Are you surprised my stock 12V battery is still working ?

Discussion in 'Gen 4 Prius Main Forum' started by Chris Wolfgram, Oct 21, 2021.

  1. Chris Wolfgram

    Chris Wolfgram Active Member

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    Okay, so its only a 2019.... But I have close to 80K miles on it (mostly Uber) AND I constantly run the AC + an amplifier which probably pulls more amps "continuously" than the 30 amp recommended max.... Honestly, I'm surprised I haven't killed it already.
    What is going to be the first sign that this battery is about to bite the dust ? Sure be nice to catch that, and rectify it before it actually happens....
    Depending on when that were to happen, it could potentially cost me like a $1500 loss (on a Friday afternoon, before a busy weekend).
     
  2. kevinwhite

    kevinwhite Active Member

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    The 12v battery doesn't do much once the car is in 'Ready'.

    The DC-DC converter feeding the 12v has about 100A capability with the car taking about 10-20A(depending upon whether the engine is running). You can take 80-100A without draining the battery at all.

    The A/C probably doesn't use any significant amount of 12V power. Your amplifier taking 30A with no problem.

    I have used mine feeding a 1200W inverter to power the house during a power cut with no problem. It was taking up to about 70A with the load I was giving it.

    kevin
     
  3. MalachyNG

    MalachyNG Member

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    I replaced the 12v on my 2016 this spring with about 100k miles. What really kills 12v is if your car sits unused for a long time or if the 12v drains enough you need a jump start. If that happens a few times then you'll need to think about replacing it.

    But driving every day is probably better for it and you may have quite a few miles left to go. You can always stop by an auto parts store and have them test it. Many offer the service for free. For gen 4 they moved the 12v to the engine bay and increased the size (still an annoyingly expensive non-standard one). The 12v in my 2013 survived well past 100k miles before I needed to change it out. So I'd recommend getting it tested around 100k miles or if you ever find you need a jump start for whatever reason.
     
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  4. alanclarkeau

    alanclarkeau Senior Member

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    Mine is still going strong - has a few days idle most weeks since lockdowns - 5½yrs old almost. I'm hoping it outlasts my use of the car. Haven't bought a battery for 20 years - buy a new car instead.

    Only problem is - stocks of new cars are very depleted at the moment. Most dealerships, most brands are showing stock of many models "for test drives", but none for sale.
     
  5. fuzzy1

    fuzzy1 Senior Member

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    No.

    Unless your audio system has repeatedly drained the battery to or near 'no-start' while the car isn't in 'READY' mode.
     
    #5 fuzzy1, Oct 21, 2021
    Last edited: Oct 21, 2021
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  6. Salamander_King

    Salamander_King Senior Member

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    If it is a 2019.... But you have only 80 miles on it. Then, yeah, I would be surprised that the original 12v is still in good condition. If you are driving that often, you have nothing to worry about your 12v battery dying anytime soon. Enjoy.
     
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  7. Chris Wolfgram

    Chris Wolfgram Active Member

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    Honestly, as long as the inverter is working properly, I'm not sure how one would ever drain their 12V battery, regardless of the load ? Seriously, I can (and often had "all" of my accessories on, including AC on high + plus beating my stereo, and yet never any flickering of lights, or any other indication of dipping voltage ?
    As I have said before, aside from having a max safe limit of amperage that the inverter can make, it is a super stable, solid setup.
     
  8. Chris Wolfgram

    Chris Wolfgram Active Member

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    I actually hear the same thing about the big, hybrid battery. Honestly, I think this pertains to most batteries, unless maybe its some sort of special purpose type ?
     
  9. Chris Wolfgram

    Chris Wolfgram Active Member

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    True :(
     
  10. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I replaced my 12 volt battery after 7 years, my headlights were getting a lot brighter once I put the car in Ready.
     
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  11. Mambo Dave

    Mambo Dave Active Member

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    What is 'Ready' mode? Do you guys mean turning the car on?
     
  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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    In Toyota-speak there’s “on” and “ready”. On (achieved with 2 start button pushes without brake pedal depressed) is almost full on, but engine won’t start, and I don’t believe car will shift to D. Ready (one push of start button with foot on brake) is fully operational.
     
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  13. fuzzy1

    fuzzy1 Senior Member

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    The AC compressor runs from high voltage, not 12V, so shouldn't be an issue here. Though the ventilation fans do run from 12v.

    There is a dashboard "READY" light. If this light isn't turned on, then it isn't 'Ready' and can't drive. Also, the HV -> 12V inverter is not running, so the 12V will be subject to getting drained from accessory loads.
     
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  14. Chris Wolfgram

    Chris Wolfgram Active Member

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    Wow, learn something every day. I didn't even know I could do that. But still not sure why I ever would ?
     
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  15. Chris Wolfgram

    Chris Wolfgram Active Member

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    Okay, good point. But what about my amplifier which runs at probably 50-125% of the max recommended amp draw (a large % of the time I'm using the car) off of the 12v side in my car ? No effect on the 12v battery life ?
     
  16. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Yeah you don't want to do that regularly; it burns through the 12 volt battery pretty fast, even faster than accessory mode (one push of start button without foot on brake). On mode is needed for brake bleed procedure; that's one instance I can think of, and use.
     
  17. rjparker

    rjparker Senior Member

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    If the car is in Ready the inverter is carrying the load. But the car in the On or Accessory mode (just like a conventional car with an alternator) will drain the little Prius battery fast. The agm battery is designed to take discharges better than a flooded lead acid battery but not if drained daily. So its useful to know what mode your in.
     
  18. Mendel Leisk

    Mendel Leisk Sand Pounder

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    When I do brake bleed in accessory mode, I have a smart charger connected at same time. I think that's what dealerships do when doing software updates too?
     
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  19. Salamander_King

    Salamander_King Senior Member

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    Did it ~10 years on HCH rims with no ill effect. Also did it for 3 winters on Gen3 without a problem. Never bought separate rims for those two cars. If a tire shop offers free changeover, it is the most economical way to have snow tires. Even if the change over must cost, it would be the same price as taking a car for TPMS reset at ~$15/tire. But after buying separate rims for my first PP and also buying tools to change or rotate tires DIY, I have a vested interest in doing this DIY, otherwise, all the money I paid for tools would go wasted. I bought separate rims for our other car and my son's car. With three cars, if I had to pay to have the tires changed twice a year on three cars, then the cost of the jack stands, floor jack, torque wrench, and separate wheels would be paid off fairly quickly. Still, I think it is less expensive to use a single set of rims and is much less hassle than DIY in general. When I can no longer lift the tire on the wheel by myself, I am going to just use the tire shop storage option and have them change the tire twice a year on the same rims. That is if I am still doing winter driving at that age. LOL
     
  20. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I kinda hit that wall, especially with our daughters Pilot wheels, but switched technique:

    First off, a couple of fashion accessories: a headband light, and durable boots (steel toes).

    Raise the car so the tires are at most 1” clear.

    Roll wheel into position, as close as possible to hub, with holes aligned with studs.

    Sit comfortably close, hook your toes under the tire, and lift up-and-on, just steering with your hands, and headlamp helping with alignment.

    Get one nut started at bottom, and you’re away. :)
     
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