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Calculating amperage draw.....anyone?

Discussion in 'Commercial Snow Removal' started by 440trk, Dec 5, 2007.

  1. 440trk

    440trk Senior Member
    Messages: 112

    Hi Folks,
    I'm looking for advice on how to figure out the electrical requirements for my truck's alternator. I would then use this information to upgrade my current 75amp alternator to one of a more adequate size.

    Truck is an old 77 PowerWagon (hence only a 75 amp alt). I'm probably going to upgrade to a newer 100 amp model....but I want to make sure I'm covered for all my accessories.

    Basically I'm running everything in stock form (headlights, heater, etc...) with the addition of a Meyer E-47 pump, and a 55w dual rotator beacon. So far, I haven't killed my electrical system, but I really need to upgrade. I'd like to figure out what my actual needs are, and then I can figure out additional accessories, and find an alternator to suit my needs.

    Any help, tops, tricks, etc would be greatly appreciated.
  2. PowerWagon

    PowerWagon Senior Member
    Messages: 188

    Hi! I have the same truck power wagon, 74 3/4 ton. Am using the same alt that comes with it never give me a problem, just put in a bigger battery 920cc or 2 batterys, I have just one 920cc it does fine...

    Is your power wagon 1/2 ton or 3/4 ton? Any problems with the front wheel bearings being worn out when plowing??

  3. T-Trim

    T-Trim Senior Member
    from NE OH
    Messages: 207

    You need to find out what your idle output is. So if you alt Can put out 75 amps. But at which rpm range does it put out 75 amps. If you get a Alt with 40amps at idle or 25amps at idle what would you buy?? And when I mean idle amps, I mean amps at which you would receiver to charge and run your goodies. If you need to press the gas down to get brighter light, fast blower motor, or quicker power windows, then check your Alt.
  4. 440trk

    440trk Senior Member
    Messages: 112

    Howdy Steve!

    It's always good to see another old Dodge pushing snow here on the board!

    So far, my system has worked ok. I've noticed that my alt seems to be charging a LOT. If I run the dual rotator all the time, the alt never seems to quit charging. I have a new Mopar 100 amp (older police car style) to swap in...but I want to redo my Amp guage wiring first. I guess I just want to make sure I've safely covered. So far, however, the electrical system has held up over the years. Earlier this year, I put a new 1100cca battery in....and I'm in the process of upgrading/replacing all my battery/plow cables (hey, they've been there since 77...they GOTTA be due for replacment!). I'm sure that will help a bunch as well.

    My Powewagon is a 77 1/2 ton Club Cab, 8ft bed, 400, 2v, auto., 3.55 gear, 31x10.5x15's.
    So far, no problem with the front full-time hub bearings. I keep them well greased, which seem to be the trick to keeping them alive and well. It's amazing how many folks never greased the full time hubs, because they didn't know how/where to do so. I've seen some ugly ones over the years....but so far, my 77 bearings are doing great.

    Glad to hear your electrical system has held up to the same abuse. That makes me feel a little bit better about not fry'ing anything yet...lol.

  5. 440trk

    440trk Senior Member
    Messages: 112

    Hi tom,
    Yea, I'm aware of the different rates of charging....that's why I'd like to figure out what my "required" current draw will be, so I can make sure my new alt. will cover it.

    The 100 amp alt I'm looking to swap in, is the same one that Mopar has used in their police cars in the 70's-80's. They put out fairly well at idle/low rpms..but I still need to make sure they put out ENOUGH for what I want.

    Power windows? In a 77 Dodge plow truck? Nah.... Such creature comforts were quite uncommon in a truck back then.

    I've got wipers, heater, basic lights, plow lights plow pump, dual rotator, and a trailer brake setup. No other electrical draw. I rarely even listen to the radio when I plow....

  6. murphyslaw

    murphyslaw Senior Member
    Messages: 443

    if its doing fine now with the stock alt, then with a bigger one it will do better right? I have the 100amp alt in my 85 w250 and I run a twin 55watt rotor three led strobes headlights added rear light and added front lights, and two batts. and dont have any problems.

    this is the same set up I had in my 78 powerwagon, no problems then either.
  7. 440trk

    440trk Senior Member
    Messages: 112

    Well, I only assume it's doing fine in it's stock form....lol. I know if I run the beacon and do a lot of slow moving plowing, the alt guage stays firmly in the "charging" sector. It hasn't caused a problem...yet.

    Your 85 (if stock) has the same 100 amp alt I'm planning on putting in mine. If you're getting away with THAT much power draw with the 100 amp....than I shouldn't have ANY problems with my setup. :drinkup:

    Very cool!

  8. murphyslaw

    murphyslaw Senior Member
    Messages: 443

    you need to ditch the amp guage its a weak link in your system. I bypassed mine. and get a volt guage, that will tell you better what your state of charge is and bettery condition.
  9. mud

    mud Senior Member
    Messages: 125

  10. 440trk

    440trk Senior Member
    Messages: 112

    Mud....that is EXACTLY what I was looking for!!! Thank you!

    Murphyslaw....have no fear, I'm well aware of the AMP bypass trick, and it will be occuring as soon as I get time to mess with it. I a;ready have the fuseable links for the dash side of the swap....just need time to actually do the deed. :drinkup:

    Thanks guys!!!