New vs Old Traction Battery for Months-long Storage

Discussion in 'Gen 2 Prius Main Forum' started by sydney2008, Sep 12, 2025 at 9:25 AM.

  1. sydney2008

    sydney2008 Junior Member

    Joined:
    Sep 11, 2022
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    Location:
    Savannah
    Vehicle:
    2008 Prius
    Model:
    Touring
    TL;DR: I love my Prius and I will be replacing the hybrid battery. Dealer quoted $3,100 for a new one, which I'm considering. Main question: For six months of storage, is it better to leave the old (dead) battery in until later, or install the new one now and follow proper storage steps (oil, Sta-bil, 12V disconnect, etc.)?
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    Hi Prius friends! I recently came to terms with the fact that I must replace my hybrid battery. I've been shopping around and was leaning toward a local shop that offers a rebuilt battery, but when it came time to schedule the service, he gave me a "range" of $2,500–3,500, so that's now off the table. My usual dealership (where I now just go to buy OEM parts) quoted me $3,100 for a brand-new battery with installation—not as bad as I expected. As some of you know, I LOVE MY PRIUS, so I’m willing to go there on price (though I’m still checking around with other dealerships).

    My real question is about long-term storage (six months). Would I be better off leaving the current battery in place, knowing it will almost certainly be dead and require towing and extra effort for the eventual install (at an unknown price at that time, given tariffs and whatnot)? Or should I go ahead and get the new traction battery now, with a plan to do all the “storage things” to protect the 12V and other systems?

    I know these cars need to be driven often, and I seriously considered selling her so someone else could keep her on the road. But I just can’t do it. My Sydney is a Touring edition with the exterior and interior colors I love. She only had one owner before me, and I’ve meticulously kept up with maintenance. She has had very little exposure to salted roads. I’ve camped in her many times and even lived in her full-time for a couple of months. I don’t feel there’s any chance I could replace her with a similar vehicle, and it’s reasonable to assume there are fewer of these cars on the road every day. In any case, I am committed to keeping her.

    I’ve read every thread I could find here with recommendations and results. As far as I can tell, none*** describe my specific circumstance, but please point me in that direction if this has already been addressed by the PriusChat community.

    Based on suggestions I’ve gathered here, this is my long-term storage prep checklist:
    • Change the oil (check!)
    • Add Sta-bil to the gas tank
    • Set air controls to recirculate (helps close off mouse access doors)
    • Place Bounce dryer sheets around inside to deter rodents (though stray cats in the area may already help)
    • Disconnect the 12V battery completely (both terminals)—unless disconnecting the white quick plugs is sufficient?
    • Pull the orange safety plug on the hybrid battery (is this helpful?)
    • Leave access from the front of the car with tools ready for reconnection
    • Spray WD-40 into the keyhole for manual entry
    • Apply lanolin-based rust protection underneath the car
    • Inflate tires to the maximum cold pressure listed on the sidewalls

    *** NOTE: I did find a thread that included this quote from @Hayslayer:
    “You will have no 'must drive every day' problems with a new Toyota pack. When new, these packs can sit in a car for a year or more without being used and they will be perfectly fine. The 12V battery will be dead, but the HV battery will be fine. They don't start having self-discharge problems until several years of use. Based on your usage description, that will work great for you.” ( @Hayslayer - your reply is the reason I am now considering this option! )

    If you've read this far, THANK YOU and please let me know what you recommend or what you would do with your Prius in a similar situation!