My wife & I just purchased a 2007 TCH. I am a big car nut from way back and am intrigued by all the new fancy electric doo-dads & whoosi-whatsits this car has. One of the things I love, and use frequently is the B mode in the transmission.

I read through the owners manual, but it doesn't go into great detail on what exactly is going on when I put my car in B. I know it loads the motors, and generates power while decelerating the vehicle, however im not sure if it could end up causing more harm than good if I use it too often.

Also, what if my battery is near full charge. Would using B mode risk over-charging the battery?

Thanks in Advance,
-Brian

 

B is for engine braking. It's like your 1st gear in a car, very useful when going down a steep hill to save your brakes. In my opinion there is no benefit in using B all the time unless in situations I stated.

It will not overcharge or cause damage if you over-do it, in fact the manual states that frequent use reduces mileage.

 

The B mode will try to stuff as much current into you big battery as possible until it is fully charged at about 80% of capacity.

After that it turns off the fuel to the engine and uses the gas engine as a 'Jake Brake' to restrain the car from descending a hill too fast. In this case energy is wasted as heated air exhausted through the regular engine exhaust.

'Jake Brakes' engine retarders are more commonly found on large diesel trucks.
They are noisy when used and in the case of a large truck it is illegal to use one inside some city limits.

There is some detectable noise on the Toyota when the gas engine retard becomes active.

No one in their right mind would drive around with the B option all the time.

I remember that using the Jake could be very dangerous on wet roads, I almost got killed once in a blizzard when a Jake cut my RPM to 600 at 40 MPH which meant I was sliding down a mountain at 40MPH - not good!

I think the Toyota Hybrid Camry has a computer to detect the issue of wheels loosing traction and can deal with the problem. But I know enough not to try and test it.

 

it will recharge the traction battery up to 100%

B mode disengages when the accelerator pedal is pressed. There is a noise in the engine when in B mode (sounds like in high rpm) There are cases where the B mode is not working (70mph+) and the brake pedal must be pressed to assist. I did this while driving downhill in Colorado.

While going downhill in Arches National Park in Moab UTAH, I used the B mode to slow down at 15mph. At this point my traction battery got charged at 100%

It's really dangerous to shift from D to B when it's slippery or snowy because the speed decreases immediately, not really sure if ABS or Traction control (VDIM) could compensate for this but this is maybe the reason why it didn't work when I was going downhill at 70mph+.

 

Thanks Guys. I understand how Jake Brakes work, and I realize the B mode is just like downshifting a manual trans, or manually selecting 1 - 2 in an automatic. I was just unsure about what exactly the Camry was doing.

I do not drive around in B mode, i just find myself putting it into B mode when I exit the freeway on offramps, approach red lights, slow down for upcomming traffic... etc.

I was also curious what would happen if I were comming home from Tahoe, at 85+ on the downhills, and had to use B to slow the vehicle. The other day I used B to slow down from around 70mph and was alarmed at how the transmission and Gas motor reacted, so i just left it in D and used the brakes to get me below 50mph, where i then went back into B and continued my exit.

 

"B" mode sacrifices regenerative braking, sometimes a significant portion thereof, in favor of engine compression braking. Primary reason is to conserve frictional braking to prevent their overheating, say on a long downhill run.

 

When you use 'B' mode, you are NOT charging your traction battery (or any other battery, for that matter. You are instructing the engine to turn over without any fuel being fed, and the compression of the air in the cylinders is used to slow the car faster than it would slow by either coasting or regenerative braking.

The only way you will charge the traction battery is to use the brake pedal, judiciously, not hard enough to cause it to activate the real wheel brakes.

 

really, where did you get this mis-information?

when I was driving down at 15mph using "B" mode not hitting the brake and hit 100% charge on my traction battery, what do you think charge it? or that blue arrow going into the battery (if you have a nav) when coasting indicates what?

 

FEEL FREE TO USE B MODE AS MUCH AS YOU CAN. I have entire write up on it at toyotanation, feel free to it also.

benefits:
1. faster than regenerative braking traction battery recharge
2. absolutely fantastic for downhill controlled slow downs
3. excellent for engine braking taking sharp corners at high speeds
cons:

not aware of any. Whoever tells you it's hurting anything, does not know what they talking about.

Keep in ind one basic principle"

THIS VEHICLE DOES NOT HAVE TRANSMISSION.

Oops, remembered one con:

IT'S NOT HYDRAULIC BRAKES!! SO, DON'T FORGET TO TOUCH THEM, WHEN YOU REALLY GETTING CLOSE TO OBSTACLE IN FRONT OF YOU!

 

http://www.toyotanation.com/forum/10...34-b-mode.html