D or B!

[Lord Voltermore]

I think the main issue is the regenerative braking gives some 'engine' braking  effect due to the load on the generator charging the HV battery. In effect you are held back by electro magnets.  Once the HV battery is fully charged the generator must stop charging . Otherwise where would the excess electricity go? When this happens The ICE takes over the  engine braking by conventional means  -using the engine compression. 
There is some downhill regenerative braking in both B mode and D mode.   More in B mode, so it will fill the  battery sooner 

When the ICE has had to take over engine braking duties on a long decent   it can race and get quite noisy .But even descending long and steep mountain passes in D mode  gives sufficient engine braking  with just the  occasional use of the footbrake . Used prudently and moderating your speed from top to bottom you wont need to brake continuously so they wont overheat.   

[Steve_M]

  Once the HV battery is fully charged the generator must stop charging . Otherwise where would the excess electricity go? When this happens The ICE takes over the  engine braking by conventional means  -using the engine compression. 

Its not directly the engine compression that is causing the engine braking, it is still electrical regeneration.

It is the drive motor connected to the wheels that is charging the battery, working as a generator and not the motor connected to the engine. When the battery is fully charged, the motor connected to the engine starts to turn the engine over to waste the extra energy, like it is trying to start the engine, but it does not inject fuel and keeps the throttle closed so there are compression losses, thats why the engine begins to make the loudish noise. At that point the lock-up clutch is not engaged as the gearing would not be suitable at all vehicle speeds.

[aphybrid]

"thats why the engine begins to make the loudish noise."

When descending a very long steep hill (in Morven - look it up folks - A884 hill south of Liddesdale from 256 to 10m elevation) with fully charged battery that "loudish" noise was horrendous.

[Bristol_Crosstar]

When Should you use B mode in a Honda Jazz Hybrid? 

Firstly the B (Brake) mode is designed first and foremost to be used the same way you would downshift to a lower gear in a conventional manual transmission and using the engine overrun braking to cause a drag force and thus slow the car. 

The use of engine-brake/overrun in a vehicle is primarily a form of braking control to enhance drive-ability/stability, and assist the vehicle brakes in a long down hill run.  Indeed in a snow situation the use of engine braking is key to assisting control by keeping the wheels rolling rather than using the brakes and locking up the wheels.

The Jazz Hybrid B mode does not actually change any gears, because there aren’t any, but rather it simulates the act of down shifting a manual car by increasing the overrun drag energy by using the brake-to-drive-battery re-generation system at a higher level than what occurs in the D (Drive) mode.

I fully understand that harvesting as much energy as possible is a good thing, but focusing on that aspect of B mode is missing the point I think.  For me, I just consider it a bonus when using B mode for the reasons I stated earlier. When I need braking over a long period (long downhill) I just flick it back to B and when not required I flick it back to D.  I use it to control the car firstly, and secondly just recognise the benefits of harvesting otherwise wasted energy.

I am not sure using the B mode for normal driving is a good thing because I suspect keeping the drive-battery above normal use charge levels is not a good thing.  I say that because keeping a cellphone or laptop battery 100% charged all the time is allegedly not a good thing either.  I just let the computer/algorithm keep the drive-battery charge where the designers have figured is best.

The Sport Advance I have also has “flappy paddles” braking mode as well as the B shift just to complicate things.  They do what the B mode does but in four increments going up and down between normal D mode braking level to B mode braking level.  I can select a finer level of braking to suit the slope I am going down, or should I ever be on a race track (unlikely) I can keep my hands on the wheel at all times. 

I have read it is done more for the Asian market – it is highly regarded apparently.  But for me it is a novelty with some minor benefit that I use occasionally.

The “flappy paddles” come with a Sport selection as well as Normal and Eco.  This seems to make the throttle very sensitive and keeps the drive-battery at a higher level of charge so when you want to get going the battery has a load of energy and off you go like a scalded cat.  It doesn’t seem to actually reduce the 0-60 time but just makes the car very lively, and nimble off the start line.  It is a lot of fun when a Boy-Corsa pulls up at the lights next to you.

Regarding the paddles the difference between D and B is that in B it remembers the regen level you've selected whereas in D the car cancels the regen when it thinks it's not needed any more, but the same levels of regen are available in both modes, it took me a while to work this out!

[Nicksey]

"thats why the engine begins to make the loudish noise."

When descending a very long steep hill (in Morven - look it up folks - A884 hill south of Liddesdale from 256 to 10m elevation) with fully charged battery that "loudish" noise was horrendous.

I had this once in the Peak district. Not had the car long. Found out that by turning it to D mode It eased it, and keeping foot lightly on the accelerator helped too. I just thought it was me making the transition from freewheeling clutch mode of previous cars, to the automatic set up I had never used before.