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Thread: Draining Battery

  1. #31
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    I decided to try the relays. And I am very happy with the results. I tapped into the cables and re-route the positive wire connected to a DPDT 12v miniature relay. Then the 12v of a molex to activate the switch.
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  2. #32
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    With regards to your multimeter, you usually need to move the positive (red) lead to one of the Amp plugs from the Volt/Ohm plug. The negative/ground (black) lead stays in the Common plug for nearly all uses. This may be a no-duh statement, but who hasn't had a brainfart, and I didn't see this scenario mentioned in the thread before.

  3. #33
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    Quote Originally Posted by vanndaddy View Post
    With regards to your multimeter, you usually need to move the positive (red) lead to one of the Amp plugs from the Volt/Ohm plug. The negative/ground (black) lead stays in the Common plug for nearly all uses. This may be a no-duh statement, but who hasn't had a brainfart, and I didn't see this scenario mentioned in the thread before.
    Hah, unfortuantely I wish that were the case. I tried everything I could think of and came to the conclusion that my cheap RadioShack multimeter was toast - as far as current readings go. Voltage still works okay.

    I picked up a Craftsman clamp on DC/AC Multimeter and it seems to be working okay. Now I've got to try different scenarios with the carputer on/asleep/etc and figure out how much current is being drawn. And then from there, depending on the readings, I'll ahve to figure out what component(s) is/are causing the drain. Thanks!

  4. #34
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    My car seems to draw around .2 Amps maximum on it's own with the Mini powered completely off.

    With the ignition switched on (to power the Mini), and then off, I had around a 4.4Amp draw. I switched the Mini to be asleep and it was drawing around 1.3-1.4Amps (subtract around .2 - .3 Amps as I had opened my doors a little while ago). That still seems like way too much. Right? Any idea what the Mini/components should be drawing while asleep?

    As far as USB components, I've got the Lilliput touch screen, BU-353 GPS receiver, VAG-Com, Griffin Powermate, and a USB hub, that is self powered at this point - although I have a CNX-P5V sitting here waiting to be installed.

  5. #35
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    Quote Originally Posted by TTeuer View Post
    My car seems to draw around .2 Amps maximum on it's own with the Mini powered completely off.

    With the ignition switched on (to power the Mini), and then off, I had around a 4.4Amp draw. I switched the Mini to be asleep and it was drawing around 1.3-1.4Amps (subtract around .2 - .3 Amps as I had opened my doors a little while ago). That still seems like way too much. Right? Any idea what the Mini/components should be drawing while asleep?

    As far as USB components, I've got the Lilliput touch screen, BU-353 GPS receiver, VAG-Com, Griffin Powermate, and a USB hub, that is self powered at this point - although I have a CNX-P5V sitting here waiting to be installed.
    That actually doesn't seem too unreasonable considering power supply inefficiency. watts = volts * amps so at 12 volts a 1.3 amp draw is only 15.6 watts. At 1.3 amps, on a 20 amp-hour battery you're going to be able to get 15 hours. Also that type of amp meter is a little inaccurate.

    How many amp hours is your battery actually rated for, 20 was a semi-possible random guess?

    If this is really problematic, you can probably just kill power to everything with a relay when the car is off.
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  6. #36
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    Quote Originally Posted by PaulF View Post
    That actually doesn't seem too unreasonable considering power supply inefficiency. watts = volts * amps so at 12 volts a 1.3 amp draw is only 15.6 watts. At 1.3 amps, on a 20 amp-hour battery you're going to be able to get 15 hours. Also that type of amp meter is a little inaccurate.

    How many amp hours is your battery actually rated for, 20 was a semi-possible random guess?

    If this is really problematic, you can probably just kill power to everything with a relay when the car is off.
    I don't want to have to kill power to everything - everything I've ready has pointed towards the fact that I should be able to leave my Mac Mini asleep for DAYS not a matter of hours. I've read the Mac Mini should take around 3-5 watts asleep.

    I have no idea what my battery is rated for, however.

  7. #37
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    I read the post wrong also. I went back to the first post for reference accidentally.

    Let me just get all your info straight...
    1. With the mac completely powered off you draw .2 amps?
    2. With the mac completely powered off your car battery dies overnight?
    3. With the mac in standby mode it draws 1.3 amps?
    4. With the mac in standby mode it lasts how many hours?
    5. Look at the battery's label. It should say the number of amp hours it is capable of.
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  8. #38
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    Quote Originally Posted by PaulF View Post
    I read the post wrong also. I went back to the first post for reference accidentally.

    Let me just get all your info straight...
    1. With the mac completely powered off you draw .2 amps?
    2. With the mac completely powered off your car battery dies overnight?
    3. With the mac in standby mode it draws 1.3 amps?
    4. With the mac in standby mode it lasts how many hours?
    5. Look at the battery's label. It should say the number of amp hours it is capable of.
    1. With the Mac Mini powered off in the sense that the Carnetix power supply *completely* cuts power, only .15 - .2 amps are drawn by the car itself. I can get this to happen if I let the Carnetix put the Mac Mini to sleep, and then if I wake it up manually, the Carnetix will eventually shut off power completely because it realizes the computer is on, and the ignition switch is not on.

    2. I'm unsure of what the Mac Mini draws when powered off. I haven't been able to get that current reading yet. What I mean, in this instance, is that I manually go the "Apple Menu" and select Power off. I haven't taken a current test like this - but my battery is almost always dead by the next morning, just as if I left the computer asleep.

    3. Correct. 1.3 - 1.4amps.

    4. I'm not really sure the exact amount of hours. Around 12 hours and its dead. If its not dead, my car alawys lets me know that the battery voltage is low.

    5. I did, and it does not say. Only the day I purchased it from Interstate. There's no other information on it.

    Thanks!

  9. #39
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    See I think this is odd because a car battery usually has over 10 amp hours and even with a 5 amp hour battery, a .2 amp load would take 25 hours to drain the battery. I think this is a defective/crappy battery problem.
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  10. #40
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    I replaced the battery in September thinking this was the issue... and I took the replacement battery back to Interstate - they tested my battery (they checked the fluid in each cell) and said it was fine... :/

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