Detect Friction Brake Use via OBD-II?

[DrDeke]

I recently bought a 2012 Ford Fusion Hybrid and was wondering whether there is any way to tell (for instance, using an OBD-II adapter and a smartphone or computer) when you have reached the maximum rate of regenerative braking and the friction brakes start to kick in.

 

For instance, an OBD-II PID that measures brake system hydraulic pedal, or one that measures the kW or Ampere flow back into the HVB would do the trick.

[murphy]

I recently bought a 2012 Ford Fusion Hybrid and was wondering whether there is any way to tell (for instance, using an OBD-II adapter and a smartphone or computer) when you have reached the maximum rate of regenerative braking and the friction brakes start to kick in.

 

For instance, an OBD-II PID that measures brake system hydraulic pedal, or one that measures the kW or Ampere flow back into the HVB would do the trick.

There is a PID that shows the HVB amperage and whether it is into or out of the battery.

[lolder]

The 10 second maximum HVB charge capability is about 60 amps. The maximum 1 second charge is about 100 amps when the car is new. They both approach 65 amps as the car ages. A Ford engineer is rumored to have said "if a heavy book doesn't fall of the front edge of the passengers seat, you're not using mechanical braking."

[mwr]

Does a braking score of less than 100 mean that you've used the friction brakes? If so, then IMHO friction brakes are being used way more often than whehn a heavy book would fall off the front edge of the passenger seat.

[lolder]

The 2010-12 FFH's do not have a brake score and the Ford engineer comment was . I believe, about Ford Escape Hybrids. The 2013+ FFH's HVB can absorb almost 3 times the energy of the Gen I FFH. Apparently rear pads are used for braking stability long before the maximum regen energy is reached by the front wheels.

[mwr]

Apparently rear pads are used for braking stability long before the maximum regen energy is reached by the front wheels.

That makes sense. The FFH isn't an all-wheel-drive car, so regan braking with front wheels only would certainly have limits. I suppose that means the rear brake pads and rotors will wear out sooner than the front. Has anyone had to replace brake pads or rotors on a 2013-or-later FFH?

[hybridbear]

Does a braking score of less than 100 mean that you've used the friction brakes? If so, then IMHO friction brakes are being used way more often than whehn a heavy book would fall off the front edge of the passenger seat.

Yes. Friction brakes are also used when braking while turning, even though the brake score still says 100%.

[DrDeke]

Thanks everyone!

 

I found the PID for the HVB amperage and found the results to be quite fascinating. I had completely forgotten that the kinetic energy of a moving object is proportional to the *square* of the velocity of the object. Looking at the HVB amps when braking at different speeds points that out really clearly. You can max out the regen current with a very modest brake pedal pressure and rate of slowing the car at 60 mph, whereas at 20-30 mph, you can press the brake pedal much harder and achieve a much greater deceleration before maxing out the regen.

 

Having looked at this for a few days, I feel like I now have a good idea of how best to brake to maximize regen in this car (which, as someone else noted, does not display a brake score).

[Automate]

@DrDeke

Take a look at the anti-lock brake module (ABS). Monitor the PID BRKHYDRESS..when you press on the brakes and you are in regeneration the pressure will stay low (like 10 psi or less). If pressure goes higher you are using friction brakes.

[DrDeke]

Oooh, thanks Automate! I'll take a look at that in the morning.

[DrDeke]

Thanks again Automate; that was exactly the measurement I was looking for. Also very interesting to see the actual brake system pressures that way!

[expresspotato]

I also notice it still says 100% when the battery is stone cold (< 0C) and I can feel its using friction brakes... Guess they did it for a more consistent experience.

[hybridbear]

I also notice it still says 100% when the battery is stone cold (< 0C) and I can feel its using friction brakes... Guess they did it for a more consistent experience.

Correct. 100% just means that you got the maximum the car would allow.

[mwr]

100% just means that you got the maximum the car would allow.

I would prefer that the % means the actual percent energy recovery. Or better yet, two % numbers, one actual, one the % the car allowed.