Regen Braking Observations

I just got back from a session of capturing data and graphing it.

- Regen braking can run at full strength down to 7mph but then it just tapers off until it is 0nm at 2mph. The transition is smooth but you are still generating power below 7mph to 2mph.

- As it tapers off at 7mph, friction ramps up at the same rate.

- Regen smoothly ramps up when you first request to stop. If you push the pedal quickly, the ECU actually uses the friction brakes for a moment to begin braking and then transitions to regen by ramping off the friction as regen ramps up.

- The car will never use regen if you start to brake under 7mph, you use pure friction.

- Regen is always used up to the maximum (usually around 768NM) and the ECU will supplement it with any friction needed if you request more stopping force.

- Shifting to neutral while braking does not instantly kill regen, it actually ramps off as friction brakes ramp This takes about 400ms to happen.

- Traction control is interesting ... the computer doesn't mess around and as soon as it want to reign in wheel spin, it applies a high level of pressure to the offending wheel. Think of it this way: in normal driving and braking, I never needed more than 0.76V of pressure at the wheels. To stop wheelspin, the computer applied over 4V worth of pressure



Edit: SGII XGAUGE for friction brake voltage coming soon
Edit2: Both of these examples have a small burst of friction braking at the start, but this is not the case every time. If you smoothly apply pressure to the brake pedal, there is no friction at all until under 7mph. (Of you push harder on the pedal...)

 

I'm running on the stock firmware still -- so I'll be able to see if there are any changes after I get the reflash.

Spiderman: "A big bag of goodies" is all I can say for the data captures.

 

I'm not sure -- I think to calculate power (Watts) you have to also factor in RPM ...

Watts Calculator

When braking you can see the AMPs going into the battery -- and I've seen 80+ amps when hitting 768NM. The batteries run at around 260V, so 80amps * 260V = 20,080 watts...

I think the Nm rating is more to due with braking force being applied, not so much how much power is being generated.

 

Here is something interesting: the computer applies the brakes briefly when you are parked and the ICE is starting or stopping.

 

It has sensors for each wheel, but has a handy metric where (I presume) you see the max pressure of any wheel. I'm not sure exactly how it works... but that's what I was looking at.

I have the PID for Charge/discharge max but don't know how to figure out the math. But one reading I have from the car I know is right shows 23.5kw charge limit and 20.5kw draw limit.

7E2 21 98 is the PID....

 

I will try to figure out the MTH for the SGII so we will know better. It's quite possible it can go up to 25 or above if the battery SoC is low.

 

I will try to get down to the dealer maybe next week for the update, then I'll do some more testing to and logging to see if anything changes. So busy at work these days...