Prius sat for 4 months, battery is dead - how to restart?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dipstick22, Mar 2, 2025 at 4:29 AM.

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  1. dipstick22

    dipstick22 Junior Member

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    The backstory is a divorce and a neglected 2008 Prius with just under 300,000 miles. The 12-volt battery is now completely dead. The car was starting to have intermittent problems while driving (VSC coming on under normal conditions). My first question is whether it is worth even buying a new $250 battery only to find out that the car is beyond repair. I have a friend with a Gen2 and was thinking of asking if I could "borrow" his battery to see what happens when I put it in and try to start up. Do I need to do anything special when I put the battery (new or borrowed) in the car?

    Second question - how can I find someone (other than the Toyota dealer) who works on Prius' in central Delaware?
     
    #1 dipstick22, Mar 2, 2025 at 4:29 AM
  2. MAX2

    MAX2 Active Member

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    Without a 12V battery you will not be able to start the Prius properly, so this is the first thing you need to do.


    If errors appear, then you need to diagnose the systems.
     
    #2 MAX2, Mar 2, 2025 at 6:03 AM
  3. dipstick22

    dipstick22 Junior Member

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    Thanks. I was concerned that I would be required to go through some kind of extensive "setup procedure". Hopefully the factory default settings for things will take over.
     
    #3 dipstick22, Mar 2, 2025 at 8:19 AM
  4. MAX2

    MAX2 Active Member

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    Have you used this hybrid before?

    When the car is standing still for a long time, problems can appear in different places. If something goes wrong, you can contact the forum for help.
     
    #4 MAX2, Mar 2, 2025 at 8:26 AM
  5. JC91006

    JC91006 Senior Member

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    You can simply jump start the car and see if there are other problems, it should be able to run but might give you a battery error. Chances are your big HV battery will probably have issues as well (depending on the age of that battery)
     
    #5 JC91006, Mar 2, 2025 at 9:46 AM
  6. dipstick22

    dipstick22 Junior Member

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    MAX2 & JC91006 - We are the original owners of the car since 2008. I know it "like the back of my hand". At about 295,000 miles, we loaned it our son-in-law and it was running fine. Then came the affair and separation and divorce. We took the car back but he said it had been "acting strange". I drove for a few weeks and saw 2 occurrences of the VSC kicking in for no reason under normal driving conditions. But it never threw a code. The hybrid battery was replaced at 190,000 miles and is not coding. For a variety of reasons, the Prius sat idle for about 6 weeks and when I tried to start it, the 12V battery was dead beyond recharge. From other responses, it sounds like installing a working battery would not require any special actions. So I'm heading down that path. I have a friend who also has a Gen 2 Prius. I think I'm going to ask him to let me "borrow" his battery to see if my Prius starts up and runs. If it does, I'll buy a new battery and give it to him.
     
    #6 dipstick22, Mar 2, 2025 at 12:01 PM
  7. JC91006

    JC91006 Senior Member

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    Just go to costco and buy a battery for $200. The installation is simple and it should fix your car. If you have the time to remove and install a friend's battery, you should just install a new one for $200 and call it a day. VSC will flash if you run over uneven pavement, it is a normal characteristic of this car.
     
    #7 JC91006, Mar 2, 2025 at 12:04 PM
  8. BiomedO1

    BiomedO1 Senior Member

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    IMHO; just jump start it - rather than play musical battery swap or replace it. The car will run strange for a few hours or days, while the sensors recalibrate themselves, due to the battery issue and lost ECU settings. You may even get a few phantom errors. Erase them and see if they come back after you've make sure the battery issue has been solved.

    Hope this helps....
     
    #8 BiomedO1, Mar 2, 2025 at 1:36 PM
  9. Dion Kraft

    Dion Kraft Member

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    I had my 2004 Prius sit for 3 years and the 12 volt battery even with trickle charge eventually became very weak. But anyways I bought a AGM battery from Autozone - they have two versions..one for non-smartkey and one with smartkey. But upon getting it started I encountered some faults like error display but repeat starts cleared that up as well as a little test drive helped. I lost the use of my Smartkey totally so I had to reprogram them but that was easy for Smartkey cars not like the non-smartkey where you have to go through the "Chicken dance" routine. But if you borrow your friends battery..it will not hurt his car so that may be the bargain option if your not sure as to what condition your car turned into. Its a gamble but its your call - Good Luck !
     
    #9 Dion Kraft, Mar 2, 2025 at 4:57 PM
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