I've got the B gear in my Prius and my saleswoman told me the Prius taxi drivers use it because it saves your brakes instead of actually braking. So I've begun using it to slow down before braking. I know it charges the battery but I also noticed my Eco icon goes away when I do it and it sounds like the engine (pistons?) are firing. Does this mean I'm using gas/oil when I'm in the B gear?
B gear uses the gas engine running dry to slow the car. IMHO you would be much better off braking to use the generator to recharge the battery. I've had a number of Toyota dealers tell me to use the B gear to get better mileage and I think that is complete BS. I drove my 2005 for 115,000 miles almost entirely up and down mountains in Colorado and I think I used B gear twice and I replaced my front brakes at 100,000 miles. I just don't consider B gear necessary.
The only normal reason to use B mode is in the mountains, coming down long and steep grades. B mode is used to throw away excess energy, so it's not an efficient way to charge the battery. Use normal braking unless a hill is exceptionally steep and long. This will give you the best recovery of energy through regenerative braking, which also saves wear on the friction brakes just as you would with B mode. Tom
Its my understanding that "B" is good for slowing the car down and charging the traction battery, like on long steep grades where constantly applying the brakes may cause them to overheat. Someone please correct me if Im wrong. +1 on Tom's information.
+1 What Tom said. I had this same argument with a person from Toyota Australia (Sales). This is a person who advises the dealer's sales staff, so the misinformation is endemic. I should have put money on it before he asked one of the technical people about it.
Your answer is generally correct with one exception: B mode is not better for charging the traction battery. Normal braking works just as well. There are some small and rather technical differences between the normal regeneration curve and the B mode regeneration curve, but they are not worth considering unless you are technically obsessed or and OCD hyper-miler. Tom
B mode uses slightly more aggressive regenerative braking. If I recall correctly, maximum regeneration comes in sooner, and keeps going a little longer. Some of the posters with instrumentation can give you the exact figures. Tom
Thanks for the information everybody. I was using it to just slow down at stops even (mainly because it reminds me of gearing down in a standard), but I'll just leave it alone now until I find some steep downgrades.
I've done some experimenting with the B setting and if the eco graph is a valid indicator then using the service brake (the pedal) is a much better regenerator for the batteries. When using B, I noticed an initial surge to charge but it subsides quickly to a minimal level though speed is being lost significantly. I've found a very light touch on the brakes provides better regeneration than the B setting and will still eventually stop the vehicle. My concern would be that very light touch on the brakes also activates the brake lights which could cause unnecessary responses from following traffic.
I share the concern about the brake lights being on under light braking. I've always hated following someone who "rides the brakes." It can be a surprise when the person in front switches from easy to hard braking. But, to take advantage of regeneration I found myself riding away going down the mountains of VT and NH on a recent vacation. Maybe I should have been using B?
Try Cruise Control for some descents, if it fits the road conditions. Provided the HV battery is not full, it will apply more regeneration to hold your speed constant. As the battery nears full, CC gradually transitions over to strong compression braking. When you hear a load vacuum cleaner roar under the hood, in either CC or B modes, the engine is in strong compression braking mode.
+1 to Tom for mentioning me Ditto on the thread consensus thus far. There B-Gear is very analogous to a Jake Brake ( I watch Ice-Road Trucker ). As mentioned by Tom, there are differences in how the regen curve looks with the B-Gear as well as when fuel-cut kicks in for B-Gear -vs- D-Gear. All stuff that Consumer Reports could never hit, and really hard pressed to improve your MPG unless your already in the 80+ range. Fun to play around with, and good to surprise tailgaters with no doubt. 11011011
