Welcome to PriusChat

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

Sign Up

Big battery concerns

Discussion in 'Gen II Prius Technical Discussion' started by IABoy987, Mar 7, 2012.

Social Buttons

  1. IABoy987

    IABoy987 Junior Member

    Joined:
    Nov 25, 2011
    Messages:
    34
    Likes Received:
    1
    Location:
    Iowa
    Your Vehicle Year:
    2011 Prius
    Model:
    Four
    Noticed for second time that the battery indicator was down to one purple bar. Car still started but seemed it was the ICE that was doing the work and the motor helping out now and then. Prius is used to drive to/from work (10-15 minutes) and sits rest of time. Most times display is green bars or mostly blue ones. Have noticed the MPG is getting crappier and crappier (35-40MPG) as though the ICE is on line most of time.

    Is this a concern that I should take it to Toyota for look see? Is this indication of a cell or two becoming reversed charged? Any combination of buttons and/or switches that will "magically" allow me to see on display whats really going on with big battery? I would rather spring for a new rebuild than be stranded "on a dark and stormy night".
  2. efusco

    efusco Troll Slayer Staff Member

    Joined:
    Nov 26, 2003
    Messages:
    19,849
    Likes Received:
    1,079
    Location:
    Nixa, MO
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    Could you please describe the problem a bit more.
    When did it start? Is it just occasionally going down to 1 bar or is at one bar and never comes up any more?
    Has anything about your usual commute changed?
    How many miles have you driven while this has been going on?
  3. JimboPalmer

    JimboPalmer Nadir of Wrongness

    Joined:
    Apr 14, 2009
    Messages:
    8,005
    Likes Received:
    2,440
    Location:
    Greenwood MS USA
    Your Vehicle Year:
    2012 Prius v wagon
    Model:
    Three
    Many, if not most, issues with the HV battery will cause a Check Engine Light and generate codes that the Techs can read.

    As a diversion, how many years are on the 12 volt battery? Some failure modes will cause the 12 volt battery to appear to need recharging constantly (when READY) That will reduce MPG and be a drain on the HV battery.
  4. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    Messages:
    18,046
    Likes Received:
    2,955
    Location:
    Northern Michigan
    Your Vehicle Year:
    2006 Prius
    What is your weather like? Have you experienced colder weather recently?

    Tom
  5. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    Messages:
    3,326
    Likes Received:
    1,438
    Location:
    Santa Fe, NM
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A
    A reversed cell would definitely trigger a fault code.

    A dealer trip for an HV battery check without codes is usually a waste of time and money.

    The 12V would be the place to start.
  6. miscrms

    miscrms Plug Envious Member

    Joined:
    Aug 21, 2007
    Messages:
    1,986
    Likes Received:
    472
    Location:
    Phoenix, AZ
    Your Vehicle Year:
    2005 Prius
    Checking the 12V battery sounds like a good idea. If its old (more than 3 years) you might just go ahead and replace it. The 12V is recharged from the HV battery so if its failing and drawing current from the HV that can do what you describe. 12V battery issues can cause all kinds of strange behavior and mimic more serious failures including false warning lights and codes.

    The management system on the HV battery looks at the voltages within the HV battery and is pretty quick to throw the big red triangle and generate codes if anything is out of whack. In the days/weeks preceding that you might see the battery display moving up and down from near empty to near or completely full far faster than seems normal/reasonable. Even if you do suspect HV battery issues the 12V is a good place to start.
  7. andyprius

    andyprius Senior Member

    Joined:
    Feb 21, 2005
    Messages:
    2,212
    Likes Received:
    162
    Location:
    Sacramento, California.
    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Have you tried to force charge the HV to Green Bars? If you can do that, probably the HV Bat is OK.
  8. jadziasman

    jadziasman 72K miles to go before the odometer stops

    Joined:
    Jan 17, 2011
    Messages:
    719
    Likes Received:
    188
    Location:
    District 6
    Your Vehicle Year:
    2005 Prius
    Model:
    Five
    MG1 provides the electricity to recharge both the traction battery and the 12V auxilliary battery - while the Prius is moving forward at most speeds anyway since the ICE is doing most of (if not all of) the work. MG1 draws HV traction battery power only when starting the engine. The traction battery definitely does not charge the 12V aux battery - directly or indirectly.

    MG1 can juice up that little 12V aux battery all day and all night and not even notice it's there. The 200+ Volt HV traction battery is what sucks up most of the juice. MG1's main job is recharging the traction battery.

    You know, I remember way back in 2010 when I drove a car equipped with something called an alternator. The alternator was this tiny belt-driven generator that could power all of the car's electrical systems and recharge its somewhat large 12V battery at the same time. Amazing really.

    Now, if it's really the traction battery that is dying, then you'll find the ICE running all day in a futile attempt to recharge it.

    The 12V aux battery will be just fine since it needs so little juice in comparison to its big brother. And even if the 12V battery was near the end of its useful life, it still wouldn't put a strain on the engine and MG1.
  9. andyprius

    andyprius Senior Member

    Joined:
    Feb 21, 2005
    Messages:
    2,212
    Likes Received:
    162
    Location:
    Sacramento, California.
    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base


    I was actually speaking to the OP You have written a nice little ramble, but none of it addresses the OPs concern.
  10. jadziasman

    jadziasman 72K miles to go before the odometer stops

    Joined:
    Jan 17, 2011
    Messages:
    719
    Likes Received:
    188
    Location:
    District 6
    Your Vehicle Year:
    2005 Prius
    Model:
    Five
    You know, andy, I wasn't responding to what you wrote. If I had, I might have started with the post by writing, oh let's see...... andy.

    If you don't like what I have to add, then don't bother reading it, let alone taking the time to comment on it.

    The OP has a legitimate concern about the HV battery. He is also being given, IMHO, bogus advice by some people. And if it turns out that I'm incorrect about what I wrote - it won't be the first or last time.
  11. andyprius

    andyprius Senior Member

    Joined:
    Feb 21, 2005
    Messages:
    2,212
    Likes Received:
    162
    Location:
    Sacramento, California.
    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base


    Sorry, I assumed you were, that is the problem with Priuschat replies coming direct thru my Email. All post actually address to me. Again a gross false assumption. ON MY PART :(:(
  12. DeadPhish

    DeadPhish Senior Member

    Joined:
    Sep 10, 2005
    Messages:
    2,006
    Likes Received:
    351
    Location:
    Outer Banks of NC.. Retired to play golf and poker
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A
    I'm now at 208,000 miles. Last week for the first time I got a check engine indicator that popped on out of the blue. It was in mid trip during an 11 hr RT to central NC. The light stayed on for the entire trip back.

    I didn't drive it the next day but on the following I went out and the indicator was gone. Never happened :confused:.

    I've noticed that recently after my big 200K maintenance that fuel economy has dropped into the low-mid 40s iso 47 mpg lifetime. I recognize that it's winter and my usage is entirely different now than when I was working; now it's mostly short trips with a few 2 hr trips a couple of times a week.

    The 12v battery was replaced at 105K miles so that might need replacing again. I'm doing some preliminary investigation on used HV batteries just in case. I just saw the first Prius c in the area yesterday. Prolly too small.
  13. IABoy987

    IABoy987 Junior Member

    Joined:
    Nov 25, 2011
    Messages:
    34
    Likes Received:
    1
    Location:
    Iowa
    Your Vehicle Year:
    2011 Prius
    Model:
    Four
    Hmm, for some reason, the forum did not notify me of replies to my query.

    Anyway to answer questions posed here as best as I remember:
    1 I live in Iowa and we are having the warmest winter ever according to forecasters. Don't know if this affects the MPG. Tires inflated to about 40lbs each per instructions.

    2 The car is at 79K+ miles at this point, and about 5 years of ownership (brand new with me) with only one new set of tires and regular oil, fluid, air filter etc maintenance ("knock on wood" that engine does not fall off its mounts:eek:).

    3 Did a check small battery with holding Info button and turning headlights on/off 3 times. Little battery is at 11.5V which the instruction says is not good. So will call Toyota for bad news of how much it cost to replace it.

    4 Now have full set of green bars when I started it up this morning, but last night screen was all white except for one lonely purple bar at bottom, just like a previous time.

    And finally, a BIG thank you to all who replied to my question. Much appreciated.:)
  14. efusco

    efusco Troll Slayer Staff Member

    Joined:
    Nov 26, 2003
    Messages:
    19,849
    Likes Received:
    1,079
    Location:
    Nixa, MO
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    The 12v is probably the problem in a 5 year old car still on the original.
    I'm still not clear what you're seeing on the Energy screen during normal driving, however. If you're seeing wide dramatic swings b/w 1 purple bar and 8 green bars that you've never seen before, that could be an early sign that your Traction battery is bad--even if you haven't had any warning lights yet. If you're just seeing mostly normal, but occassional drops to purple and occasional increases to 7 green, then that's probably normal.
  15. JimboPalmer

    JimboPalmer Nadir of Wrongness

    Joined:
    Apr 14, 2009
    Messages:
    8,005
    Likes Received:
    2,440
    Location:
    Greenwood MS USA
    Your Vehicle Year:
    2012 Prius v wagon
    Model:
    Three


    Not a cheaper battery, but a better one.

    Optima DS46B24R Optima battery direct fit replacement for Prius 2004 +
  16. JimboPalmer

    JimboPalmer Nadir of Wrongness

    Joined:
    Apr 14, 2009
    Messages:
    8,005
    Likes Received:
    2,440
    Location:
    Greenwood MS USA
    Your Vehicle Year:
    2012 Prius v wagon
    Model:
    Three


    You are at a traffic light, ICE is at 0 RPMs, MG2 is at 0 RPMs, MG1 HAS to also be at 0 RPMs, yet the inverter is producing 13.8 volts from somewhere. I think you are wrong.



    When the 12 volt battery is operating normally, true. But, as an example, consider one cell shorted out. This battery can't charge past 10 volts with 5 good cells, so MG1 will drop a lot of power on it trying to get it over 12 Volts. All of that energy is not helping MPGs, so they go down.

    We do not get that slow sluggish starter noise in a Prius to remind us that our 12 volt battery is on its last legs. This does not mean it is not on its last legs. I do not think the 12 volt battery in a Prius is all that bad, but I do think it can sneak up on us better than other cars.
    1 person likes this.
  17. andyprius

    andyprius Senior Member

    Joined:
    Feb 21, 2005
    Messages:
    2,212
    Likes Received:
    162
    Location:
    Sacramento, California.
    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base


    Interesting that this very first post pointed exactly to the 12V Battery, but the OP stressed problems with the HV Battery alluding to a serious problem. This is / was a failing 12V Bat, not addressed, not looked into, not measured and no attempt to pinpoint the problem. ie: stressed causing low output, 1 bad cell, poor connection, etc. We have for years now emphasized the importance of the 12 V Battery, ad nauseum. Also interesting is that apparently these batteries can be rejuvinated just by charging separately on a bench and adding a small amount of distilled water to each cell as needed. I think the standard question, with these and other symptoms is "" HOW'S THE 12V ? "" Does any new poster use the very rich archives ???? :cheer2:
    2 people like this.
  18. efusco

    efusco Troll Slayer Staff Member

    Joined:
    Nov 26, 2003
    Messages:
    19,849
    Likes Received:
    1,079
    Location:
    Nixa, MO
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A


    That is not correct. There is a DC-DC inverter and even with MG1 at 0 RPM the traction battery charges the 12v via that inverter.
    1 person likes this.
  19. jadziasman

    jadziasman 72K miles to go before the odometer stops

    Joined:
    Jan 17, 2011
    Messages:
    719
    Likes Received:
    188
    Location:
    District 6
    Your Vehicle Year:
    2005 Prius
    Model:
    Five
    Okay aux battery worshippers! I surrender. It seems it's impossible to free you from your unshakable faith in the omnipotence of your beloved. Hey, you've something to believe in! I'm happy for you. I won't ever question your faith again even though I am a heretic in this regard.

    All right, I confess that I was technically incorrect in stating that the traction battery never charges the aux battery when the Prius is not in motion. That in and of itself is not a serious misjudgment in the big hybrid picture though. Ultimately it's still the ICE that charges the aux battery, not the traction battery. I spend most of the time in my Prius driving at a serene 70 mph. Not a lot of serious traffic jams here in my neck of the woods.

    Sure, the aux battery is being supplied with 14V from the DC/DC converter while the other electrical systems are being supplied with power from the traction battery at the same time. I just don't consider this as the traction battery charging the aux battery. From what I can see from the wiring diagram, the aux battery isn't doing anything at this point and it shouldn't be. It's the traction battery that needs the constant replenishment from the ICE via MG1 and MG2. The traction battery is providing power to the ECUs, the headlights, the radio, the AC, the heater, etc while the car is standing still and in the READY mode. The aux battery is on standby at this point. And when the SOC reaches a certain point, presto the ICE automatically fires up again. A worn out traction battery is the real problem for the HSD while in READY mode, the aux battery has no active role to play.

    Correct me if I'm wrong - I know someone will speak up. Please tell me what, if anything, the aux battery is supplying power to when the Prius is in READY mode. Or why it would draw a lot of power when having nothing to do.

    And if the aux battery is near the end of its life, it just won't be able to start the HSD reliably. And if, for whatever reason, it was possible to start the hybrid systems with a weak aux battery, well, the worst outcome from that would be that the ICE would run more often but I can't see how that half pint aux battery can be so demanding as to upset the apple cart. Makes no sense because where is the electric load on the aux battery at this time when the HSD is running other systems. Sure the aux battery has internal resistance but is it enough to cause the havoc that have sent so many of you into a tizzy?

    My '05 has 166,700 miles, turns 7 years old this month, and STILL has the original aux battery that was installed at the factory in Japan. I've owned many cars in the past 36 years and I can't remember a 12V battery lasting that long in any of my non-hybrid cars. That tells me the Prius aux battery has a limited, easy job to do. I will replace it only when it needs replacement and that will be just like any other car, I'll know it's shot if it needs to be jump started (which I'll be afraid to do when the time comes).

    I have had no problems at all with my '05 after the 33K miles I've driven it thus far and have never experienced any of the bizarre behaviors that many swear up and down must be caused by that pesky aux battery. The power door locks work every time, the interior lights seem to shine brightly, etc. I don't see any issues with the OEM aux battery whatsoever.

    The Optima company must ADORE Priuschat because of all the unnecessary 12V battery replacements that they have sold the past few years since the early adopters have sent out their clarion calls to Prius owners everywhere. Some even claim that the OEM battery is garbage. Again, that's great publicity for the Optima people they just can't buy.

    I have never, ever heard of anyone (until now) replacing a perfectly sound 12V OEM battery as a preemptive strike against the unfathomable possibility of being stranded by a dead battery - GASP! What is this world coming to????

    If you wanna go and take a ride wit me
    We three-wheelin in the fo' with the gold D's
    Oh why do I live this way? (Hey, must be the money!)

    I enjoy Priuschat and visit it every day.:)
    1 person likes this.
  20. JimboPalmer

    JimboPalmer Nadir of Wrongness

    Joined:
    Apr 14, 2009
    Messages:
    8,005
    Likes Received:
    2,440
    Location:
    Greenwood MS USA
    Your Vehicle Year:
    2012 Prius v wagon
    Model:
    Three
    Fact 1) Almost all of us know when a 12 volt battery is dead because the starter makes that slow grinding noise. This will never happen on a Prius as the 12 volt battery does not power the 'starter' MG1.

    Fact 2) Related to the above, most 12 volt batteries are deemed dead when they lack the Cold Cranking Amps to start the engine. The Prius never needs a huge surge of Amps to start, so the battery fails in other ways.

    My Opinion: Many folks misdiagnose 12 volt battery problems as something else, as the 12 volt battery gave no familiar warning signs it was in ill health. Reminding folks to do a free and simple test before spending over a $1000 on even a used HV Battery is a wise piece of advice. Will it always be right? NO, (Will it always be free? YES)

    Fact 3) Unfortunately, Toyota has no polarity protection in a Prius. Each time you jump a Prius 12 volt battery you risk a multi thousand dollar repair if you get the cables backward. I am paranoid enough I bought jumper cables that have polarity protection. Not everyone does. http://priuschat.com/forums/gen-ii-prius-main-forum/104431-boosting-mishap.html
    2 people like this.
Similar Threads: battery concerns
Forum Title Date
Newbie Forum Concerns before buying Used 2008: Winter-driving and Battery Dec 1, 2013
Newbie Forum New but older year model prius: battery concerns? Sep 25, 2013
Newbie Forum Battery life - concerns? Sep 4, 2013
Generation 1 Prius Discussion 2003 Battery Concerns Aug 30, 2013
Prius v Main Forum 2012 Leftover Prius v Five - any concerns about battery cells degredation? Aug 12, 2013