Forum Discussion

GA1dad's avatar
GA1dad
Explorer
Dec 11, 2016

Battery Tenders

Keep in mind I'm a noob to the diesel world,,,,,

So twice now the batteries have run down on my Duramax from lack of use. I'm starting to look for an inexpensive tender that I can mount to the vehicle. I'm kinda looking at the Tender Jr. 800. I know the 800 milliamps is not much for actual charging,, but I suppose it could maintain an already fully charged system. I want to mount the unit in the engine compartment somewhere, then hard wire at the battery terminals and have a 120 volt pigtail coming out of the grill.

My question is if I hardwire it to the terminals, would it be harmful to the tender if I drove the vehicle with it still hooked up ( not powered up,, but still hooked to the battery )., While running, will the current from the alternator reverse into the tender and burn it up?

Thanks in advance folks.
Tow Vehicles

27 Replies

  • austingta's avatar
    austingta
    Explorer
    Dec 12, 2016
    My friend Dale went on a 3-month road trip and when he got back his new Cadillac started right up.
  • Lynnmor's avatar
    Lynnmor
    Explorer
    Dec 12, 2016
    Trackrig wrote:


    My Ford truck will die if I leave it for about eight weeks, but what really gets me is the DWs Ford Escape that goes dead in about ten days. It's been two two dealers and both said that was the way Ford designed them, there's nothing they could do.

    Bill


    I very much doubt that the dealer is starting and letting run all the new and used vehicles on the lot every few days. Doubtful they could sell anything when most won't start for a demo ride.
  • Bedlam's avatar
    Bedlam
    Moderator
    Dec 12, 2016
    beergardens wrote:
    mkirsch wrote:
    "Have truck checked..."

    For what, exactly? Any good mechanic will tell you that minor electrical gremlins are extremely tough to track down, and to pay them to do it may well cost more than the vehicle is worth.

    It's a routine matter for a technician to go over the charging system. Test the alternator output, load test AND cell test the batteries, and measure the ignition-off draw. If the draw is over 50mA after everything has timed out, then it's time for the OP to decide if he wants to hunt it down, which often isn't as horrifying as people make it out to be, as long as the tech is knowledgeable.

    It's pretty easy to use an ammeter between the truck and battery and start pulling fuses until you find the biggest draws. This will isolate the problem down to one circuit. You may find it is as simple as a cigarette lighter adapter that is always running or a glove box light that never turns off.
  • Trackrig's avatar
    Trackrig
    Explorer II
    Dec 12, 2016
    mkirsch wrote:
    "Have truck checked..."

    For what, exactly? Any good mechanic will tell you that minor electrical gremlins are extremely tough to track down, and to pay them to do it may well cost more than the vehicle is worth.


    My Ford truck will die if I leave it for about eight weeks, but what really gets me is the DWs Ford Escape that goes dead in about ten days. It's been two two dealers and both said that was the way Ford designed them, there's nothing they could do.

    Bill
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Dec 12, 2016
    austingta wrote:
    GA1dad wrote:
    gbopp wrote:
    How long does your truck sit between uses?


    A couple of weeks and it goes down enough to keep it from starting. It'll roll over a few times, then click/click.


    There is something wrong for sure. The ECM and other things that use current don't use very much at all.

    2 weeks and you should be able to start it.

    4 weeks, less than 50% chance.
  • beergardens's avatar
    beergardens
    Explorer
    Dec 12, 2016
    mkirsch wrote:
    "Have truck checked..."

    For what, exactly? Any good mechanic will tell you that minor electrical gremlins are extremely tough to track down, and to pay them to do it may well cost more than the vehicle is worth.

    It's a routine matter for a technician to go over the charging system. Test the alternator output, load test AND cell test the batteries, and measure the ignition-off draw. If the draw is over 50mA after everything has timed out, then it's time for the OP to decide if he wants to hunt it down, which often isn't as horrifying as people make it out to be, as long as the tech is knowledgeable.
  • mkirsch's avatar
    mkirsch
    Nomad II
    Dec 12, 2016
    "Have truck checked..."

    For what, exactly? Any good mechanic will tell you that minor electrical gremlins are extremely tough to track down, and to pay them to do it may well cost more than the vehicle is worth.
  • boshog's avatar
    boshog
    Explorer
    Dec 12, 2016
    Chuck_thehammer wrote:
    answer is not so easy..

    the older the battery . the faster it discharges.
    I avoid the cheaper tender types.. Deltron Battery Tender was top. others are catching up.

    1.5 amp with 2 batteries.. adding a single 2 amp diode will stop back draw.

    over 3 weeks I can see a slow start. but NOT a No start.. if it continues have truck checked..

    do you have add-on electronic devices in truck, they may not be turning off.


    Keep in mind diodes also have a voltage drop, enough drop and you may be doing a disservice to your batteries, particularly if their chemistry is AGM.
  • Snowman9000's avatar
    Snowman9000
    Explorer
    Dec 12, 2016
    Yeah the batteries could simply be old and feeble.

    My 2004.5 Duramax has a parasitic draw of 21 mA. Which I think is not much?? I was chasing a battery problem recently. Starting was weak on a good day, and got worse as the truck sat. It turned out to be a corroded + terminal on one battery. Prior to that I had never seen corrosion in a GM style terminal. I cleaned it up and everything has been great since.
  • Chuck_thehammer's avatar
    Chuck_thehammer
    Explorer
    Dec 12, 2016
    answer is not so easy..

    the older the battery . the faster it discharges.
    I avoid the cheaper tender types.. Deltron Battery Tender was top. others are catching up.

    1.5 amp with 2 batteries.. adding a single 2 amp diode will stop back draw.

    over 3 weeks I can see a slow start. but NOT a No start.. if it continues have truck checked..

    do you have add-on electronic devices in truck, they may not be turning off.

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