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12V Battery Dead From Heater Use

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Maine Prius, Dec 23, 2017.

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  1. KP7

    KP7 Member

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    You can do this if you use the charge schedule and turn on the climate prep setting: (manual p.147)

    Air conditioning-linked setting (“Climate Prep”)
    When the charging mode is set to “Departure”, the vehicle air conditioning system (P. 488, 499) can be set to automatically operate*
    according to the set time. By adjusting the cabin temperature in advance, passengers can enjoy a pleasant interior immediately after entering the vehicle.
    *: Operation starts approximately 10 minutes before the set departure time.

    This ensures that you are using the traction battery for the heat pump (I'm not sure what it does if it is under 15 degrees F).

    That said, with my longer commute where I know the ICE is going to kick in, I prefer to let the ICE warm up in the morning and condition the cabin from its waste heat like normal. Unless I know I can make it somewhere on full EV, I prefer to have all of the gaskets, hoses, fluids, etc. heated up a bit in the winter before I need power from the ICE.
     
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  2. William Tomb

    William Tomb New Member

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    My car did the same thing. Toyota has a service alert on the voltage sensor which allows the bettery to discharge while warming up and plugged in
     
  3. William Tomb

    William Tomb New Member

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    Part replaced 2885037070 also has engine code P058A01
     
  4. 1x1

    1x1 Member

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    In this situation - flat 12v (engine) battery... if you plugged in the car and charged the traction battery, then unplugged it, and then turned on the car (ready mode), would the energy stored in the traction battery not charge the 12v battery (given several minutes or so)?
     
  5. Prodigyplace

    Prodigyplace Senior Member

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    I believe the 12 volt battery is needed to power the charging electronics in the car. :(
     
  6. 1x1

    1x1 Member

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    Well that seems like a missed opportunity - 7.8kW of stored battery power available at one end, and a flat battery at the other..?
     
  7. Prodigyplace

    Prodigyplace Senior Member

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    And 12 volt computers & safety relays controlling it all.
     
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  8. axle2152

    axle2152 Active Member

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    Is there a TSB out for this?

    edit: I would assume the DTC you referenced would be present and possibly the check engine light?

     
  9. Prodigyplace

    Prodigyplace Senior Member

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    @Elektroingenieur tends to keep up on such things.
     
  10. MikeDee

    MikeDee Senior Member

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    Is it true that plugging in the car also charges the 12V battery? I thought it didn't, and the car had to be in ready mode to do so and is charged by the HV battery.
     
  11. Old Bear

    Old Bear Senior Member

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    As I understand the charging circuitry, plugging in the car just delivers line voltage (120 volts Level 1 or 240 volts Level 2) to the circuitry which charges the lithium-ion traction battery. When the car is turned on, the "converter-inverter" takes power from the traction battery and delivers three separate outputs to the trans-axle traction motors, to the 12-volt battery, and to the air conditioning heat pump.

    The converter/inverter does a lot of work, converting the high voltage DC from the traction battery to even higher voltage three-phase AC for the trans-axle motors which propel the car, to lower voltage DC to keep the 12-volt DC battery charged, and also power to the heat-pump compressor.

    You may find John Kelly's Weber Auto video interesting:



    Because there is no source of 12-volt DC to charge the 12-volt battery unless the inverter/converter is operating, it is not being charged by the lithium-ion traction battery when the car is turned off. But this is not any different than in a conventional automobile where the battery is only being charged when the internal combustion engine is running and turning the alternator.

    And, of course, the demands on the 12-volt battery in the Prime is quite different from that in a conventional vehicle. Unlike a conventional internal combustion car, the Prime's 12-volt battery power is to supply the car's electronic control systems and not to provide a huge surge of power to provide "cranking and spark" to start a large gasoline engine. One of the pleasures of the Prime is that it starts right up without all the dramatics of an internal combustion engine even when cold.
     
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  12. axle2152

    axle2152 Active Member

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    @MikeDee When the Prime is plugged in and charging the 12V battery does get a "trickle" charge. I measured a little over 12.5 V (battery was low as this value should be a bit higher if your battery is fully charged like 12.6-12.7). Off the charger the voltage dropped down to 12.2~ V. With the car on, in "Ready", the voltage was 14.4 V

    The reason for this trickle charge isn't so much to charge the battery but the cooling fans in the HV battery run off the 12 V system.

    When the car is finished charging and plugged in the "trickle" charging stops.

    Don't expect it to charge up a dead battery or be able to keep up with heavy drains on the battery while the car is off.
     
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  13. vvillovv

    vvillovv Senior Member

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    I used to "double push" the ON button in the 14 PIP while plugged in and charging. I could also run the A/C while plugged in and charging, at least on very hot days.

    The PIP was ON but not in READY mode.
    The PiP couldn't drive away from the charger while it was being charged.

    ON but not in READY MODE!

    I think that was the issue the OP had?

    The Prime is a bit different, at least the Prime Plus is.
    When I double push the ON button, it looks just like the PIP.

    ON but not in READY MODE.
    The heater, A/C can be turned on, but are not very effective without the ICE running. So heat pump is probably on too.
    I've never tried to turn on the either defroster while plugged in.

    And although there is preconditioning in the Prime, when I've used that nothing shows up on the dash as being turned on. No temp or fan settings are displayed. So I'm not sure if preconditioning uses the heat A/C setting the driver has set or some other settings.

    I also haven't been able, yet to turn on preconditioning while sitting inside the car. But, I can't always get preconditioning to turn on no matter how many times I push the button on the fob.
    Another mystery about how preconditioning works!
     
    #33 vvillovv, Oct 26, 2019
    Last edited: Oct 26, 2019
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  14. bisco

    bisco cookie crumbler

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    now that you've retrieved this ghost of Christmas past, i wonder what happened to the o/p?:confused:
     
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