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  1. 16th March 2009, 09:27 PM #1
    mic-d's Avatar
    mic-d
    mic-d is offline GOLD MEMBER
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    Default rechargeable battery maximum current draw?

    I am trying to find out what is the typical "wattage" rating of high-end cordless drills. I can't find anything like the ratings that are assigned to corded tools for the cordless equivalent so I suspect there is a complex answer to this.
    For example, say I have a 24V cordless with a 3AH Li ion battery, I might be able to run it for 30mins with no load. Does this mean, roughly speaking that it draws 6A at 24V so produces 122W? If I subject it to load and the battery drains in 10mins, has the drill drawn 18A at 24V producing 432W?
    Would it be in the realms of possibility for a cordless to produce this kind of wattage and would the battery survive?

    Cheers
    Michael
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  3. 16th March 2009, 09:36 PM #2
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    yes.

    i dont quite understand what u are on about. but i might be a bit thick.

    www.carlweiss.com.au
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    8" & 10" Lucas Mills, bobcat, 4wd tractor, 12 ton dozer, stihl saws.
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  4. 16th March 2009, 11:33 PM #3
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    Actual current delivery depends on the configuration of the battery pack.

    Current draw also varies with load - a drill spinning under no load sucks less power than the same drill almost stalling as you drive a fastener home.

    Battery makers rate the battery delivery by its C rating - how long it takes the battery to discharge under load. The higher the C rating, the more juice you can suck from the pack.

    See here for more details...
    http://knol.google.com/k/jason-molle...km20m0h0ff0/3#
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  5. 17th March 2009, 06:12 AM #4
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    Thanks, that is exactly what I was after

    Cheers
    Michael
    Quote Originally Posted by Master Splinter View Post
    Actual current delivery depends on the configuration of the battery pack.

    Current draw also varies with load - a drill spinning under no load sucks less power than the same drill almost stalling as you drive a fastener home.

    Battery makers rate the battery delivery by its C rating - how long it takes the battery to discharge under load. The higher the C rating, the more juice you can suck from the pack.

    See here for more details...
    http://knol.google.com/k/jason-molle...km20m0h0ff0/3#
    memento mori
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  6. 17th March 2009, 04:08 PM #5
    just starting
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    Default output current

    The output current also varies with temp, age etc.
    So a cold battery can output more current than a hot battery.

    As for peak output currents that usually depends on internal resistance of the battery in question. Lion batteries for cordless power tools usually have a low internal resistance so the max output current can be very high.
    So a high voltage, high Amp Hour battery may not be that great if the internal resistance is high.
    Last edited by just starting; 17th March 2009 at 04:14 PM. Reason: added a comment about the high internal resistance
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