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KC Lights pull to much juice

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Monster, Mar 21, 2003.

  1. Monster

    Monster Registered Member

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    I just installed 4 KC Daylighters on my K5. These lights are extremly bright but I have one problem. After a couple of minutes or so my voltage gauge slowly drops to 11 volts and lights become a little dim. My alternator is the stock 80 amp and I only have single battery. Should I get a bigger alternator if so how many amps. Also Whats the deal with dual batterys?? Is is good to have two batterys?? Can some one explain step by step how to setup two batterys?

    /forums/images/graemlins/grin.gifThanks for the info /forums/images/graemlins/grin.gif

    <font color="blue"> 86-K5,10-bolts,4.56 gears,Hotted 700-R4,6"lift,35BFG,300Hp,Empty Wallet /forums/images/graemlins/cool.gif</font>
     
  2. GMCLegacy

    GMCLegacy 1/2 ton status

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    it would not be benefical for you to add another battery if you were to keep the same alternator. the lights would still get dim, just not as soon. so you are going to either have to buy a larger alternator or add another one. i have always thought of having 2 batteries and 2 alternators in independent circuits. the stock alternator would still power the same stock battery setup, and add another setup for your KC's. if you are running 4 of the 150W daylighters, that would be a 50 amp draw. so you could easiely get another stock 80 amp alternator and battery to power those lights. and if you keep 2 of the same alternators it is nice to know you will always have a backup if the stock loacted alternator that is powering your ignition goes out on the trail.
     
  3. fredekr

    fredekr Registered Member

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    Hmm... sounds like you may need a bigger alternator, or maybe one that is really putting out 80 amps? How much amperage are your lights drawing? Here's some food for thought/intro electronics:

    1. amps x volts = watts
    Pretty much everything you'll deal in a vehicle with is nominally 12V. For example if you've got 4x150W lights you've got 600/12 = 50 amps drawn by your lights.

    2. Think of electricity like water. The battery is a tank. The alternator is, uh, a well pump that puts water back in the tank. Your lights are pipes out of the tank. Turn the lights on, you open the pipes. Tank starts draining out. Tank will soon run dry (low voltage = your battery is low) if your alternator (aka pump) can't keep up. If you get a bigger tank (two batteries), it'll last a little longer, but your $$ is obviously much better spent on getting a better alternator (higher capacity pump).

    3. Alternators are rated at a given RPM (alternator RPM, that is, not engine RPM). It's usually not idle. Output also drops off when the alternator gets hot. Wrangler Power makes good, expensive alternators; you get what you pay for most of the time. I've never had reason to have a bigger alternator so I can't speak from experience. /forums/images/graemlins/ignore.gif

    4. So what good are 2 batteries? Two or more batteries applications where you'll need to draw a bunch of power -- either in a hurry (winch) or over a long time (running appliances in a camper) and you'll be able to recharge before the battery gets too low. This means that you've got to stop the power draw and recharge -- like you're done winching and you let the alt recharge the battery, or you're done camping and you drive away. Two batteries have other advantage too, of course (backup starting, etc). Note that different batteries are good for different things: long, small draw is called deep cycle, high, very fast draw are starting batteries. This is why a starting battery can crank an engine (lots of amps) but can die if you leave the dome light on overnight (only a few amps, but over a long time). /forums/images/graemlins/blush.gif

    So back to your post -- besides your lights (better alternator), what do you plan to do with your electricity? /forums/images/graemlins/thumb.gif

    cheers!
    Kevin
     
  4. fredekr

    fredekr Registered Member

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    [ QUOTE ]
    i have always thought of having 2 batteries and 2 alternators in independent circuits.

    [/ QUOTE ]

    That's an interesting thought... never heard of that before, but I like it! You could definitely get 2 cheap alternators for the price of 1 good big one. /forums/images/graemlins/deal.gif If you didn't isolate the circuits the regulators might get confused... /forums/images/graemlins/confused.gif ...interesting...

    cheers,
    Kevin
     
  5. Z3PR

    Z3PR Banned

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    Befor you go spending your hard earnd money on a Hi-amp alternator from a parts store or mail order, look into local rebuild shops. I used to rebuild starters and alternators for a living. Most shops can put together a hi-amp unit for you at half the price of one at the parts store.
     
  6. BowtieGuy3

    BowtieGuy3 Guest

    This kinda sounds like the other discussion we had on the Powermaster topic. I got a reply on there that could be of some use to you.
    Powermaster Alt. posting
     
  7. Sandman

    Sandman 3/4 ton status Author

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    Sounds like your alternator is bad. Each 100 Watt KC light will pull around 8 ish amps. So all four would be around 32 amps. You alternator should handle that with no problem.
     
  8. BrianDamage

    BrianDamage 1/2 ton status

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    I got a 90A alternator form NAPA last week...works really good. I had a problem with voltage drops (especially when using power windows) - voltometer reads approx. 14V. with almost no drop now. It cost about $70 I think
     
  9. bablazer73

    bablazer73 1/2 ton status

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    I had the same problem. I used a 160 amp alternater from a GM C60-C70 series truck. It's a little taller, but width wise, it fit the stock brackets. I had to elongate the hole on the upper bracket that goes to the water pump, and put a 1/4 spacer under the bracket that bolts to the intake, But my stock wiring fit. Best of all, I got it for 100.00 from my local rebuilder!! cheaper than a stock sized 110 amp from napa!! If I had a digital camera, I'de show you how well it fit!!
     

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