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Battery/Charging System Issue?

Discussion in '2nd Gen Tundras (2007-2013)' started by Rennsr5, Jul 15, 2019.

  1. Jul 15, 2019 at 6:54 PM

    Rennsr5 [OP] New Member

    Jul 15, 2019
    First Name:
    2010 Black SR5
    No mods
    Hey guys, first time post! I’ve pulled a lot of good info off here the past couple years though! Thank you!

    Got a 2010 SR5 4x2 - 229,xxx. Had my truck for about 5 years now. Never had an issue, and put 170k miles on it. Regular maintenance performed by dealer.

    The issue...
    2 weeks ago I decided to clean the interior, like an idiot, I forget to shut my headlights off and left the doors open. It drained my battery down to 7 volts. Put it on the boost charger and fired right up. Of course charging at around 11.5-11.6, since it was so dead. Battery is only 4 years old.

    Ran errands for about an hour, never shut it off. Got back seemed to be running fine..shut her down. Pulled the negative cable off, and put it on the battery charger for 2 hours @ 10amps. Battery came right back. It sat for an hour off the charger...holding @ 12.6v disconnected.

    Cleaned both posts up, Cable ends, and the top of the battery. hooked up the cables, fired her up and it didn’t sound right...Looked down RPMs at 300-400 and it stalled, tried again.. stayed running still holding st 300-400 rpm and voltage gauge well below normal(what I’m used to seeing the last 5 yrs). Grabbed the volt meter..12.5v and dropping! Oh it’s not charging, duh.

    Nursed it back to my house, 15-20 min drive, it stalled at every stop I made UNTIL! I pulled in my driveway. Lol..Voltage gauge went up, idling at 700-800 rpm. Grabbed the Volt meter and reading at 13.8..wtf. Turned it off battery reading 12.55v.

    Parked it for a week, while out of town, came back and it fired right up. I did order a new TYC 150amp alternator figuring the regulator was starting to go. So I threw that on this past Saturday(I will say what a pain in the) only took about 3hrs though. First drive out with the new alternator, third stop sign, RPMs dropped along with the voltage gauge. I watch the voltage gauge move with anything to do...A/C, headlights, hitting the brakes.

    Went by Advanced Auto, they put the tester on it.
    640/700 CCA Battery
    13.87 Charging - no load
    13.74 Charging - Full Load (a/c, lights, etc. )

    I also did...
    0.04 ohms neg terminal to chassis
    0.05 ohms neg terminal to motor
    0.025 voltage drop pos terminal to top of battery

    I used to be a mechanic, but I’ve been out of the game for about 7 years now, and I feel like I’m missing something. I plan to ohm positive terminal to starter and alternator(can’t find my damn 10’ alligator leads!) Along with trying my friends battery.

    Sorry for the long post, just trying to give all details why I scratch my head.


    BTBAKER likes this.
  2. Jul 15, 2019 at 7:14 PM

    Tierhog SIG-AHOLIC

    Feb 7, 2018
    First Name:
    2016 Tundra Crewmax Limited 4WD
    Mostly stock/TRD accessories/Morimoto XBs
    Damn. Had to retype this a hundred times because I reread your post. Your out of options Chris. The battery or alternator must have been tested incorrectly (emphasis on battery). Screw it.. Get an AGM and new terminals. You've done everything else. Lol

    I know that's not helpful per se but given your history, I can't think of what else I would do.

    I changed my old acid type battery every 4 years as SOP before I switched to Northstar AGM.
  3. Jul 16, 2019 at 4:21 AM

    rebmo 2020 Crewmax Limited 4wd Silver/Black

    Dec 24, 2014
    Rural SE Wisconsin
    2020 CM LImited 5.7L V8 4WD
    I have read on here that sometimes after disconnecting the battery to clear codes, it can run rough for a bit and settles down when the ecm sets up the right running settings for your use patterns. This has not happened to me after changing my battery so perhaps someone can chime in that has had this happen and further advise. I hate to see you shotgunning if this is your issue.
  4. Jul 17, 2019 at 2:40 PM

    JohnLakeman Burning Internet Daylight

    Feb 21, 2019
    Outside of Weird, TX
    2017 MGM DC TSS 4.6L
    TRD Pro grille, 2018 LED Headlights, Undercover Flex bed cover, Neoprene seat covers, Bed/tailgate mats, Power tailgate lock, auto headlights, illuminated key switch
    I would be surprised if a 4 year old battery came back from a "black hole" discharge. I am even more surprised that you would force your poor Tundra alternator to try and bring it back from the dead. :D

    If I understand your OP correctly, the Advance Auto battery test seems suspect. Battery voltage can not be measured correctly while the battery is being charged; I believe they were actually measuring the charger voltage. Battery voltage readings over 13.4V should be suspect in my opinion. Check battery voltage with the charger "off". If the battery can be recharged to 12.6 volts, and will hold that charge overnight, then a week, your battery will probably be dependable for just a little bit longer.

    The best way to have recovered your battery from a "black hole" discharge would have been to first attach a "smart" charger with low voltage and medium charging current like a CTEK Multi US 7002 (14.7V, 7 amps, link below) to fully recharge the battery before starting the truck. Depending on the battery type, the CTEK 7002 can recharge a battery from about 2 volts. In some cases, this may require "tricking" the charger by using a second charged battery connected in parallel to the discharged battery, and attaching the charger leads to the charged battery. Using your truck alternator to recharge a battery will likely shorten the alternator's life.


    I just installed a new Northstar AGM in my 2017 Tundra, and maximum voltage after having it on the CTEK maintenance charger for maybe a week is 13.2-13.3V.

    For future battery health monitoring, you may want to look at inexpensive testers (link below). These have pretty much replaced the old load style testers, and work by measuring the voltage and resistance across the battery, and comparing it to the original rating. Results include current CCA available, State of Charge, and State of Health. Report can be downloaded to a PC from printing, allowing comparison to previous tests.


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