HELP! Prius 2010 does not start with a new aux battery

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Mykola2022, Jul 4, 2022.

  1. Mykola2022

    Mykola2022 New Member

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    I bought a used 2010 Prius a couple months ago. My wife was driving it, when she saw a message on the screen saying something about the Hybrid battery, according to her. Message disappeared in a few seconds, so I do not know what it was exactly.

    Next day, she could not start the car. And all its electrical circuits were dead, lights and doorlocks did not work. So, I concluded that the problem was with the aux battery. I measured its voltage. It was about 1V when connected, and about 8V when disconnected.

    I bought a new battery at Autozone, which they recommended
    Duralast Platinum AGM Battery 46B24R-AGM
    I installed it, but could not start the car. Voltage was 2V when connected, and about 13 when disconnected.

    I jump started the Prius, drove it for 30 min, and left it parked in ready mode overnight, for 8 hrs total in ready mode. Voltage was increasing while it was charging. I was surprised to see 40V, but I do not know what it should be while it is charging from the Hybrid battery.

    After 8 hrs of charging, I pressed the power button to turn it off, and immediately tried starting it. The car does not start again, its lights and locks are not working, as if the battery is dead. Voltage is about 14V, which should be enough to start it.

    I checked the fuses related to power, all of them are good.

    Could this indicate an issue with wiring or something? Or is this battery not suitable? I have no idea where to look next.
     
  2. CR94

    CR94 Senior Member

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    Maybe a loose or corroded connection somewhere? Where were you measuring the voltage? I hope the 2v from a new battery, and the 40V are typos, because neither makes any sense.
     
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  3. JC91006

    JC91006 Senior Member

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    When the battery is new and not connected, it should read around 12v - 13v. If this battery had that reading when new, then it shouldn't have any issues starting the car when it's connected. A fully charged battery should be around 12.7v-12.9v when it's connected

    When the car is in READY mode, the battery voltage should be around 14.1v. It should not read above that voltage, even after 10 hours of leaving it in READY mode.

    Your battery readings are all over the place, a new battery should not have that big of fluctuations. I would check to make sure all your connections are tight
     
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  4. PriusCamper

    PriusCamper Senior Member

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    Sounds like a bad 12v... What's the voltage reading on it when the car is off?

    This is the one that is highest quality for lowest price in my opinion: https://ebay.us/5n8222

    I can explain batter terminal for it if you decided to go with this option.
     
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  5. Mykola2022

    Mykola2022 New Member

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    Maybe, that was mistake about 40V, because I was measuring at night, but let us focus on its current condition.

    If I disconnect one of the wires and measure voltage between the wire and the terminal, I get about 15V for both + and - side. I just tightened all connections to make sure they are not the issue. Right now I get about 14V between battery terminals.The analog voltmeter I have is not very presice, I have to choose 50V scale, but these numbers are consistently in 14-15V range. It seems like the circuit is powered, but none of the electronics are working.
     
    #5 Mykola2022, Jul 4, 2022
    Last edited: Jul 4, 2022
  6. Mykola2022

    Mykola2022 New Member

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    Update.

    After the last ride, just before the old battery died, we were able to lock the car with the remote key, which probably means that the wiring and fuses are ok. I just tried reinstalling the old battery and jump starting it, in order to see if it may have some residual capacity to do anything after the car power will be turned off. Jump start did not work at all.

    Then I checked the new battery, which was sitting there for 9 hrs since it was fully charged overnight. Voltage was below 10 when connected. Jump started almost momentarily, will let it charge a little more and see if it will do anything.

    Out of curiousity, I checked the voltage on the jump wires, which were connected to the 12V battery terminals under the back seat of my donor car running (Prius C). It was about 40V. I started the acceptor car, so that it charges its battery itself now. And the wires, connected to the battery also read about 40V. So, I guess it is not a mistake. The battery is being charged by the running car at 40V. Do not get it wrong it does not produce 40V, it consumes 40V in order to get charged.
     
    #6 Mykola2022, Jul 4, 2022
    Last edited: Jul 4, 2022
  7. bisco

    bisco cookie crumbler

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    are you checking with the car 'ready'? if so, that is the inverter charging voltage.

    you should check the voltage at the battery and at the jump point under the hood after the car has been off a few hours.

    that will also tell you if there is a wiring problem.
     
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  8. Mykola2022

    Mykola2022 New Member

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    I was getting 14-15V at the battery after the battery was charged for a few hrs, and right after I turned off the car, and could not start it again. Have not tried the jump point yet. Will do that next. Thanks!
     
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  9. Mykola2022

    Mykola2022 New Member

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    I just charged the battery for over an hour, turned power off, and the car immediately died as usually, display went dark in a moment. Voltage between the battery terminals is about 13V, and about 12V at the jump point. I will check it again later.
     
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  10. JC91006

    JC91006 Senior Member

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    You may have a defective battery or you have defective equipment reading the battery voltage.

    If you are charging the battery, the car battery (agm) is designed to be charged using 4 amps to 10 amps only. No high powered 20 amp or higher chargers
     
  11. Mykola2022

    Mykola2022 New Member

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    Two hours after the battery was charged, I am getting 9V between battery terminals, and about 8.5V at the jump point.

    The results were consistent, when I repeated the measurments. And same happened this morning, as I mentioned above. After 8 hrs of charging, it was about 14V, but it dropped to 9V by the end of the day. I should probably return this battery and get something else.
     
  12. rjparker

    rjparker Tu Humilde Sirviente

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    Your meter is bad. Buy a digital meter.

    Not likely unless the car had a direct positive to negative short. You would get sparks like an arc welder.

    This is an invalid test. You can't accurately measure voltage with a meter in series to the circuit.

    ----

    However, you could have an excessive parasitic draw running down the 12v battery. To check that you insert an amp meter in series (not a voltmeter which is a separate instrument in your old school world of analog meters). A parasitic test checks amp draw when the car is off. It should be less than 30 ma. A hatch light left on will drain the battery overnight. Other parasitic drains can be worse. I would not attempt this test without help.

    The fact you have jumped it successfully a couple of times says all you need is a charged battery. Do not repeat the overnight Ready trick. Not good at all. What if the car overheated? Burned up engine.

    You need a Battery Tender Jr, about $35 at Walmart or Amazon to charge the battery overnight.

    But the FIRST thing you should do is take the battery back to the supplier and have them do a "Load Test" on the battery. Also have them charge it up. Usually free. I would suggest finding a mechanic or a friend to help you with this problem based on the steps taken so far.
     
    #12 rjparker, Jul 5, 2022
    Last edited: Jul 5, 2022
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  13. rjparker

    rjparker Tu Humilde Sirviente

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    I hate to muddy the water (well maybe not), but bad things happen if the car is jumped with reversed polarity. Meaning the plus on one car is hooked to the minus on the other. Even for a second.

    At that point the car won't go to Ready and many things are not powered up anymore including everything served by the driver's side interior fuse box. For example the interior lights.

    An inadvertent reversed polarity jump will blow the 125 amp fusible link buried inside the driver's side engine fuse box. A few more fuses in that box will also blow. Getting to the 125 amp fusible link requires removal of the engine fuse box, a difficult task.

    There is a small visual access port that can be checked to see if the 125 amp is blown. Use a flashlight. Again if the interior lights work, you are ok. Obviously a discharged battery can also kill lots of things including the interior lights.

    All of which is the reason to avoid jumping the Prius especially with another car. A lithium jump box like the Noco GD40 (an ultrasafe polarity checking jump pack $100) is the way to go.

    Finally, while reverse polarity jumps have taken out many 125 amp fusible links and other more accessible fuses, "usually" the vehicle is otherwise undamaged by some miracle of Toyota engineering. In your case hopefully a blown 125 amp is not the problem. Get your new battery checked.

    Visual of 125 amp fusible link (fuse):

    * 125a fuse visible from top.jpg
     
    #13 rjparker, Jul 5, 2022
    Last edited: Jul 5, 2022
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  14. nicoj36

    nicoj36 Member

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    Sure its not your remote-key's battery? The car simply doesn't detect the key hence the no-start? Also, get optima battery or oem toyota from dealer.
     
  15. bisco

    bisco cookie crumbler

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    sounds defective. a load test at the place of purchase will confirm it
     
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  16. Mykola2022

    Mykola2022 New Member

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    I took the battery back to the Autozone and requested a load test. It proved a defective battery. They gave me a replacement, which they also load-tested. The car started working as I was installing the battery.

    Also, I agree, that my old analog voltmeter is not showing correct voltage. It is consistent, but not correct )))

    Sorry, that I raised this topic. I could never imagine that Autozone would sell me a dead battery, so I was thinking that the car was having other issues as well.
     
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  17. rjparker

    rjparker Tu Humilde Sirviente

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    Autozone is the bottom of the barrel auto supply. Their corporate management has no desire to be good. Go elsewhere.

    This is a decent meter for $37. It includes a dc amp clamp which is rare under $300. I would also buy a $5 "beater" digital meter at Harbor Freight which actually is decent for series parasitic testing and around the house quick checks.

     
  18. jzchen

    jzchen Senior Member

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    Technically the battery label says 4.2 A max +/- 0.1A if I recall correctly...

    REVVL V+ 5G ?
     
  19. ASRDogman

    ASRDogman Senior Member

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    I don't think autozone sold you a known defective battery. It happens.
    I've worked at various dealerships and have come across defective parts.

    If you think of the probably hundreds of thousands of each part they make, sooner
    or later some won't be up to par. That's why there are warranties!

    Did you check the voltage of the replacement battery? And it still may need to be charged.
    2 weeks ago I replaced my battery. It was at 11.9 volts, right from Toyota. I kinda expected it.
    And of course it didn't have enough juice to get the electronics up and running. I put it on a 3 amp
    charger for about 3.5 hours. It was enough to get it going. Then drove for an hour. It sat for 3 hours.
    And started right up. After I got home I put it on the charger for 10 hours. Haven't had a problem since.

    You volt meter may be fine. Hard to judge it against a bad battery. Harbor frieght sells the cheapest of
    the cheapest chinese junk. It's "good enough" for simple things. Don't expect it to last.

    Autozone sells junk too, but they also have the better stuff. It will just cost more.

    Sadly, almost every place is having there stuff made in china....

     
  20. rjparker

    rjparker Tu Humilde Sirviente

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    That rule is for unregulated chargers. Staged chargers including the car can go 60-80 amps for short periods.
     
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