Variable Regen Revisited

[Aaron Cake]

I just happened to be at the 1/4 mile on Friday, which provided me an excellant chance to finally prove/disprove my variable regen observations.

After each 1/4 mile run, there is a long decelleration area, a little more then a 1/4 mile itself. With no traffic to worry about, it makes feathering the brake easy. Also, sine I try to maximize my regen during that period (get the battery ready for the next run) I am always VERY light on the brake. So most of the decel from about 65-70 MPH goes back into the battery.

What I found was that I COULD vary the regen from full to about 1/4 based on pedal pressure. I could easily hold a specific regen level based on pedal pressure for as long as I felt is necessary. There appear to be 4 or 5 regen levels...90%, 80% 60%, 50% and 25%.

Now, I have no idea how the car knows where the pedal is since there aren't any pressure sensors or brake position sensors.

[Yves M.]

I am thinking that it could be an accelerometer into the ECM (or other computer) that figures the way the car decelerates.

I beleive that in a downgrade (computer fooled into thinking that it decelerates more), it is easier the get more regen for the same deceleration.
I saw that going into a montainious area this weekend.

But when you get more recharge, the brake pads are surely touching the disks.

[Holicow]

Did you happen to notice if the percent was related to the speed at the time, or the engine rpm?

[Willie Williford]

The amount of "regen" is determined by several factor, no matter what position the brake pedal is in. They are:

1. state of charge of IMA battery.
2. state of charge of "engine battery".
3. the temperature of the IMA battery.
4. position of throttle pedal. (load on engine)


My opinion.............

[james]

Willie, there has to be a brake pressure sensor in there somewhere, even if it's just a connection to the brake light switch. I frequently drive down a long (~10 miles) downgrade, steep enough that I'll be holding 55-65 mph all the way down with no throttle at all. With no braking, I'll see 4-6 bars of charge, but if I touch the brakes at all, I get the whole display lit. Haven't really tried to hold intermediate values, as what braking I do tends to brief taps...

[Foxpaw]

I do definately have a smooth variable regen on my 2000 Insight. However, it's possible that it is not related to actual brake pedal pressure, but instead perhaps brake pedal pressure is inferred by the ECM based on a change in the vehicle speed sensor.

[Willie Williford]

OK guys, you've got my curosity up, so I installed a (momentary on) switch to activate the "slight pedal" pressure. Now I've got to see what it will do. First impression is that no matter what, the charge will be what the IMA battery wants. With 2 bars down, on decelleration, push the button, no increase. Can't get a "high charge" at low RPM.

Another observation is that when the button is pushed while on a "cruise" mode with the "up shift light" on, the "up shift light" will extinguise.

Tomorrow I will drain the IMA battery down a little (4-6 bars) and see if I can get a coralation on RPM and speed.

If nothing else it will be useful for warning the "tail gaters" to "get off my backside" before I activate the "turbo" and "blow you in the weeds." even at 80 MPH :twisted: ...HEE .....HEE

[Yves M.]

I tried and it is (corrected) related to engine RPM and therefore the MAP sensor. The more vacuum, the more regen. But probably limited by battery temp.

And Willie, where will you put the switch. I've been wanting to put one since a while but I do not see where it could be "ergonomic" (easy to use)


Addition: I think that you need to have the battery real hot from usage. Then the IMA will vary the way it regens. Probably that if the battery was not used much (cold), the IMA will always put full regen

[Holicow]

I did a little check myself yesterday on a hill near my house. Left it in 2nd and tried to vary the amount of regen. Couldn't do it, no matter how light I pressed the pedal. It was off or on, after the brief "rise" it does...you know what I mean.

[Aaron Cake]

Originally Posted by Willie Williford

The amount of "regen" is determined by several factor, no matter what position the brake pedal is in. They are:

I can guarantee 100% that I was changing the amount of regen based on pedal pressure. It takes an extremely light touch to do this. I doubt that the pedal moves enough to even touch the friction brakes. I could (with practice) vary the regen between the points I mentioned. I could go up and down based on pedal pressure.

1. state of charge of IMA battery.

When I started the test, about 4 bars down. When I finished the test, about 1 bar down. I was able to maintain full regen until I ran out of track.

2. state of charge of "engine battery".

No idea, but I can assume nearly full.

3. the temperature of the IMA battery.

Wish I knew, but it was a cool evening, and I made 5 quarter mile runs in about 3.5 hours.

4. position of throttle pedal. (load on engine)

0%.

Did you happen to notice if the percent was related to the speed at the time, or the engine rpm?

No, it was directly related to pedal pressure. At the end of a run, I was going roughly 75MPH in 3rd gear, which gave me all the time I needed to prove this (about 10 seconds until I hit 35MPH, at which point I needed to hit the friction brakes HARD to avoid hitting the trees at the end of the track ).

I still have no idea how the car decides the position of the brake pedal.