S modes and 12V battery charging question

1. Correct. You need to stop at some point, once the conditions are correct.

2. The 12V bus is held somewhere around 13.8V during normal operation. 13.2 sounds a tad low, but it's probably an artifact of how you measure the bus voltage.

How are you measuring that voltage?

Tom

 

Current flow is causing a voltage drop between the battery and the MFD. Whatever is drawing the current eases off when in park or neutral.

Tom

 

Just some clarification on the S mode question.

You actually do not have to stop to get into S3. S3 is broken down into two submodes S3a and S3b. S4 (full hybrid mode) is actually the mode you have to stop (or slow down below 7mph) for about 7-10 seconds (also known as an idle check). When your ice is warmed up above 160 deg F (I think its 166) the conditions are right for transition to S4 but you must execute an idle check to get into S4. You are correct that if you never stop for 7-10 seconds after the ICE warms up, you will never transition to S4 but, S3b is almost as efficient as S4.

This thread may help explain it better than me. http://priuschat.com/forums/knowled...12919-five-stages-prius-hybrid-operation.html

 

Take a look at: http://priuschat.com/forums/gen-ii-...charging-12v-step-change-14-0-13-5-volts.html

I think it's normal.

 

As per the link koolingit gave above, it's normal under some conditions.

It should be higher (around 13.8 to 13.9) when you first start the car, but may drop by about 0.5 volts after driving for a while.

It seems to be some kind of attempt at a two stage charger and it may only be enabled if the temperature is over some minimum threshold.

It also seems to be disabled when you are in either "N" or "P" or when you have any cooling function (even just the fan) in operation.

 

The lower charging voltage of the 12V circuit may be due to the much lower drain on the 12V battery by starting the car. The only thing the 12V battery is doing is starting up the computers and powering the main relay connecting the traction battery to the system. That doesn't take much juice.

Perhaps throwing 14.5V at it is a bit excessive due to the very low load on the 12V battery.

I just got a BT OBDII scanner and Torque on my Android phone, so I put a gauge up for my 12V aux battery, since it's 3 years old now and could need replacing in the next couple years. I noticed 13.8V-14.0V on the circuit in normal operation of the vehicle.