Harm in delaying replacement of 12v battery?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Johnny Sasaki, May 4, 2020.

  1. Johnny Sasaki

    Johnny Sasaki New Member

    Joined:
    May 4, 2020
    5
    0
    0
    Location:
    SF Bay Area
    Vehicle:
    2007 Prius
    Model:
    Base
    Hi there,

    Hope y'all are safe in recent times. With the current situation we haven't been using our 2007 Gen 2 Prius as often as before, and yesterday the car didn't respond to the SmartKey when trying to unlock the doors -- we had to pull out the manual key. When powering up the car, the engine wasn't starting, the navigation display remained off and the dashboard lights just kept blinking. Based on what I've read, the symptoms seem to be indicative of a dead/dying 12v battery.

    Our Prius was bought used as a secondary car and as far as I'm aware it might still have the original battery (despite being over 13 years old, it has fewer than 80k miles on it and was used regularly for a very short commute). We don't anticipate using it often if we were to replace the 12v battery immediately.

    Is there any harm in holding off replacement of the 12v battery for a few weeks or even months? We would be OK with having to do the battery replacement in the garage the car is currently parked in. I'm mostly concerned about preserving the health of the hybrid battery pack and won't put off replacement if that is at-risk.

    Thanks!
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    90,868
    40,823
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    welcome!

    a 2007 hybrid battery is definitely at risk from sitting. i would try charging the battery, get a jump pack, keep it on a trickle charger, or whatever it takes to be able to drive the car once a week for 30 minutes.

    buying a new battery now with a battery maintainer would also work, and it won't degrade sitting idle with the maintainer on it.
     
  3. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

    Joined:
    Oct 17, 2010
    42,046
    30,129
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    If you're really mothballing: charge it up and then disconnect the negative cable.
     
    frodoz737 and Johnny Sasaki like this.
  4. fotomoto

    fotomoto Senior Member

    Joined:
    Apr 22, 2009
    5,297
    3,533
    0
    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    Letting that original HV battery sit for weeks or months will likely be the straw that breaks the camel's back.

    OTOH, the car is in a mild climate which is beneficial to battery life. So......

    GOOD LUCK!
     
    Johnny Sasaki likes this.
  5. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,529
    1,892
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    What is to be gained by waiting ?
    You can use a jump or a booster pack or a battery charger and extension cord to charge up the battery so you can drive it somewhere for a battery.
    Auto parts shops and repair shops are open now.
     
    Johnny Sasaki likes this.
  6. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,768
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I think the OP without malice is doing a bit of bait and switch with the question and concern here.

    There's no harm, it just comes down to what you want to do. If the 12 volt is failing, I wouldn't expect it to get better through continued non-usage and waiting. But once it fails, it's not really going to get much worse. You face the same challenges you would at any time with a failing 12 volt battery and a Prius.
    It's really up to you whether you want to replace it tomorrow, or 4 months from now. Just know of course if you want to start the vehicle all the risks and challenges of doing so with a failing/failed 12 volt battery obviously exist.
    You could try charging it, and seeing how much revival it gives you.

    13 year old Prius, not being driven, I would assume the HV battery is at risk.
    But that's kind of a separate issue, and determination.
    If the HV battery is failing, replacing the 12 volt won't stop that process.
    You may not know whether the HV is failing unless you 1st replace the 12 volt, but replacing the 12 volt won't preserve the health of your hybrid battery pack.

    To me? All decisions would be made on how much driving I intended to do right now and in the short term. If it's not much at all? I'd just try charging the existing 12 volt battery and seeing what happens. Either it works or it doesn't.
    Personally, I'd be hesitant to want to invest into "New" things I'm not going to use.
    I'd want to hold off on investment until I was closer to using the vehicle under my normal demands. Put a new 12 volt, and/or a new Hybrid Battery into a vehicle that is going to almost immediately just sit? That wouldn't be my choice.

    * Edit
    I should add there is no harm in waiting to replace the 12 volt, as long as it is structurally in good shape. That is no leaks, or cracks.
     
    #6 The Electric Me, May 4, 2020
    Last edited: May 4, 2020
    Johnny Sasaki likes this.
  7. Johnny Sasaki

    Johnny Sasaki New Member

    Joined:
    May 4, 2020
    5
    0
    0
    Location:
    SF Bay Area
    Vehicle:
    2007 Prius
    Model:
    Base
    Thanks all!

    It sounds like non-use won't make a dead 12v battery get worse, but could make an ok/healthy HV battery go bad.

    I'll try to get the 12v boosted sometime in the next week -- so regular driving is needed to keep the HV battery from going bad prematurely? I'm not surprised by the 12v going kaput but before this event the car has been pretty good overall.
     
  8. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,529
    1,892
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Absolutely wrong. Backwards, in fact.

    The 12 V battery will suffer from non-use. As it nears the "dead" point, it will suffer a lot MORE.
    Eventually it will be so dead that it can't be charged and will be useless.

    The HV battery, OTOH, will generally tolerate non-use much better. Generally.
    But if there is a cell or two on the verge of going "bad", that trip might be completed during storage.
     
    Johnny Sasaki and Mendel Leisk like this.
  9. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,768
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    My point is however that IF the battery is failing, and this is maybe a very old 12 volt battery, if the OP's choice or question is can I wait to replace it?
    The answer is yes. They can wait to replace it.

    The OP should be aware, and I believe is aware of the deterioration process, which yes does mean non-usage is going to allow the battery to deteriorate further, but if the ultimate question or decision is to replace the battery, it doesn't matter much if it's a failing battery, perhaps capable of taking a charge, or if it's a completely dead battery. It's going to be replaced. In one scenario it might mean replacing it yourself in your driveway or jumping it to get it to the battery outlet, but the end result is going to be the same.

    If the OP is looking to salvage or continue to get function or life out of the existing battery? Then by all means, charge it up, see what happens.
    But otherwise my answer to the question " Is there harm in delaying replacement of the 12 volt battery" is No.
     
  10. frodoz737

    frodoz737 Top Wrench

    Joined:
    Aug 26, 2010
    4,272
    2,287
    33
    Location:
    Texas
    Vehicle:
    2015 Prius
    Model:
    Four
    Respects, but this is like putting off fixing a leaking tire. Just change your battery and move on. ;)
     
  11. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,768
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    But if someone asked you, during this crisis especially, Can I put my car up on blocks and wait to replace the tire? What would your answer be?

    I personally think, IF as the OP professes, they aren't going to be driving the vehicle much if at all for some extended period. just wait. I want to be able to usage test new purchases. I don't want to put a new battery in, or for that matter new tires on...then NOT be using the vehicle.
     
  12. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

    Joined:
    Oct 17, 2010
    42,046
    30,129
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    The debate can never be resolved, because both courses work?
     
  13. frodoz737

    frodoz737 Top Wrench

    Joined:
    Aug 26, 2010
    4,272
    2,287
    33
    Location:
    Texas
    Vehicle:
    2015 Prius
    Model:
    Four
    No...I would tell them to fix the leaking tire...just like I said change the battery. What is there to understand? If stuff breaks...fix it. Don't ask for permission or an excuse not to.
     
  14. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,768
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I agree..

    But the OP isn't asking for permission or excuse the OP is SPECIFICALLY asking
    " Is there harm in delaying replacement of 12v battery?" .
    The answer IMO to that question has to be NO..there is no harm.
    Whether You or I think it better to replace it immediately or not? Not the question.

    I personally, PERSONALLY wouldn't want to slap a new battery in a vehicle that was just immediately going sit and NOT be used.
    Too many stories of "bad" new batteries, or mistakes made in installation. You could slap a new battery in right now, and return in 6 weeks to discover it suddenly isn't working.
    So my recommendation also for those reasons is just wait, until you project the vehicle will be used more regularly or as before the crisis.

    If the question was Can I, or Should I replace the battery...my answer would be framed more like yours. But that isn't the question.
     
    2012 Prius v wagon 3 likes this.
  15. frodoz737

    frodoz737 Top Wrench

    Joined:
    Aug 26, 2010
    4,272
    2,287
    33
    Location:
    Texas
    Vehicle:
    2015 Prius
    Model:
    Four
    ...and I'm not going to further engage in "your" personal debate. End of line.
     
  16. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,768
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Wasn't meant to inflame or insult you and make you run away...
    Only clarifying what the question REALLY was, and why my answer was what it was.
     
  17. Johnny Sasaki

    Johnny Sasaki New Member

    Joined:
    May 4, 2020
    5
    0
    0
    Location:
    SF Bay Area
    Vehicle:
    2007 Prius
    Model:
    Base
    I see. I'm planning on replacing the 12v battery either way (given its age) and fortunately the expense of a new 12v isn't a big deal for me at this time. The expense of replacing the HV on the other hand...

    I didn't mean the stir up so much commotion in this thread -- my apologies. Our '07 Gen2 is a secondary car but in the current environment it sees use like a tertiary/quaternary car and we would really have to go out of our way to actually drive it more than once or twice a month.

    I'm leaning towards having the battery jumped in the next few days and having the car run in park/ready for about a half hour every week (if the 12v doesn't die by the next time I turn it on).
     
  18. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    5,131
    2,765
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    That is a viable course of action, but you might want to consider 60 once a week. In addition, if you have a battery charger, charge up the battery before starting this course of action.
     
    Johnny Sasaki likes this.
  19. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    4,529
    1,892
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    No need to apologize. It happens all the time.

    What you propose to do likely will NOT be a good plan.....because the onboard charging system was NOT designed to recharge a completely flat battery......and it won't come close just running for short periods like that.

    YOU NEED TO KEEP IT FULLY CHARGED after first getting it fully charged and that will NOT happen doing what you propose.
    Leaving it low on charge will cause it to deteriorate even more.......even if it does barely start on it's own.

    I think this has been said before in this thread. It needs to sink IN.
     
  20. Johnny Sasaki

    Johnny Sasaki New Member

    Joined:
    May 4, 2020
    5
    0
    0
    Location:
    SF Bay Area
    Vehicle:
    2007 Prius
    Model:
    Base
    Sorry for being dense -- is a 12V battery tender a way to accomplish that?

    Unfortunately my garage is a detached carport and there's no way to get an electrical outlet near the car -- is long-term storage of the car not viable otherwise? How about just disconnecting the negative terminal from the battery and reconnecting it once every 1-2 months for a 30-minute drive?
     
Loading...