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How many Amps to start a V-8?

Discussion in 'The Garage' started by BigBen, Mar 21, 2006.

  1. BigBen

    BigBen 1/2 ton status Premium Member

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    I know that the easy answer is to say "MORE is better":laugh: .... but I want a "reasonable" limit on cost.

    I want to pick up a charger that can also "jump" my truck if it's dead in the morning.:crazy:

    They sell chargers for anywhere from 50 to 250 amps of 'starting' current.
    Obviously the price is higher for more amps.

    So.... does anyone have some insight as to how much current I'll need to jump start a V-8 in the morning if I ever need it?

    Thanks guys,

    -Ben

    PS:
    Engine in question is a stock 350 TBI in '95 Yukon.
    Second engine is Carb'd 383 in the K5.
     
  2. dhcomp

    dhcomp 3/4 ton status Premium Member

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    Depends on a lot of things, mainly the starter.

    But think about this. 250 starting amps.......vs. the cold cranking amps rating on your battery. Mine is somewhere near 6 or 700cca.

    Thats a big difference. Doubt that little charger will start it.

    Just keep a spare battery around that is charged, and jump it off of that. That way you can keep it charged with a cheaper (less "starting" amps) charger.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Only thing I've ever seen in print, and it was not specifically Chev data, was that a starter draws something like 300-400amps.

    I could probably dig up the data if I need to. Kind of like stock fan CFM, the info has to be out there, but it's very hard, if not impossible, to find.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    A 50 amp charger will do the job, but you'll have to wait a couple of minutes. I have a 2/10/50 and it can only put out 50 amps for about 1 minute, then it shuts down to prevent overheating. But it will usually start a stock 350 with a dead battery when it kicks back on a minute or two later. The battery holds the charge and builds up as the charger is charging.

    The 250 amp models will start pretty much any stock engine almost instantly. A GOOD starter will only draw 100-125 amps on a stock engine on a fairly warm day. The current draw increases as the weather gets colder and the oil in the engine thickens up. Starter motors can draw well into the 400-450 amp range when worked exceptionally hard, like when the engine is siezed. ;)
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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  6. BigBen

    BigBen 1/2 ton status Premium Member

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    Thanks for all the help so far guys.

    So, does the charger only have to "add to" the lowered battery amperage?

    I'm glad to know that the 700 cca is well above the normal draw of a starter.
     
  7. dhcomp

    dhcomp 3/4 ton status Premium Member

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    I wasn't suggesting that you needed 700cca, just that 250 sounded low by common sense. I guess my common sense failed me :)

    sorry
     
  8. HarryH3

    HarryH3 1 ton status Author

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    Yes. If the battery is totally flat, then it will just take a little longer to get a charge in it with the smaller charger.
     
  9. 3 on the tree

    3 on the tree 1/2 ton status

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    My charger has a 150 amp start circuit . It'll roll over a 460 in -20 weather, just have to let it boost the battery for a minute before hitting the key.
    The charger is a Schumacher,bout 6 years old. You can still get them for less than 100 bucks. It has 2 amp setting for slow charges, and 15 amp setting for faster charges. Buy a name brand charger, so it will last more than 1 year.
     
  10. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    A standard chevy starter turning a 8.5:1 compression chevy 350 draws about 350-400amps at ~12VDC at room temperature. At -20, it's a lot more (don't remember the % vs temp drop), IIRC it's something like 500-600amps.
    More compression, more amps needed to turn it.

    That being said, you don't need a 400amp charger to start your engine. As other's have said, let the dead battery store some of that energy for a little bit before attempting to start. Even just a couple of minutes is usally enough to start, if you have a good running engine. The longer you have to crank for it to start, the longer you'll need to leave your charger on.
     
  11. diesel4me

    diesel4me 1 ton status Premium Member

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    OEM specs...

    In my owners manual for the 79 C10 it says a 350 amp battery is reccomended for a stock 305 or 350 V8 truck..of course this does not take into consideration any accessories like winches,lights,etc..I was suprised they considered that sufficient really..

    I try to "over buy" a battery,I get the 500+ cranking amp versions,and not the cheapest 30 dollar ones that have the bare minimum of plates and lead in them..pick up 2 batteries at a store and compare the weight of the 30 dollar one VS the 40 or 50 dollar ones,and then look at the amp ratings..

    Two ratings of concern are "Cold Cranking Amps",and "Reserve Capacity"...some have great CCA ratings,but only for a short duration,and have limited "reserve"...others have lower CCA,but longer reserve capacity (usually deep cycle batteries fit in this category)...

    I was considering buying one of those "jump start" power packs,but decided I might just as well buy a good battery for the same price..if you do buy one,dont get the 300 amp china ones,at least 900 amp ones are the only ones worth buying..:crazy:
     
  12. gravdigr

    gravdigr 1/2 ton status

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    A charger to jump a truck in the copld is fins as long as you have some place to plug it in. Where I have to park our trucks there is no power handy. I prefer to use a jumper pack. I just have one of the cheap $50 jobs and have been using it for 3 years now with no problems. I have used it to jump motors ranging from the 305 in my blazer to the 351 and 400s in our cemetery trucks. I even helped turn over our diesel backhoe in the winter when it was so cold the diesel was gelled (had to add kero to the fuel cans). A regular battery will also do the job but the jumper pack has the advantage of always being charged due to being plugged in when not in use, it is easily portable with battery clamps built in so no need to dig out jumper cables, And it can be taken along in the truck and charged through the cigarette lighter. And often they come with a light, accessory power port, and a mediocre at best air pump.

    definitely something to consider.
     
  13. BigBen

    BigBen 1/2 ton status Premium Member

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    Thanks all.

    I think I'm educated enough now to go look at chargers and jump packs this weekend.
     

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