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I think I can now make it a fairly hard rule --at least for my car-- that when the SOC gets down to 4 bars, to immediately expect some forced regen. It's been very consistent at exactly this point for some months. I find it happens as soon as that 5th bar disappears, so I watch it like a hawk now and stop any thoughts of EV/assist once it’s down to 5 bars. Sometimes I have kept it from happening by turning on my radio or headlights, and that usually brings the SOC up another bar or two, or at least holds it even.

When it occurs, it’s a mild forced regen, but still it’s a pain--the ifcd falls immediately and acts like it can’t get on its feet again. But at the same time I also feel it in the accelerator pedal. It just doesn’t hold up to my foot any more like when the ifcd is at 100, the pedal just sort of “caves in”. (I’ve always been curious about this – anyone know how a drive-by-wire pedal can possibly react to this condition and provide feedback? In fact I can tell every time it happens without even looking at the gage that the regen is happening, just by pedal feel, so pretty sure I’m not imagining things.)

The forced regen usually lasts only a few miles and it shows 2-3 green bars until it’s back up again. I’d be interested to hear reports from others as to when they see it trigger.

It just doesn’t hold up to my foot any more like when the ifcd is at 100, the pedal just sort of “caves in”. (I’ve always been curious about this – anyone know how a drive-by-wire pedal can possibly react to this condition and provide feedback? In fact I can tell every time it happens without even looking at the gage that the regen is happening, just by pedal feel, so pretty sure I’m not imagining things.)


I experience the same thing with the Prius in the rare event that SoC gets very low (3 bars out of 8) and it decides to charge the battery while accelerating. I'm pretty sure that the sensation is in my head. My theory is that I have a good seat-of-the-pants feel for what a given pedal pressure does under normal circumstances and can recognize when that correlation fails. I automatically push the pedal farther down to get my normal acceleration, which feels strange.

That's the best I can come up with.

Tarabell;

I can totally relate to your issue.
This has been a detail that has been ever-present in my mind from day one. I believe, it remains a little more acute in my case because unlike some folks, I drive mostly in city traffic. So yes, I've been very fanatic about my SoC since last summer, so much so, that I've gone through some extremes to minimize the SoC hit.
If you recall, I even supplement my 12 volt system with a couple of solar panels. I am also already in the process of switching to LED lighting (especially the DRL's) among a few other tricks. So I agree, reducing the downstream device drain helps a great deal.

Its too bad I still need to use the AC just to keep the IPU in the happy/healthy range, because operating the AC even in the most conservative of settings can (in bumper-to-bumper traffic) really dent the SoC very quickly. Fortunately, I believe I am getting better in this balancing act. Still, it is not unusual for me to have at least one forced regen every day in the summer.

Now about feeling the transition to regen through the gas pedal, I certainly do not. It is a throttle by wire (as is in the Prius) so it has little-to no ability to transmit direct vibration feedback. The only real clue I get that a regen (even a hidden one) is taking place is the little bit of extra engine load displayed by the Scangauge and the iFCD reluctance to maintain my target FE. In these cases the engine load reading usually goes up 10% or so when the Battery is being fed.


Cheers;

MSantos

Hey Tarabell-

I understand what you are saying - I experience the same issue when the car goes into 2-3 bar forced regen. It seems to bias toward regen when you are Gliding. Makes the foot pressure requirements a bit different. I assume that it is just defaulting to 2-bar regen even when you start to glide? Make sense?

My car seems to be a little more unpredictable. I've seen it at 4 bars without forced regen (I think), and more often it tends to forced regen at 5 bars. Ah well, like a good cat, perhaps they are just distinguishing their personalities :)

I have the forced regen about every other day this summer - also at 4 bars.

I tend to stay away from 3+ bar assists and FAS gliding if I only have 5 bars SOC. I will sometimes even drop to S or max regen bars coming up on a stoplight/sign just to prop up the SOC.

Even with this, the HCH2 seems to be a little "IMA Happy" - assisting too frequently, lowering SOC ==> forced regen.

I think the "limp" pedal feel may also be that you are pushing it in farther to get the ICE to give you some acceleration (with NO help from the IMA).

I have the forced regen about every other day this summer - also at 4 bars.

I have it about once a week sometimes more, and I'm careful with accelerations and of course overuse of EV. I agree the car is assist-happy and don't see how a normal driver can really avoid it in everyday "I don't look at the gauges" type driving. And those who have lots of hills around--there's nothing they can do and I'm sure they get it much more often.

I think the "limp" pedal feel may also be that you are pushing it in farther to get the ICE to give you some acceleration (with NO help from the IMA).

I thought about this and how it feels to me is that the pedal goes in farther not because I have to push it harder, but because there is suddenly no resistance there. So, I'm not trying to maintain speed, and the regen does slow me down. But my foot pressure hasn't increased.

Again I have to recommend that if anyone hasn't yet driven barefoot in the HCH-II, now (summer) is the time to do it. It's eye-opening.

I have it about once a week sometimes more, and I'm careful with accelerations and of course overuse of EV. I agree the car is assist-happy and don't see how a normal driver can really avoid it in everyday "I don't look at the gauges" type driving. And those who have lots of hills around--there's nothing they can do and I'm sure they get it much more often.

Again I have to recommend that if anyone hasn't yet driven barefoot in the HCH-II, now (summer) is the time to do it. It's eye-opening.


Actually, I think a "normal" driver may use braking and downhill regen more than You or I do, since they may not be looking to avoid the regen as much. This may keep their SOC up = fewer forced regens.

Someone (MSANTOS) correct me if I am off base with this:
- In theory, long term max FE in the current HCH2 would actually be achieved if no regen (braking, forced or otherwise) was sent to the SOC and the SOC just drained out, leaving only the ICE to propel the vehicle. This would be a 1.3L vehicle being driven "perfectly" in that you really drive without brakes (or regen braking) - only wind, tires, inclines slow or stop you...
- In practice, it is very hard to avoid at least some braking at downslopes, stops, etc, so at least some regen is sent back to the SOC. Perhaps for high FE drivers, this regen tends to be less that the IMA assist that the HCH2 is programmed to be used. This imbalance makes the SOC drop to 4 bars.
- The HCH2 ensures that the SOC stays at safe levels by forced regen at 4 bars. You and I may get more of these since we reduce the regen supply with the way we drive.

- What I wonder (dont know) is if you are better off (1) feeding the SOC with regen braking - fewer forced regens, (2) drive without brakes, minimize regen - more frequent forced regen or (3) something else. Im leaning to #2 now.

I have started driving with really thin soled shoes (call them socks) though my Wife considers it an "eye watering, nose closing experience" :p

I get the forced regen quite often. It is also as soon as I drop to 4 bars. The charging is typically 2 bars. What is a bit frustrating is that the forced regen continues for me after I get the charge back up to 5 bars. I believe the charging drops to just 1 bar after 6 bars SOC and 0 bars at 7 bars SOC. For me, I often get around this by doing an FAS after the SOC gets back to 5 bars. This seems to "reset" things after restarting and the behavior is normal again (no forced charging).

What I wonder (dont know) is if you are better off (1) feeding the SOC with regen braking - fewer forced regens, (2) drive without brakes, minimize regen - more frequent forced regen or (3) something else. Im leaning to #2 now.

Something else to throw into the mix: Mike Dabrowski told me that, at least on the Insight, the electric steering can draw a lot of current (he measured it). So if you are FAS-ing a lot, steering can put a drain on the battery.

I experience the same thing with the Prius in the rare event that SoC gets very low (3 bars out of 8) and it decides to charge the battery while accelerating. I'm pretty sure that the sensation is in my head. My theory is that I have a good seat-of-the-pants feel for what a given pedal pressure does under normal circumstances and can recognize when that correlation fails. I automatically push the pedal farther down to get my normal acceleration, which feels strange.

That's the best I can come up with.


3 out of 8 bars usually equal to around 50% state of charge, that's where a majority of your engine power is sucked up by the battery, that's right sucked right up from the wheels robing your acceleration, as you press more on the gas pedal to achive the same acceleration your penalty is just more rpms and less mpg. When its up around 55% (4 out of 5 bars) then when the car feels you need the acceleration more, then it will switch its engine power more to the wheels, slowly putting energy back into the pack as your in crusing mode, the effect diminishes when your SOC reaches 60% the sweet spot for the prius battery. Only by then all the engine's power will be directed towards the wheels, the most efficent mode of operation for the engine, the conversion losses are painful and should be avoid at all possible, if your going to give energy back to the pack better leave it to the hills or any hard regens.

use the engine in its most efficent band of rpm to PROPEL THE CAR AND NOTHING ELSE, otherwise your not driving the prius 100% efficently, turn it off if and force ev mode if efficent band of rpm cannot be sustained!