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Anyone know how to change alternator output for AGM battery

Discussion in '3rd Gen. Tacomas (2016+)' started by ihatemytruck, May 10, 2019.

  1. May 10, 2019 at 1:46 PM
    #1
    ihatemytruck

    ihatemytruck [OP] Professional dumbass

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    Does anyone happen to know how to change the alternator voltage to accommodate the higher charging voltage requirement for AGM batteries?
    I've looked through techstream and couldn't find anything. Any help would be appreciated.
     
  2. May 10, 2019 at 1:47 PM
    #2
    Gunshot-6A

    Gunshot-6A West Coast Randy

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    There are a few companies that have a jumper wire that goes between the alternator and the harness to trick the charging system. Not a techstream item though.
     
  3. May 10, 2019 at 1:52 PM
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    ihatemytruck

    ihatemytruck [OP] Professional dumbass

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    You can "test" the alternator voltage and increase it through techstream, but once you exit the test, it defaults back. There's gotta be a way somewhere in there to change it.

    I've seen the boosters that go into the fuse panels on the earlier generations, but the 3rd gen doesn't have the fuse for it.
     
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  4. Jul 6, 2019 at 3:10 PM
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    Grossomotto

    Grossomotto Complete 3rd Member

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  5. Jul 6, 2019 at 3:18 PM
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    sd1uh8as

    sd1uh8as Well-Known Member

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    While someone still looks into the 3rd gen AGM charging, I went ahead and just put a solar panel and keep it charged through that
     
  6. Jul 19, 2019 at 8:35 AM
    #6
    ihatemytruck

    ihatemytruck [OP] Professional dumbass

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  7. Jul 19, 2019 at 9:37 PM
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    DesertTaco17

    DesertTaco17 Member

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    if you upgrade to agm battery charging needs to be different? I did not know. I just recently bought a NAPA AGM battery
     
  8. Jul 19, 2019 at 9:48 PM
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    Grossomotto

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    The bulk charge from your alternator won’t go to 14.7V that your AGM battery has for a full charge. It’ll still charge it, but some members say only 80-90%.

    Like I said above, an easy solution is to recharge on a 7 stage charger or similar once a month, you don’t have to take the battery out of the truck.

    As you know AGM batteries are great if you’re discharging them with electrical mods, which they can down to 20% several hundred times.

     
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  9. Jul 19, 2019 at 9:52 PM
    #9
    albrow100

    albrow100 Member

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    Not sure how they wired it on 3rd gens
    Anyone have the wiring diagram?

    Most smart charge systems fail safe to full voltage if the circuit from the ecu to the alternator is cut
     
  10. Jul 19, 2019 at 9:55 PM
    #10
    Grossomotto

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    There’s an aftermarket higher output voltage regulator someone came up with for 2nd Gens. He couldn’t get it to work on the 3rd Gens.

     
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  11. Jul 19, 2019 at 9:58 PM
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    DesertTaco17

    DesertTaco17 Member

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    ok new to me. thanks for the info


    will it be detrimental if i don't use a charger to top off? how about using a harbor freight or similar battery tender?
     
  12. Jul 19, 2019 at 9:58 PM
    #12
    Itchyfeet

    Itchyfeet Banned

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    AGM batteries another nope never again thing for me. I like the idea, but they can't handle cold weather at all.
     
  13. Jul 19, 2019 at 9:59 PM
    #13
    Grossomotto

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    I’m sure your AGM will last several years with doing nothing, you’re not going to kill it.

    My understanding is a regular battery tender is for a SLA battery and better to use a multi stage charger for an AGM.

     
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  14. Jul 19, 2019 at 10:06 PM
    #14
    Grossomotto

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  15. Jul 19, 2019 at 10:07 PM
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    DanoT

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    I have an RV but I am not really all that knowledgeable about batteries. Nevertheless I thought that it was the Lithium batteries that can be drawn down very low but AGM, like lead acid, should only be depleted by 50% and then charged up.
    I do know that the main advantages for AGM batteries is that they can be mounted in any position, so ideal for extreme pitch angle when off roading.
    AGM batteries stand up to vibration pretty well.
    AGMs are also idea for mounting inside an RV without needing a sealed vented box because they do not off gas.
     
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  16. Jul 19, 2019 at 10:12 PM
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    Grossomotto

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    I’m no expert, just try to read a lot. Here’s a good article

    https://www.susprep.com/off-grid-power/batteries-101-part-1-depth-discharge/

     
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  17. Jul 19, 2019 at 10:31 PM
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    DanoT

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  18. Jul 19, 2019 at 11:03 PM
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    Boosted_Carrera

    Boosted_Carrera Well-Known Member

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  19. Jul 19, 2019 at 11:42 PM
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    Boosted_Carrera

    Boosted_Carrera Well-Known Member

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    The charging system on a modern vehicle should have no problem charging an AGM battery. I have AGMs on the 911 and RX7 and their alternator amps are about 130. An AGM was a must due to moving it inside for weight distribution. An alternator will not, cannot charge an AGM to full charge. You'll need a battery charger.
    I have them on a trickle charger to keep them happy.

    For future reference to those who have drained it waay below and have a 6/12 volt charger, the charger will *think* it's a 6 volt battery and not switch over to 12v without a boost from another 12v battery *OR* a portable battery jumper.
     
    Last edited: Jul 19, 2019
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  20. Jul 19, 2019 at 11:58 PM
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    Itchyfeet

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