2017 Prius Prime Advanced replacement battery

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by gklipfel, Oct 21, 2021.

  1. gklipfel

    gklipfel New Member

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    I just had to replace the 12V battery in my wife's 2017 Prius Prime Advanced. The error message when she tried to start was "12 volt battery low". The battery was about 4 years old. Toyota, AutoZone and Napa were all back-ordered with no shipping date available. Thanks to a YouTube video, I tried O'Reilly's. They do currently have some in stock. Part #: 140REXT Line: SSB. Exactly the same dimensions as the Yuasa battery it replaced. Installed and working.
     
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  2. Salamander_King

    Salamander_King Senior Member

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    Yeah, it is a small and weird-size battery that seems to be not stocked all the time. It is a known issue that PP and maybe to some extent all Gen4 have phantom draw while not being driven. 4 years on OEM may be just about average in a hot climate. It is a good idea to keep a portable lithium jump pack just in case the 12v battery fails to start the car.
     
  3. EdPalmer42

    EdPalmer42 Member

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    It's not just the phantom draw.

    The 12V charging system on the PP is substandard. It assumes that all Primes are in Japan with a rather benign climate - not too hot or cold. So there is no temperature compensation on the 12V charging voltage. If your weather is usually between freezing and room temperature, you're good. If it gets hotter you overcharge your battery - but you can add water to the battery so that's not a huge problem. What's worse is if your weather gets cold. Then the battery is undercharged. I don't think it could become so undercharged that the battery could freeze (yes, my weather can get that cold!). The PP would give up long before that would happen and you'd need to boost or charge the battery.

    Temperature compensation has been used in car battery charging circuits for decades. I've got an automotive training book from 1977. The chapter on voltage regulators has a section on temperature compensation. One of the review questions at the end of the chapter is "Why is temperature compensation needed on a voltage regulator?". Maybe I should send this book to the Toyota engineers in Japan. Do you think they'd appreciate it? ;):X3::ROFLMAO: They've basically decided that the battery is a consumable item and there wasn't enough reason to provide a competent charging system.

    When I realized this problem existed, I got a temperature-compensated battery maintainer to give the battery a fighting chance. So far, as expected, I haven't had to use it during the summer but, also as expected, I have needed it in the winter. I watched the battery voltage drop lower and lower and eventually the PP gave up and reported 'battery low'. A quick boost from a lithium booster and it was happy. Once that test was over, I've never let the battery drop that far.

    Ed
     
  4. john1701a

    john1701a Prius Guru

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    What were you doing to cause (and monitor) that? We have two 2017 Prius Primes and live in Minnesota. The 12-volt battery has never exhibited any issues whatsoever, even in the extreme cold. Of course, all it does it boot the system. So, there really isn't a need for much power.
     
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  5. Salamander_King

    Salamander_King Senior Member

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    Apparently, Toyota is not the only car manufacturer thinking this way. My son's 2015 Honda CRZ hybrid is on the third 12v battery. He bought it used two years ago and it came with an already replaced aftermarket 12v battery. It needed to be replaced earlier this year. I don't know how long this one will last, but I am expecting an average of 2 years. Yeah, connecting it to the maintainer may prolong the life, but my son doesn't want to bother with it. He thinks every 2 years buying a ~$100 new battery is easier. It's cheaper than buying a set of tires every 40K.

    But this is just one data point. We have another car by Nissan. It's a 2014 hybrid, but the battery is still original OEM and showing 80% health on a load test.

    I worried about my 2020 PP's 12v battery draining during last year when I was not driving it often enough. But from what I have checked during the undriven period, as long as I drive more than 1 hour/week, the 12v stays reasonably charged and will last OK length. I did not have to change the OEM 12v battery on the 2017 PP after 2.5 years. I don't expect I will be needing a new 12v battery sooner than that on my current 2021 PP. And I don't expect to keep the car longer than 3yrs/36kmiles, so no point in checking its health or putting on a maintainer. But I do carry a lithium jump pack in a car just in case.
     
    #5 Salamander_King, Oct 23, 2021
    Last edited: Oct 23, 2021
  6. sam spade 2

    sam spade 2 Senior Member

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    And another self-appointed "expert" checks in. :eek:

    Almost everything you said in that post is either wrong, misleading or incomplete.
    You can't add water to an AGM battery.....or shouldn't at least.

    Automotive charging systems in general were a "brute force" design with not much regulation and certainly not ANY temp. compensation for about 60 years or so. Many ran close to 15 volts all the time and required frequent water addition to the battery.
    The maker of the car didn't really give a rats behind if you had to change the battery more often than needed.

    Then electronic voltage regulators came into wide use......maybe in the "80s......and they did a MUCH better job of providing an appropriate charge when needed that.......again the car makers had no real incentive to worry about temp. compensation, so they didn't......and still don't. The difference that it would make would be tiny in most circumstances anyway.

    There are a LOT more important things to worry about.
    Automotive charging systems these days are really quite good, except with bringing back a battery that is almost totally dead.
     
  7. Salamander_King

    Salamander_King Senior Member

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    Just so you know. We are on the Prius Prime thread. You should have known this by now. It does not have an AGM 12v battery. It is a regular flooded lead-acid battery. And yes the battery has the removable well cap.
     
  8. EdPalmer42

    EdPalmer42 Member

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    This was over many days of "pandemic" driving - i.e. short trips and not very many of those. A long commute or a garage would minimize the effect of the too low voltage but I have neither of those. The monitoring was done with the BM2 battery monitor which is widely available under various names. It permanently mounts on the battery and continuously measures and stores the voltage. Data is downloaded to your phone via bluetooth.

    You're quite right that all the 12V battery does is boot the system. I've measured the battery drain during startup and I think the drain was something like 20 - 25A which would mostly be due to things like fans, pumps, etc.

    Ed
     
  9. EdPalmer42

    EdPalmer42 Member

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    I think it's fair to say that the temperature in the New England area would be similar to Japan. Sort of benign if you don't look too close. ;) I live in the middle of the Canadian Prairies where temperatures routinely go above +30C (85F) in summer and below -30C (-20F) in winter. Not benign at all and really hard on things like car batteries. Our cold winter temperatures really show the limitations in the PP charging system.

    Ed
     
  10. Salamander_King

    Salamander_King Senior Member

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    Compared to your climate, ours is certainly temperate but still considered to be much colder than most of Japan except maybe the northern most part of Hokkaido. I use to live not too far away from Winnipeg on the US border side where winter temp could dip below -30C (-20F) usually. However, even here in northern New England, we do get certain numbers of days with temperatures close to or less than that. I live close enough to the Canadian border. Our climate is very similar to that of some Eastern Provinces of Canada, like New Brunswick.

    NWS JetStream - Climate
    D - Moist Continental Mid-Latitude Climates
    Moist continental mid-latitude climates have warm to cool summers and cold winters. The location of these climates is poleward of the "C" climates. The average temperature of the warmest month is greater than 50°F (10°C), while the coldest month is less than -22°F (-30°C). Winters are severe with snowstorms, strong winds, and bitter cold from Continental Polar or Arctic air masses.
    upload_2021-10-23_17-11-52.png
     
  11. EdPalmer42

    EdPalmer42 Member

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    As Salamander_King said, the PP doesn't use an AGM battery. Never has. I've checked the water level on my 2020 PP twice and added water once.

    You'll have to take that up with Goodheart-Wilcox who published the "Automotive Encyclopedia" in 1977 (790 pages, hardcover) that I referred to earlier. The chapter on voltage regulators talks about both electromechanical and solid-state regulators with temperature compensation. One electromechanical regulator they discuss is the Autolite Alternator Regulator which looks like it was used mostly in the 1960s.. The temperature characteristics are as follows:

    50F --- 14.3 to 15.0 V
    75F --- 14.1 to 14.9 V
    100F --- 13.9 to 14.7 V
    125F --- 13.8 to 14.6 V

    Obviously, these numbers are sloppy by today's standards and are likely wrong for todays batteries, but the idea was important enough to not just design them in, but to specify them in the adjustment procedures.

    Yes, there are. What makes this issue worthy of comment is that it's been known for so many decades that it's something you just don't think about. You just expect it to be there.

    Ed
     
  12. sam spade 2

    sam spade 2 Senior Member

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    Oops. Sorry for the oversight.
    That is assuming that it still has the same type battery that it CAME with.
    :)
     
  13. sam spade 2

    sam spade 2 Senior Member

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    I certainly don't. At some point, shortly after that book was published no doubt, many/most/all of the car makers became obsessed with stretching their profit at the expense of quality.
    Just because that technology existed doesn't necessarily mean that they USED it.
     
  14. tchan2700

    tchan2700 Junior Member

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    Thanks for this, I just ordered one and will get it installed tomorrow. I too have a 2017 advanced.
     
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