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Re: Battery discharging

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  • Bob Micheletti
    You sparked (pun intended...sorry) my curiosity so I looked at the numbers. My test light (Snap-On) pulls 200ma to fully light. The batteries we are using
    Message 1 of 10 , Dec 1, 2008
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      You sparked (pun intended...sorry) my curiosity so I looked at the
      numbers. My test light (Snap-On) pulls 200ma to fully light. The
      batteries we are using are ~10Ah rated. This means that using my
      method if the test lamp lights fully, the load is enough to
      completely discharge your battery in 50 hours. I could test it but
      I am sure that it would light at less than 100ma, which would relate
      to about a 4-day discharge. Although I agree that a meter with
      ranges from 10A to a few milliamps is more accurate, a test lamp
      will give enough information in most situations to find the
      problem. I suggested it because it is easy to use and nearly
      imposable to damage. Many more tool boxes and road kits contain a
      test light than do a multimeter. If you are going to use a
      multimeter I would like to warn you about a "gotcha". If you
      connect your multimeter to the battery + and - with the test leads
      plugged into the amp jack you will blow the protection fuse if the
      meter has one or worse you will blow the meter if it is an
      inexpensive one without a fuse. Most meters have a separate jack
      for 10A and milliamp because they are fused separately. You can
      also blow the milliamp fuse if your load is more than 2 amps
      (usually milliamp scale goes to 1999ma or 1.999A). Always start
      with the 10A scale and work down and again never connect a meter
      directly to a battery in amp mode.

      Bob Micheletti
      01 Trophy !!!S
      --- In TriumphTrophy@yahoogroups.com, "cpallenjr" <cpallenjr@...>
      wrote:
      >
      > Caution, this might work but if your battery is taking several
      days
      > to discharge it's unlikely that there will be enough current flow
      > through the fault to light a test light.
      >
      > An ammmeter function (one that reads milli or even micro amps) is
      > really the way to go with this. A multimeter is a valuable tool to
      > have in your kit if you take the time to learn how to use it.
      >
      > Courtney in Seattle
      >
      >
      > --- In TriumphTrophy@yahoogroups.com, "Bob Micheletti" <bobmic@>
      > wrote:
      > >
      > > In line with Philip's method, I use a test light.
    • cpallenjr
      Hi Bob, I agree with just about everything in your post except your assumptions about the discharge current flow - I think that a 100mA drain (about a watt at
      Message 2 of 10 , Dec 2, 2008
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        Hi Bob,

        I agree with just about everything in your post except your
        assumptions about the discharge current flow - I think that a 100mA
        drain (about a watt at 12v) would take the m/c battery down to below
        a minimum functional level in a short time still and not light the
        lamp simply because of ohm's law. If your lamp pulls 200 ma at 12 v
        then the resistance is approx 60 ohms. If the fault (short) on the
        bike was drawing 100 ma then the effective series resistance would be
        180 ohms and the theoretical current draw on the circuit would drop
        to about 67 ma.

        A test light is good for measuring the presence of voltage, but not
        necessarily current. An Ammeter is a tool that you need to know what
        you are doing your chances of damaging something is pretty high.

        Courtney in Seattle


        --- In TriumphTrophy@yahoogroups.com, "Bob Micheletti" <bobmic@...>
        wrote:
        >
        > You sparked (pun intended...sorry) my curiosity so I looked at the
        > numbers. My test light (Snap-On) pulls 200ma to fully light. The
        > batteries we are using are ~10Ah rated. This means that using my
        > method if the test lamp lights fully, the load is enough to
        > completely discharge your battery in 50 hours. I could test it but
        > I am sure that it would light at less than 100ma, which would
        relate
        > to about a 4-day discharge. Although I agree that a meter with
        > ranges from 10A to a few milliamps is more accurate, a test lamp
        > will give enough information in most situations to find the
        > problem. I suggested it because it is easy to use and nearly
        > imposable to damage. Many more tool boxes and road kits contain a
        > test light than do a multimeter. If you are going to use a
        > multimeter I would like to warn you about a "gotcha". If you
        > connect your multimeter to the battery + and - with the test leads
        > plugged into the amp jack you will blow the protection fuse if the
        > meter has one or worse you will blow the meter if it is an
        > inexpensive one without a fuse. Most meters have a separate jack
        > for 10A and milliamp because they are fused separately. You can
        > also blow the milliamp fuse if your load is more than 2 amps
        > (usually milliamp scale goes to 1999ma or 1.999A). Always start
        > with the 10A scale and work down and again never connect a meter
        > directly to a battery in amp mode.
        >
        > Bob Micheletti
        > 01 Trophy !!!S
        > --- In TriumphTrophy@yahoogroups.com, "cpallenjr" <cpallenjr@>
        > wrote:
        > >
        > > Caution, this might work but if your battery is taking several
        > days
        > > to discharge it's unlikely that there will be enough current flow
        > > through the fault to light a test light.
        > >
        > > An ammmeter function (one that reads milli or even micro amps) is
        > > really the way to go with this. A multimeter is a valuable tool
        to
        > > have in your kit if you take the time to learn how to use it.
        > >
        > > Courtney in Seattle
        > >
        > >
        > > --- In TriumphTrophy@yahoogroups.com, "Bob Micheletti" <bobmic@>
        > > wrote:
        > > >
        > > > In line with Philip's method, I use a test light.
        >
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