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  • Problems with battery

    Hey guys - wasn't too sure what forum to post this in, so i figured this would be best.

    Since i installed my carPC, I have been having problems with my battery. If i drive somewhere, turn off the car, then start it again a few hours later, everything is fine and dandy. If i don't touch my car for a few days, or sometimes even overnight or whatever, it really struggles starting. The other day i even had to get a jump.

    So the first thing that comes to mind is that my PC is draining my battery too much when it's off. I don't keep it on standby or even hibernate it (troubles with lilliput drivers...or something - that's a whole 'nother topic though) - the PC is completely off when not being used.

    Well, what i did was install a switch in the power line for the PC (the wire runs under the carpet right by my feet - no big deal) aaaaaand still have the same problem when i completely cut power to the computer. So I was wondering if this is an actual problem with my battery, or perhaps my alternator? It wouldn't seem like the alternator, cause it starts fine right after being driven. Thanks for the help!

    Power Supply: M2-ATX HV
    Battery: some basic aftermarket Energizer something-or-other. Had it put in a couple years ago

  • #2
    So just debug it. Chuck an ammeter in one of the supply lines from the battery, and start disconnecting stuff until the current drops to an acceptable level. Whatever you just disconnected is the culprit.
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

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    • #3
      Rob's advice is good. You may also try going to a parts store for a free charging system diagnostic test.

      This should tell you if the car is showing an issue not related to the car pc.

      They will tell you if the three parts of the charging system (battery, alternator, and voltage regulator) are healthy.
      TruckinMP3
      D201GLY2, DC-DC power, 3.5 inch SATA

      Yes, you should search... and Yes, It has been covered before!

      Read the FAQ!

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      • #4
        Could your wiring be shorting somewhere?

        Ammeter is a good place to start but you could blow it's internal fuse- some use 600ma, 2amp or 10amp.
        Just be aware of this before you start.

        If you do not have a meter an dc clamp meter will measure very high current ( 400 amps ) as well as the small stuff.

        I've used mine to measure a 600 ma 'inverter in standby' load as well as a short in my buddies motorized seat which drew 83 amps.

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        • #5
          first thing how old is your battery?

          2nd, i had the same issue , the pc still draws power, mine was about 0.3A when off.. not alot you say.. thats still the same as a small interior light.
          I did the switch on the + power wire trick too, untill i build my relay system.
          I also wired the screen after that switch too, so when it is off, everything to do with the car pc is off.

          the amp is turned on by my head unit which is powered off the acc, so im not worried about that.

          that solved my issue, and my battery is getting tired too. it will need replacing within 6 months

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          • #6
            Originally posted by Woofnstuff View Post
            first thing how old is your battery?
            I think it's about a couple years old.

            I think i'll try an ammeter - i guess i didn't realize they had DC clamp meters out there. Should i just measure straight from the + terminal?

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            • #7
              Originally posted by Woofnstuff View Post
              2nd, i had the same issue , the pc still draws power, mine was about 0.3A when off.. not alot you say.. thats still the same as a small interior light.
              !!!!!!!!! Holy crap, do they draw that much? I was worried when mine drew about 0.03 A, I redesigned it to draw 0.007A, I thought that was still a bit much, but I lived with it. Most of that was to flash an LED once every two seconds.

              0.3A...! What the hell is it powering when "off"?
              Old Systems retired due to new car
              New system at design/prototype stage on BeagleBoard.

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              • #8
                Originally posted by Meltz014 View Post
                I think it's about a couple years old.

                I think i'll try an ammeter - i guess i didn't realize they had DC clamp meters out there.
                Sounds like a good start.
                If you are interested in a DC clamp, I use a Craftsman Mfr. model# 82369 $59.99. The only problem is it doesn't have a peak hold feature.

                Originally posted by Meltz014 View Post
                Should i just measure straight from the + terminal?
                Here is how I would test it
                -Disconnect the ground wire negative terminal from the battery.
                -Connect the negative terminal from your ammeter to the ground wire.
                -Touch the positive ammeter terminal to the negative post on the battery.

                You could turn on your hazard lights before starting to have a test current.
                It is safer to measure from the negative since the entire engine, frame, etc will be at the same potential as your meter.

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                • #9
                  the psu still gives power to the pc, off is only a soft off really..
                  im building a relay thingee to sort that out

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                  • #10
                    Well with a M2, why dont you just set the jumpers so that it does a Hard Off after a preset time? Then there wont be any power draw at all.

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                    • #11
                      true if your PSU supports proper shut down stuff, defiantly use that.

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