Cost of 12v AGM Battery for 2018 Prius

Discussion in 'Gen 4 Prius Main Forum' started by DaveWR, Jan 6, 2021.

  1. Mendel Leisk

    Mendel Leisk Witness Leader

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    Good points. Yeah with our conventional batteries, it always seemed to help, to take them right out after 3 years or so, shine a light behind (almost always had translucent cases you could just see the levels through), top of the levels with distilled water, clean the posts, and the cable clamps, and give it a charge session as well.
     
  2. johnHRP

    johnHRP Active Member

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    No need AGM battery if it is in engine bay. It is about safety when the AGM is used inside the cabin.
     
  3. sam spade 2

    sam spade 2 Senior Member

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    You don't NEED an AGM battery in the engine bay but..........
    It is a much better choice because of better design and usually longer life.
    It seems to be hard to get a lot of people to check their oil and coolant....ever.
    Expecting them to check the water in the battery is just out of the question.
     
  4. johnHRP

    johnHRP Active Member

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    No, 99% 12 v flooded battery is maintenance free too. Unless you live in 3rd world countries. AGM battery does not live longer either if it is in engine bay. It cost 3x more with probably 50% longer live. Not cost effective.
     
  5. sam spade 2

    sam spade 2 Senior Member

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    That first statement is total BS, John.
    My guess is half or less.
    A really LOT of them on the shelf at places like WalMart, Autozone, NAPA, etc still have removable caps.

    And those last two sentences directly conflict with each other.
    First you say it does NOT live longer.......and then you say it has 50% longer life.
    Also the cost usually is NOT 3X but more like 1.5 to 2X.

    Your "facts" aren't.
     
  6. johnHRP

    johnHRP Active Member

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    Thanks for correcting me. Its lifespan is about 7-8 years when driven regularly with the AGM battery in Prius. Part of it is probably because it is inside the cabin, lower temperature. The alternative wet battery cost about $90 and AGM from Yuasa is about $200. It is about 2x more these days.
    Full charge AGM is about 14.8 V vs regular battery 14.4 V open circuit. I think it is fine to use AGM if the car is not designed for AGM but not the other way around.
     
  7. sam spade 2

    sam spade 2 Senior Member

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    I'm sorry but that is wrong too.....unless you are talking about the normal CHARGING voltage, which varies all over the place.

    A conventional wet cell battery when fully charged will not MAINTAIN a voltage above about 12.6 or 12.7.
    An healthy AGM fully charged often will maintain 12.9 open circuit.
     
  8. johnHRP

    johnHRP Active Member

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    Ah yes. 12.4-12.8 V. It was a typo. The charger is only 14.-14.5 V, it is imposible to get the battery more than charger open voltage.
     
  9. pilotgrrl

    pilotgrrl Senior Member

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    I replaced my 2016's 12 volt battery recently. It was about $200 at a local auto parts store. They installed it for me at no additional charge. A much better experience than changing out my Gen 2's battery, for sure!
     
  10. johnHRP

    johnHRP Active Member

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    2016 Prius used regular battery and installed inside the engine cabin. It is a regular wet cell battery, not an AGM. You can always check Advanced Autoparts, they always have 30-40% online coupons, and pickup locally. I did it often and sometime the parts are also can be picked up in Carguest stores too.
     
  11. sam spade 2

    sam spade 2 Senior Member

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    But there is little disagreement that an equivalent AGM would be a better choice......even if it is more expensive.
     
  12. johnHRP

    johnHRP Active Member

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    AGM definitely last longer compared to wet cell for high vibration applications. I believe AGM also handle heat not as good as wet cell but handle freezeng cold much better. For that reason, Manufacturer use regular wet cell when it is under the hood. Wet cell usually give larger CCA per volume too.
     
  13. sam spade 2

    sam spade 2 Senior Member

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    I think your assumption is wrong.
    They use a conventional wet cell battery because they can save a few bucks per car by doing that.
     
  14. johnHRP

    johnHRP Active Member

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    It is q simple fact that AGM was mainly for deep charge application, safety reason inside cabin, and rough terrain vehicle, or in freezing area.

    It is not cost effective and no benefit in most car application inside hot engine bay. AGM need more stringent charger management too. The claim that AGM can last 2x longer is on high vibration application, and deep cycle, not 8 or 10 years average lifespan. Many prius 2nd, 3rd, owners have their battery lifespan about 5 years, similar to wet cell, even inside cooled cabin. It's even worse if you use AGM on 4th gen inside the engine bay.
     
    Mendel Leisk likes this.
  15. sam spade 2

    sam spade 2 Senior Member

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    Well except maybe for the fact that you don't have to check the "water level".
    Which most people won't do anyway, resulting in an early death for a conventional wet cell type as it goes dry after a couple of years.

    Then.....my experience, and the experience to tens of thousands of other vehicle owners has been exactly the OPPOSITE of what you are preaching. I will never own another conventional wet cell battery, not even in my lawn mower.
     
  16. johnHRP

    johnHRP Active Member

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    All Wet cells we get in the USA are all sealed units VRLA, never need water checking. That's relatively the same in terms of no maintenance, just clean and spray silicon/dielectric grease the first time we install them. Some wet cells battery can still be opened but may void the warranty. The main cause of failure battery is sulphation(undercharged <11.8V) and corrosion (overcharged), especially on the PbO positive electrodes that are made out of paste, pressed, and dried. The negative plates are pure Lead, usually, last much longer, and often can be refurbished. The other failure points are the contact from the positive plates to the Lead terminals that are prone to corrosion if it is overcharged. These problems are the same in both wet and AGM style batteries. Generally speaking, the electrodes plates are sulfated every time we discharge it and recover if we charge it back to close to 100% soon enough. If it is undercharged for a long period of time or below 11.8V, the sulfated area cannot be recovered, and if it is recovered, that sulfated-lead microcrystalline are removed/etched and sink under the plates. Recovering will increase the capacity back but also degrade the battery at the same time.
    Our DCtoDC converter is very smart, it outperforms any Add-on charger like CTEK or NOCO if we use it regularly. We need these chargers if we ever leave the car for more than 1 month. CTEK5 is fine if your garage is not humid, otherwise, get NOCO5 with coated PCB and contacts.
    Turn the car on once a week at least for 30 minutes travels will guarantee last long battery, it will rarely drop below 80% charge state.
     

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    #56 johnHRP, Jan 31, 2022
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  17. sam spade 2

    sam spade 2 Senior Member

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    About 30 seconds with Google search proved that statement to be absolutely WRONG.
    You actually have some good information to share.
    Too bad that it is contaminated with off the wall crap like this.
     
  18. johnHRP

    johnHRP Active Member

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    For cars, 99.999% are VRLA even in Walmart. You may find the primitve non VRLA for nische market. For the past 20 years, I have never found any wet cell battery in Autozone, Advance, Sams club, etc. Not even for the 1995 Nissan Sentra. They are all VRLA. Unless you are a farmer that may have unique equipment.

    The last time I saw someone add water to the battery was my great grand pa on his 1970s Honda motorbike.
    Back to the topic, you do not need an AGM battery when it is inside the engine bay. Just a waste of money and not better, not life longer, just plain ignorance.
     
    #58 johnHRP, Jan 31, 2022
    Last edited: Jan 31, 2022
  19. Mendel Leisk

    Mendel Leisk Witness Leader

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    The stock battery on 4th gen come with uncovered fill caps, judging from pictures.
     
  20. sam spade 2

    sam spade 2 Senior Member

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    Well you sure would be an expert on "just plain ignorance".
    And stupidity too.
    I quit.