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Thread: Doesn't hold standby power if I crank the car right away

  1. #1
    Jesus Freak antimatter's Avatar
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    Doesn't hold standby power if I crank the car right away

    This is an odd one and I can't seem to get to the bottom of it and am hoping someone can help. If I get in the car in the morning and immediately crank the the engine, every time it momentarily drop the standby voltage and the computer will come up from a reboot.

    If I turn the aux on and wait for 4 seconds and then crank the engine it will come out of standby almost every time. I have changed my habits to accommodate this by putting my seatbelt on first then crank the engine but there obviously is some underling issue with he m4 ATX.

    Now I have checked the settings of this thing and even lowered the minimum voltage to hold standby current to like 8 volts.

    has any one ran into this issue before or seen anything like this? Does anyone have any suggestions.
    -Jesus- King of Kings Lord of Lords

  2. #2
    Maximum Bitrate kegobeer's Avatar
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    Are you connected to the accessory line or the ignition line?
    1999 Mercury Grand Marquis GS with: ASRock E350M1 w/4GB RAM, 80GB Intel SSD, Opus DCX3.120, Visteon HD Radio + HDR-USB, PL-18N wifi, OBDLink Scan Tool, BTA6210 BT, BU-353, Win 7 Ultimate, CF 4.0, Alpine MRP-F240 + MRP-T220, RF Punch 1572s, Kicker 8" Comp.

  3. #3
    Maximum Bitrate Mickz's Avatar
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    Assuming that the 12v input to the PSU is not dropped as you do this, then if you are running any USB cables over some distance then I would also be looking at some kind of ground loop causing a noise spike to be introduced into the +5v standby rail from one of the USB cable runs.

    Also some supplies can do silly things when the control line is switched in rapid succession, the M4, in my case, will drop its +5 standby line if the "M4 IGN control line" is cycled or pulsed just as the PSU starts. This can happen in a lot of vehicles as they are started.

    My system is powered from a separate (isolated) battery and the M4-ATX would occasionally cause this behaviour.
    Last edited by Mickz; 05-07-2011 at 08:55 PM.
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  4. #4
    Raw Wave
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    You turn to aux for 4 secs. Is that Acc?
    Does Ign for 4 secs work too?

  5. #5
    Jesus Freak antimatter's Avatar
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    Actually I turn Ignition (two clicks) for 4 seconds. i haven't tried just the ACC however on the way home i will try this. I will have to double check if i am connected to ACC of IGN. I think i am connected to ACC.

    I also i have an Isolator and a tank battery (12ah Sealed Lead Acid). Question... should i put a Diode on the 12v switched to this PSU? Maybe a capacitor to smooth out any spikes? Maybe switching to IGN instead of ACC. I am open to anything at this point to correct this behavior

    Sorry i dropped this thread, i didn't get any notifications for some reason.

    ---------- Post added at 04:44 PM ---------- Previous post was at 04:42 PM ----------

    Quote Originally Posted by Mickz View Post
    Assuming that the 12v input to the PSU is not dropped as you do this, then if you are running any USB cables over some distance then I would also be looking at some kind of ground loop causing a noise spike to be introduced into the +5v standby rail from one of the USB cable runs.

    Also some supplies can do silly things when the control line is switched in rapid succession, the M4, in my case, will drop its +5 standby line if the "M4 IGN control line" is cycled or pulsed just as the PSU starts. This can happen in a lot of vehicles as they are started.

    My system is powered from a separate (isolated) battery and the M4-ATX would occasionally cause this behaviour.
    This sounds like exactly the behaviour that i am experiencing. Whats the fix? firmware? i think i am running the latest
    -Jesus- King of Kings Lord of Lords

  6. #6
    Raw Wave
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    The Acc drops out when STARTing so IGN may be better (if the drop causes the behaviour).

    But with a tank battery and isolator it should be okay unless that battery is bad or flat, or the isolator is not voltage or charge-light controlled.


    PS - if stalled and restarting, then a voltage controlled isolator may cause the dropout if it does not release (isolate) before cranking. That behavior varies with each brand, model etc.
    Last edited by OldSpark; 05-10-2011 at 01:43 AM. Reason: PS...

  7. #7
    Jesus Freak antimatter's Avatar
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    So ACC does turn the computer on so i may want to change that to IGN.

    The following is a link to the actual isolator that i have. This one i believe is voltage controlled. I don't know what "charge light controlled" means
    http://www.powerstream.com/battery-i...olid-state.htm

    I just replaced the battery a month or so ago so the battery shouldn't be bad although it is possible that it would go flat after being in standby for several days. But the thing is that it is pretty much 100% repeatable. If i forget to wait 4 seconds it does a reboot. I did some testing a while back and i did notice a voltage drop across the Tank battery during crank. This seemed wrong since it is supposed to isolate during crank

    It seems that it if it is an issue with the ACC line switching off during crank then a properly sized capacitor should smooth things out.
    -Jesus- King of Kings Lord of Lords

  8. #8
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    Charge Light controlled is the UIBI. It's an almost free battery isolator if your vehicle has a charge lamp - all you pay for is the relay (plus the usual inter-cabling and fusing/protection at each battery). It does away with the complications if voltage controlled isolators (eg, the "decision time" referred to in your isolator's literature) and it never tries to con people with lines like "it allows charging of the auxiliary battery only when the main battery is fully recharged" (That bullsh always amuses me! )


    If your isolator's decision time also applies to voltage dips, then it won't necessarily isolate whilst cranking.
    Most similar isolators have the turn-on delay or decision time - eg, 15 seconds etc - after the voltage goes high enough (that's what some call their ha ha bluddy ha (intelligent) priority charging LOL!), but some instead or also have the turn-off aka isolate delay.

    And yours uses MOSFETs. It is unclear if it allows current sharing between the 2 batteries, though I suspect not.
    (I may have missed the pertinent info - I didn't analyse the material thoroughly.)


    But your 2nd battery should not be dying - unless you have no low-voltage cutout to prevent excessive discharge.
    Battery age and condition have little to do with each other. A 10-year battery will fail in weeks if not used appropriately.

  9. #9
    Jesus Freak antimatter's Avatar
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    Assuming that the issue is with the behaviour of the M4-ATX during crank, what can i do to work around the issue besides a firmware fix
    -Jesus- King of Kings Lord of Lords

  10. #10
    Jesus Freak antimatter's Avatar
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    So I bit the bullet and went searching for the IGN wire to hook up too instead of the ACC. I found it and got it hooked up. I haven't thoroughly tested it but the few shutdown cycles that I did run through seemed to be an improvement.

    I think I have a couple issues here. The first is obviously problems with the PSU. The second may be the drain on my aux battery is too much for my rabbits to support the standby current.
    -Jesus- King of Kings Lord of Lords

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