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How is the 12 volt battery charged on the PIP

Discussion in 'Toyota Prius Plug-in' started by LenP, Mar 23, 2012.

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  1. LenP

    LenP Member

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    How is the 12-volt battery charged on the PIP? Is it only charged when the HV system runs, or does it also charge when the traction battery is charging from the wall? I've noticed at start up when the PIP is in EV mode the ICE starts spontaneously on occasion, even with the heat and AC both off. The traction battery has a good charge, so it needs to do this for some reason, but why? Is the 12-volt system running low? I drive almost totally in EV mode, so am I running the 12 volt system down? (TOYOTA some answers please)......and by the way the PIP is a dream EV 99% of the time. :D
  2. JimboPalmer

    JimboPalmer Nadir of Wrongness

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    I doubt you will ever see an official Toyota answer here, their US marketing group hangs out here, but the engineers tend to speak Japanese. I will offer SWAG* opinions while we wait for facts.

    Based on all recent Prius, the 12 volt battery charges from the inverter any time the car is in READY mode. It is possible that it also charges when on line voltage, a Scangage could tell you the voltage when charging.

    The PIP battery is still very small compared to the Volt/Leaf batteries, so there will be times the ICE is needed even when you have available range. Also, the logic going down slopes to conserve friction brake life may still apply, spin the ICE with no fuel to act as a 'jake brake'.

    It would be a minor 'bug' if it charges on line current to a such a full state that needs to 'burn' battery charge so it can use regenerative braking.

    Now we can wait and see if those with better facts can replace my mere opinion.

    *Silly, Wild Ass Guess
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  3. ryogajyc

    ryogajyc Active Member

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    Maybe you are hitting this condition from pg. 41 in the Owner's Manual:



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  4. Allannde

    Allannde Just a Senior

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    The 12v battery has nothing to do with starting the ICE. Its purpose is to "boot up" the electronic system and power the accessories briefly before the traction battery takes over. The ICE is started by a Motor Generator which is powered by the traction battery.

    The reason the ICE is firing up may be on account that the State of Charge is HIGHER than the design threshold and the car is "burning off" the "excess" charge. There seems to be debate on this subject.
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  5. LenP

    LenP Member

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    Well this happened this morning and I only had an 8 mile charge left in the traction battery, which is far from full. As for the 12 volt system...hm I've been sitting in my new toy a lot, playing with the lights, cd, radio, etc. I'm playing and learning how all the new stuff works.....LOL Hey it's new. :D I just wonder if the HV system is coming on to charge the 12 volt system! It seems when you turn the AC or fan on after your moving his doesn't happen!
  6. andyprius

    andyprius Senior Member

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    I think as long as the car is in ready the 14V is being tapped off the HV, something similer to tapping off a small portion of voltage off a transformer ( except that's AC) The 14DC Controlled and regulated voltage is always present to keep the SOC healthy in the 12V system. Now something obviously triggers the engine to charge the HV when nothing else is available. In your case, by sitting in the car with systems on and the HV low, the computer(s) are calling for a HV Battery charge. Operation is identical, ( it appears) to the previous Prius Generations. Again totally normal. :cheer2:
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  7. LenP

    LenP Member

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    Question since the HV and EV battery is all one, if the EV had 8 miles charge left then wouldn't the HV battery part still be fully charged? By the way if this is my total problem with the PIP I'm a very happy guy. I love this car big time :D
  8. andyprius

    andyprius Senior Member

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    Not having a Pip yet, I assume that the Prius is in normal mode (HV) and still has 8 miles EV reserve left, because the driver elected to use HV. The Soc on the HV would vary as normal, by driver choice, temps, speed, terrain, air pressure etc. :D
  9. Allannde

    Allannde Just a Senior

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    I didn't speak to this question in my earlier post.

    The 12v battery is charged when the car is in Ready through the DC to DC converter (the traction battery is far stronger than 12v which requires the conversion process). The car is NOT on Ready while charging so I suspect that the 12v battery is NOT charging from the wall. I am not absolutely sure of this, but there must be a system to prevent over charging of the 12v battery. That system is deactivated when Ready is off.

    I have installed a Battery Tender for my 12v battery and I discovered that the car was delivered with a 12v battery which was NOT fully charged! It charges at .75 amps and it did reach full charge after 24 hours. If you make mostly short trips like I do, I recommend a Battery Tender.
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  10. LenP

    LenP Member

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    As it turned out my ICE was coming on not due to the 12v battery needing to be charged, but as I found out in another thread, the temp was not set to LOW! It seems Toyota doesn't have a simple heat on/off button on the PIP. They really need it to keep the ICE off easily. The only way to keep it from calling the ICE on, is to set the temp to Low.
  11. devprius

    devprius /dev/geek

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    Or alternately, not run the climate system. No fan, A/C, etc. Settng it to Low may cause the A/C come on, especially if you leave the system in Auto mode.
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