Question: which battery (12V or HV battery) is *directly* feeding these systems? Electric Power Steering Water pump Oil pump (likely mechanical, right?) A/C compressor Radio Dashboard Lights Wipers Brake pump or better said, which of those systems are off the 12V net on which the 12V battery resides? How is the power network setup on the Prius Gen 3?
Note that the AC is driven by the Inverter, not the 12v bus and after your Prius is in "Ready" mode the Inverter puts the 12v battery on slow charge and supplies everything that is on the 12v bus. Your little 12v battery is only used to supply the 12v bus (and most of the items you listed) as you power up and if you start up in "ACC" (press power without stepping on the brake) or "IG ON" (press power a second time without stepping on the brake). JeffD
Jeff brings up the age old question - If you have a charger on a battery and apply a load are you drawing power from the charger or the battery? While you are obviously drawing power from the charger, I like to think of the charger and the battery as one. A little Zen as it were. But to answer your question not directly asked: Electric Power Steering - 12V system Water pump - 12V system Oil pump (likely mechanical, right?) - mechanical A/C compressor - high voltage system Radio - 12V system Dashboard - 12V system Lights - 12V system Wipers - 12V system Brake pump - 12V system with a capacitor bank (just in case) Electrically, you can't really separate the two systems when the car is in "ready". The traction battery (the high voltage one) will supply the inverter/charger to keep the 12V system at about 13.8V. The ICE will be started and run to keep the traction battery at around 60% charge. When the car is off the traction battery is -completely- disconnected from everything but its' control board. So in this state everything must get its' power from the 12V battery. This is why it's a bad idea to sit in the car with it off and use lights, the radio (in accy) etc. You WILL quickly drain the 12V battery, especially if you accidentally have the headlamps on! You CANNOT get to "ready" without -some- 12V power!
Interesting...so David (and others), when I see the amp output on Scangauge (BTA), which I always thought to be purely the hybrid battery, and I see more amps for driving in EV, but I also see more amps if I am stopped and turn on the headlights, or turn on the wipers, does that mean that BTA tracks all electrical power from both the 12v and the traction battery and combines them into one figure?
BTA tracks the HV battery current. This includes the current that drives the Inverter, so if your 12v bus load increases, BTA will register a smaller (about 20x) current increase due to the difference in voltage between the batteries. As an example, My headlights pull about 10 amps (you will see less if you have HID or LED headlights) from the 12v bus. Turning them on should increase BTA by about half an amp. JeffD
Guys, thanks for all the helpful information. I am a bit surprised to see that the A/C compressor is on the HV net, while EPS, Water pump are not. I would expect a similar type of load on all 3 systems, so why not all on the HV battery net? When not in Ready mode, the HV is physically disconnected and cannot feed the 12V net (and charge the 12V battery at the same time). Only when in ready, this happens, feeding - indirectly - the 12V subsystems, right?
Systems that run after a Prius is shut down (e.g. some pumps) need to be on the 12v bus as the safety relays in the HV battery disconnect the HV in the off state. Yes, the HV is disconnected as stated above by two relays in the HV battery. JeffD
Further to what Jeff said, just think about it for a minute. Would you really WANT a 500V water pump? Considering that 12V ones are commonly available and have been a failure/recall point in the Prius, I shudder to think what it would be like with a 500V one! The A/C compressor is run from the 500V system because that pump can demand a few HP. The water pump is low power so doesn't need the high voltage. Hummm, 500V and water. Wonderful mix.
They don't live in the harsh automotive environment, bu if not UL lab tested and approved ... BE AFRAID. JeffD
In order of danger safest to most dangerous: Prius - it's DC or 3 phase AC but ground fault protected and away from people. Spa - in this country at least, is protected by ground fault interrupter and away from people. Hot water heater - it's surrounded by well grounded metal and away from people. Electric kettle - be afraid, very afraid. Has killed people in the past and will in the future. 240V outlets - they are improving but are still dangerous! ANY fault is exciting.
