When my car was about 6 months old, I saw a red light change to red. I was about a block away with no cars in front of me. It was ever so slightly down hill coming up to that light. I slowed with a steady foot. The speed dropped from about 40 down to 20 where I moved the lever to neutral to see what happens. It was like I lost about 50% of my stopping power without the regen braking. I had to press the brakes harder to make the stop at the red light. This in a way was duplicating what Big-Foot talked about when loosing his regen braking while leaving the lever in drive. Although his problem is intermittent.

 

Guys - We may be closer to solving this mystery...

It cut out on me once today on the way home from work and coincidently, it happened as both my front wheels hit a crack in the pavement..

I drove on a bit further and tried to set it up to happen again but was not successful.. Traffic was not cooperating...

I'm generally pretty critical and aware of how my vehicles are performing, what's normal and what's not.. This does not seem normal so I'm not quite ready to write it off as a coincidental anomaly just yet..

For now - it appears that it may well have something to do with an over-sensitive ABS / Traction control system (sensor)..

I'll report back with the rest of my findings.. I plan on pulling the wheels in my shop this weekend and will check out the sensors...

 

While a wonky ABS sensor may well be to blame, also check out the strut action - a strut that allows too much rebound action will cause the ABS to pulse because the tyre won't be in contact with the road. This will be worse with oversize or overweight wheel/tire combos.

 

A very interesting thread.

I've noticed something like this happening a few times recently.

Each time I have been slowing with light braking behind a stopped or barely moving vehicle - and moving at a very low speed myself.

Suddenly I realize that I am no longer slowing - have a feeling as if accelerating (could this be felt effect of regen braking shutting off?) - and find that I then must brake hard to stop b/4 rear-ending.

Most unsettling.

Generally battery is above mid-level charge; not aware of any pavement irregularities to trip ABS.

Will be more aware in future and take closer note of conditions under which this occurs.

 

The brake system on the TCH is designed that if you press enough on the brakes they will switch from regen to full mechanical, like in a panic stop.

I know Big - Foot is not talking about this feature with his problem.

I'm very easy on my brakes and always try to get them to last over 100,000 miles. I did this with my '94 Corolla.

 

Guys,

I'm fairly certain this is by design. Toyota programmed the system to provide for regenerative braking under normal pressure. The system will also "regen" if you back off of the gas and try to "coast". The car will decelerate similar to a conventional car with "engine" braking at that point. All of this will be replaced in a panic stop by the hydraulic brakes plus the regenerative system.

By "slightly" and I do mean "slightly" engaging the brake, this programming will be overridden by a "coast" command. Try this on a slight downhill by backing off of the gas enough to feel the car start to slow. Barely touch the brakes and start increasing the pressure until the car goes into the "freewheel" mode.

By increasing the pressure just slightly more, the regenerative braking will be engaged and you will start slowing again. I have used this to increase my "glide" distance on slight down slopes since another member here pointed this out around a year ago.

 

It would take an idiot to manually downshift a FWD vehicle with a questionable roadbed traction coefficient, Your TCH's regen control is simply protecting you by eliminating front wheel "braking" that you do not intend.

 

Have you noticed that when you start to feel that lack of braking the ICE (gas engine) stops and mpg meter goes to EV mode? That's because when you barking and ICE motor running it does not consume gas, it spins from wheels just like a regular AT transmission. Then it cuts off from a transmission (like pressing clutch on MT) and stops. So the wheels does not have to spin the ICE and it seems like loosing some braking power.

 

Don't disregard the temperature issue. It could well be that when driving into zones of sub-freezing, or even "close to", the regen capability will automatically decline, especially at lower speeds.

 

The crack in the pavement is a great correlation. I drive everyones hybrids and have noticed that on every Toyota and Lexus the Re-Gen seems more sensitive than what I usually drive.

I'm not saying it is bad just more sensitive.

I drive the same roads at the same speeds with all sorts of different hybrids. At one particular 3-way stop there is a crack in the pavement about 150 feet from the stop sign.

I am a light braker and start my deceleration early and hold a steady pedal depression and force.

When I get to that crack I notice a profound change in motor whine, pedal force, and braking behavior.

I also need to push a little harder to stop compared to my "normal" vehicle I drive.

In every hybrid I have seen, driven, and taken apart, vehicle stability and ABS takes priority over Re-Gen. Some are more sensitive than others. Harder tires in cold may trick ABS into thinking there is a possible skid approaching.