Welcome to PriusChat

We'd love to have you join our community and participate in the conversation! Sign up for FREE today.

Sign Up

Gen I 12V battery charging

Discussion in 'Newbie Forum' started by flynham, Dec 16, 2010.

Social Buttons

  1. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A
    I just purchased this 2001 Prius. The hybrid battery pack was totally discharged. I replaced the battery pack along with several fuses. The car started and ran fine. After a day or so I started the car and drove it a few miles. As I was driving, "check engine" display came one. Shortly thereafter, at a stop, the car "died". After some checking, I put a booster on the 12V battery and drove it home. As I was driving it the "check engine" display was still on. What should I look for to determine the problem with this car?
  2. drew_flux

    drew_flux Junior Member

    Joined:
    Jun 24, 2009
    Messages:
    73
    Likes Received:
    20
    Location:
    sydney australia
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    it sounds like your aux battery is not holding charge.however there may be other issues going on. i would 1. loadtest/charge the 12v battery.if thats ok then 2.check the charge rate coming from the inverter.put a voltmeter across the aux battery with ready on, you should have 13-13.8v on the meter.
  3. drew_flux

    drew_flux Junior Member

    Joined:
    Jun 24, 2009
    Messages:
    73
    Likes Received:
    20
    Location:
    sydney australia
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    oh just remembered when chargeing the aux battery with a charger. do not let the charge current rise above 4.5 amps.
  4. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A


    Thanks a bunch. I will try that tomorrow to see what happens. Have
    the 12V battery on trickle (2 amp) charge right now so should be good
    tomorrow. If the voltage from the inverter is not as you mentioned,
    does this mean the inverter is malfunctioning?
  5. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A
    Checked the voltage this morning and it is showing 12.12V with the "ready" on. Could anyone tell me where to go from here? From what I understand, the 12V battery is NOT being charged from the inverter. Does this mean the inverter is bad or is there something other than the inverter that would cause this problem? Thanks
  6. drew_flux

    drew_flux Junior Member

    Joined:
    Jun 24, 2009
    Messages:
    73
    Likes Received:
    20
    Location:
    sydney australia
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    I just realized that you had a gen 1,i was thinking you had gen 2, i may have given you some bad info, will look in to the charging system on gen 1 on Monday. i seem to remember the gen 1 having a normal starter motor, now I'm wondering if gen 1 has a normal alternator as well and i have just forgotten.its been a while since i worked on one.
  7. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A


    Thanks much! I'll be waiting to hear from you....
  8. drew_flux

    drew_flux Junior Member

    Joined:
    Jun 24, 2009
    Messages:
    73
    Likes Received:
    20
    Location:
    sydney australia
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    thinking a bit more clearly today. don't know where i got the idea the was a normal starter motor on a gen 1. must be time to stop forum surfing late at night lol . Gen 1 prius definitely charges to aux battery through the inverter's dc-dc converter. been through the repair manual for nhw11, this morning, still can not find a spec for the charge rate.can only give you the numbers that i can test on vehicles coming through the work shop. your reading of 12.2 still seem a bit low when compaired to other vehicles, that have been coming through the workshop. i wonder if your 12v battery is any good.have your had it load tested?
  9. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A


    Have not had it load tested. Will do that first think in the morning.
    It is a relatively new battery, but from past experience, that doesn't
    mean a whole lot. After I have it tested I will let you know what I
    come up with. Again, thanks so much for your help.
    Emmette
  10. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A
    12V battery checks good, so will search other areas....
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    Messages:
    13,397
    Likes Received:
    3,204
    Location:
    Green Valley, AZ
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A


    You are right, the DC/DC converter within the inverter is not working correctly, since the voltage should be ~13.8VDC when the Prius is READY.

    You may want to obtain the logged DTC to confirm that the inverter has failed.
  12. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A
    Eventually got a code which referred me to either the ECM or HV ECU. From all I can
    deduce, the HV ECU is malfunctioning but will be replacing it and the ECM just for good
    measure. Thanks so much to drew_flux and Patrick Wong for the help. Will get back with you to let you know the results as soon as I get both computers replaced.
  13. flynham

    flynham New Member

    Joined:
    Dec 16, 2010
    Messages:
    8
    Likes Received:
    0
    Location:
    Northwest Florida
    Your Vehicle Year:
    2001 Prius
    Model:
    N/A
    For anyone chasing this thread, the end result was that my ECM was faulty in the car.
    After changing it, everything worked fine with voltage to Aux battery now at 13.8 with the
    "Ready" light on. Hopefully this might help someone else that encounters the same problem.
Similar Threads: battery charging
Forum Title Date
Gen II Prius Care, Maintenance and Troubleshooting Battery Discharging when lights are on Oct 20, 2014
Toyota Prius Plug-in 12V Battery near-dead after charging HV battery :-( Oct 17, 2014
Gen II Prius Technical Discussion Prius MFD not showing the battery charging Oct 12, 2014
Gen II Prius Care, Maintenance and Troubleshooting Help! Battery only charging downhill and braking Sep 19, 2014
Gen II Prius Main Forum Charging and discharging traction battery Aug 1, 2014