Batteries drain in 4 hours

Discussion in 'Trucks [ Eighteen Wheelers ]' started by 5thgear, May 4, 2014.

  1. 5thgear

    5thgear Bobtail Member

    Dec 7, 2013
    I can't figure this out and my companies shop is no help. I figured I'd ask you guys and see if maybe someone wiser can help.

    The setup:
    Drive all day, so my batteries are definitely charged. Stop truck for my 10 hour break. Go to bed with the truck turned off. My truck in equipped with a Cobra 1500 watt inverter with my phone charger, and 1.7 cubic ft dorm fridge, and my microwave plugged in. Obviously the microwave isn't drawing much of anything and the fridge only pulls 150 watts continuously.

    The Problem:
    About 4 hours after the truck was turned off THE INVERTER will sound a low voltage alarm. I get up thinking its the trucks load shed. The trucks voltage gauge reads 10 - 11 volts sometimes, 13 other times. The truck starts just fine.

    I had the batteries tested at a petro last night. All 4 putting out 13+ volts and 725+ CCA. I've had the mini fridge in the truck for over a month, but this started happening about a week ago. I have also recently seen the volt gauge read 12.5 - 13 once the truck is started and then shoot up to 14 after a few seconds.

    I don't know where to start as far as finding the problem. But this is killing my idle time. Does anyone have any ideas that could help me find the culprit?

    Edit: The truck is a 2012 International Prostar with the Maxxforce engine
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  3. allan5oh

    allan5oh Road Train Member

    Jan 6, 2010
    Winnipeg, mb
    1) You're assuming the batteries are actually getting a charge

    2) Check voltage BEFORE starting, leave key on

    3) See if this voltage matches the actual voltage at the batteries

    4) At what voltage does the inverter kick off? Can you change it?

    It sounds like there's a wiring issue between the batteries and the truck.
  4. Heavyd

    Heavyd Road Train Member

    Feb 4, 2009
    Batteries tested wrong. No battery should be tested at 13+ volts. Retest with a starting voltage at 12.6V. It does make a difference. The factory batteries seldom last longer than a couple of years before this stuff starts to happen. If the batteries where tested with an electronic battery tester, this has to be done a specific way to get accurate results. Not too many guys hook up the correct or all of the proper connections and batteries get passed or failed by error. Retry with a carbon pile tester type, with a starting voltage of 12.6 with a load of 1/2 the CCA for 15 seconds. If the voltage drops below 9.6, they are junk.
    86scotty Thanks this.
  5. 5thgear

    5thgear Bobtail Member

    Dec 7, 2013
    I'm on a 34 today and I'm deliberately not running the truck. I have my multimeter ready to check the voltage.
    1. I am assuming the batteries are charging mainly because I've taken them to the brink of dead and beyond before. I'm familiar with how the truck starts when its almost gone, and that's not what its doing.
    2. The voltage I stated, 10 - 11and sometimes the normal 13, is key on engine off.
    3. I'm assuming multimeter across each battery will give me the true voltage on each one. Correct me if I'm wrong.
    4. According to cobra its something like 10.8, and it doesn't seem like its adjustable. Not sure I want to go any lower than that anyway. I hate having to call road service for jump starts.

    As for the wiring, that's what I'm leaning towards to. Even before this, this trick had some... Issues. The shop found a loose alternator wire and claimed that as the culprit, but I never bought that as the sole cause.

    And Heavy, unfortunately I don't think my company will pay for another test this soon but if I can sneak one in next PM, I'll refer back to your instructions. Good to have detailed instructions. I always thought it was strange that they could test 4 batteries in an hour when auto zone took about that time for their machine to do one.
  6. RSQ20

    RSQ20 Medium Load Member

    Keep in mind, the battery BANK is just that (a BANK). all the pos are connected together and the neg connected together (Parallel circuit).

    To conduct a proper battery load test, you must disconnect one side of the battery first.... You probably have one with a shorted cell and there fore will only hold a surface charge...

    ..... Philip
    Last edited: May 4, 2014
  7. supernova

    supernova Bobtail Member

    Jan 11, 2014
    Calgary AB
    I had a similar problem that I couldn't figure out, all the batteries were testing good. I would leave truck over night and it would be slow to turn over in the morning . I just figured that the inverter or the fridge was draining them so decided to switch them off over night. This helped a little, but still it was slow to turn and low power in the morning. After many worrying mornings the source of problem turned out to be a simple thing. One of the door pins switch for the under bunk lighting was not working (i.e. not turning the lights off when side hatch was closed) thus hard to find as when you open the bunk from either lifting the bed or either of the side hatches the lights automatically would be on .
    My problem was solved. Maybe not relevant to your problem but worth a look for the simple things. Did you install any new electrical things recently that are wired to permanent live?

    Good luck,
    HopeOverMope Thanks this.
  8. Ysofast

    Ysofast Bobtail Member

    Dec 21, 2013
    I have the same 12 prostar w 13 maxxforce. The load shed was set to come on too early, like 12.2 and you could park your truck and run the stereo for 10 min and it would cry out and shut me down. The dealer can change that setting for you. I agree with the load test, disconnect the positive wires and load test each bttry by it's self. Good luck
  9. Cranky Yankee

    Cranky Yankee Cranky old ######

    Jan 31, 2012
    Green Bay Wi
    if the truck starts fine even if the inverter readout says 10-11 v I would say it is the wiring on the inverter
    isnt making good connection
    also because you say there is a lag after starting before the readout shows 14v
  10. bluerhino

    bluerhino Light Load Member

    Mar 10, 2013
    hi Heavy D in the market for 4 batteries for international 9400i 2006 would prefer 1000 cca or more would appreciate your input plus best place to buy
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