+12V source only in READY mode

Discussion in 'Gen 2 Prius Technical Discussion' started by astrand, Nov 19, 2010.

  1. astrand

    astrand PHEV Guru

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    I need a +12V signal that is only active when the DC-DC converter is active. This is to avoid running a few things when only running on the small AUX battery. To my surprise, it is not easy to find such signal.

    Prius PHEV TechInfo - EAA-PHEV says that IGCT is active when the car is in READY mode, but this isn't true for my car: This signal is also active in ON(IG), but in this mode, the main contactors and the DC-DC converter are not active. This is on a european 2004 model.

    Any ideas? I could of course grab the actual HV battery contactor signal, but it's only available inside the battery. It would be easier if a signal is available in the front of the car.
     
  2. seilerts

    seilerts Battery Curmudgeon

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    You can tap Ready at the HV ECU, H16, #2 wire (green). I don't know offhand if it is +5V or +12V.
     
  3. pEEf

    pEEf Engineer - EV nut

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    The battery contactors are driven by the HV ECU (to the right of the glovebox with grey connectors), which puts out a +12v signal. You could probably piggyback a small relay on this signal without trouble to get this signal. It's a Green Wire (pin #2) on Connector C/H16. (2nd one down from the top). I would not advise exceeding 100ma additional draw on this circuit. This is the same signal that seilerts describes above, but it is NOT the ready signal, it is the coil drive for the +HVB contactor. The actual "Ready" signal is not available as a signal, it's only on the CAN or BEAN bus. The DC-DC startup follows this contactor signal by about 150ms and upon shutdown the DC-DC stops 300ms before the contactor signal goes low, but this is the safest bet without adding a microcontroller to read one of the Busses. The other relatively simple thing you could do is not power up your load until you see a battery voltage over 13V. This would be a sure-fire indication that the DC-DC is online.
     
  4. astrand

    astrand PHEV Guru

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    Thanks! Using the contactor signal CON2 worked fine. The green wire was quite easy to access.

    Btw, I think this is poor design by Toyota. The aux battery is very easily drained, so running PTC heater, seat heaters, all ECUs etc etc when not in READY mode is not a good idea.


    Wrong forum, but anyone knows if this has been changed with Gen III?
     
  5. pEEf

    pEEf Engineer - EV nut

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    I agree. I almost never enable IGN mode. Strangely if you enable ACC mode to listen to the Radio, etc., it times out after about 30 minutes and shuts off. I have never tried this on IGN mode to see if it times out, but hopefully it does.

    My PHEV conversion includes an 8A 13.8v supply to keep the aux battery charged, as I drain at least a few amps from the +12v line while charging for the BMS, LCD display, and Charger cooling fan. If I'm working in the car, I usually am plugged in, so I can use most of the accessories with impunity. (as long as I keep the total below 8A!)
     
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