the frame up to the block. I think the idea behind this was to ground everything to everything. I was taught that ground issues are the most common cause of automotive electrical problems, and we wanted to eliminate this as a possible issue on that truck. Considering the age of the truck, adding a known good ground from engine to frame seemed to be a good plan. I didnt think it would cause a problem connecting it this way, as it seems to be accomplishing the same task, but then again I could be wrong. Would you typically connect to the block or to the main battery ground post on an install like this?

    I have a lot of respect for you and the amount of knowledge you have on such subjects. Besides, not just anybody can get a smilie named after them. :mechanic: