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Thread: Car Battery Tester Measure Amps and Alternator Draw - Measure DC Amps

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    Boyntonstu's Tools

    Car Battery Tester Measure Amps and Alternator Draw - Measure DC Amps

    In order to measure 100 Amps DC I am using a multimeter and a 18.75" length of 0.128" Diameter solid copper wire (#8).

    The voltage drop measured across the wire in mllli-Volts directly equals the current in Amps.

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  2. The Following 2 Users Say Thank You to Boyntonstu For This Useful Post:

    Jon (09-17-2015), kbalch (09-23-2015)

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    Jon
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    Thanks Boyntonstu! I've added your Car Battery Tester to our Diagnostic and Testers categories, as well as to your builder page: Boyntonstu's Homemade Tools. Your receipt:

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    Supporting Member mklotz's Avatar
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    mklotz's Tools
    Can you explain how you calibrate your device? Are you using a low-resistance ohm-meter to measure the resistance of the copper wire or do you have a calibrated current source?
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    Great tip, Boyntonstu! Thanks for posting this.

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    Supporting Member jere's Avatar
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    jere's Tools
    very neat tip! what amperage is the alternator in the vehicle rated at? rather than adding a battery you might consider changing the alternator for one with higher output.


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