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Question. Battery.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by blueberries, Apr 10, 2016.

  1. blueberries

    blueberries New Member

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    I would like to learn how to figure mAh for my modules. I made a load tester (with a headlight and voltmeter). My first cell measured 7.68V initially and 7.34V under a "lite" load. Is there a formula? Could you please provide an example? I purchased a Supermate and want to charge/discharge/balance some modules. Thank you in advance.
     
    #1 blueberries, Apr 10, 2016
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    An Ampere-hour is the flow of 1A of current for one hour, hence mAh is milliAmpere-hours where a milliAmp is 1/1000 of an Ampere.

    When you are determining this for a battery, one practical issue is that the flow of current tends to diminish over time as the battery voltage drops, assuming you are using a fixed resistance load: Ohm's Law: Voltage = Current x Resistance

    So you would have to decide whether the voltage drop over time is linear, or follows some other curve, to determine the average voltage over the period of time that you are testing.

    Once you have the average voltage and you know the resistance, you can determine the average current flow over the time period.

    Also, recognize that the Ah capacity of a battery depends significantly on how much current load is applied. If you use a very high resistance which results in a low current flow, then the Ah capacity will be much higher vs. using a low resistance and high current flow. Typically Ah capacity is cited in terms of the current flow used during the test.
     
    #2 Patrick Wong, Apr 10, 2016
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  3. blueberries

    blueberries New Member

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    Ok, don't hate me but is there a how to load test, evaluate, charge, discharge, balance your modules for dummies step-by-step list somewhere? I still don't understand how to do it but thank you for responding. I know from reading all the threads that you are a pretty cool dude!
     
    #3 blueberries, Apr 10, 2016
  4. exstudent

    exstudent Senior Member

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    #4 exstudent, Apr 11, 2016
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  5. blueberries

    blueberries New Member

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    #5 blueberries, Apr 13, 2016
  6. ericbecky

    ericbecky Hybrid Battery Hero

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    #6 ericbecky, Apr 13, 2016
    Last edited: Apr 13, 2016
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