Honda Accord Hybrid B mode ? - Page 2 - Fuelly Forums

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Old 05-01-2015, 09:40 PM   #11
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It's been a while since this thread started, but 1motime if you are still monitoring this, it's fine to drive in the B mode. That is a mode to enhance the regenerative braking. Essentially it maximizes the capture of the kinetic energy as you decelerate. It does cause the vehicle to slow down more than normal when you take your foot of the gas, so it takes a little getting used to, but it definitely increases the amount of power that goes toward re-charging the high voltage battery pack. I drive a very hilly road to and from work and use it regularly to collect energy for the batteries as I go down the hills. I also use it as I approach stop signs/Red lights a lot of the time. I find it really helps boost my overall mileage.
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Old 05-13-2015, 01:59 PM   #12
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It is perfectly alright to use "B mode" all the time. I use it when I'm driving in the mountains or twisting winding roads when I accelerate and then slow often. Also, when descending long grades.
I own a 2014 Accord Touring for 15 months now, love it!
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Old 08-22-2015, 01:06 PM   #13
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Oh gods....

Ok, B mode is, in lay terms, engine braking mode equivalent. What happens, ICE flywheel is locked to MG and then ECM, via VVT-i in case of Toyota or, via VTEC in case of Honda, bleeds air, compressed by moved pistons, out through valves, to slow vehicle down. This is why you have that rather peculiar noise coming from the engine in B mode.
Because engine is coupled to MG, hybrid drive, which is a lot based on momentum and inertia for energy regeneration, has ability to charge traction battery at a higher rate, than during regular braking.
No petrol is supplied to the engine in B mode.
As it takes quite a while to charge traction battery to 100%, if this happens in B mode (I had this done quite a few times), then ECM starts wasting produced energy in order to not overcharge battery. I know it's done through the engine, but forgot specific mechanics of it.
In Toyota HSD - Hybrid Synergy Drive - system is designed so that in B mode, vehicle can be accelerated from pedal, just as if you were in D mode. But, as B mode is mechanically engaged by gear shifter, the very moment operator lets go of the pedal, vehicle goes back to braking with engine. At least Toyota user manual says you can drive in D or B mode.
B mode is very useful for gentle slow downs; taking corners; slowing down on slipper surface, as brakes are not engaged; slowing down vehicle on down grade. Some say, it is working very well on snow. I am yet to try that.
Personally,I am using B mode very often, as fancy braking system and to maintain high level of battery charge as much as possible.
I do not see ANY benefit of continuously having B mode engaged. It's pretty much like driving with R foot on gas and L on brake pedals, and pressing them interchangeably. What's the point?
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Old 08-24-2015, 07:02 AM   #14
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B mode in the HSD can't charge the battery faster than D mode from regenerative braking. Simply because part of the braking energy that could be captured by regen is now being thrown away by pumping air through the engine.

In D mode, and barring some other factor to keep the ICE running, when letting off the accelerator completely, the ICE shuts off and the valves close. Without air flowing through the cylinders and out the exhaust, the trapped air acts as a spring in the cylinder. The only way to lose less energy from the turned off ICE is to have a clutch decouple it from the planetary gear of the PSD(power split device; Toyota's name for the planetary gear connecting the ICE and motor/generator 1; it is basically the transmission).

In B mode, the valves are opened, and the engine pumps air like 99% of the cars on the road when coasting in gear. This is basic engine braking. In a non-hybrid, the amount of braking from the engine is low because the transmission is in the highest gear for the car's speed. Downshifting increases the engine braking force by increasing the rpms of the engine; the faster it spins, the more air pumped, the more of the car's forward momentum is is used to move that air. I would not be surprised if Toyota's software also increases the top rpm of the ICE while coasting in B mode.

B mode is simply the downshift option for the hybrid driver that they had in a non-hybrid. It is meant to be used whenever you would downshift in another car; slowing down a steep descent, controlling speed in the snow, etc. It can be used all the time, but like leaving another car in a lower gear all the time, it will ultimately use more fuel as more energy that was used to accelerate to speed is thrown away while decelerating.
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Old 08-24-2015, 04:21 PM   #15
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Dear Oh Gods,
I'm sorry if I misled you when I stated that "I use it all the time". This of course is a figure of speech here. You are correct that it would not make sense to use it all the time.

I'm going to quote Trollbait above:
B mode is simply the downshift option for the hybrid driver that they had in a non-hybrid. It is meant to be used whenever you would downshift in another car; slowing down a steep descent, controlling speed in the snow, etc. It can be used all the time, but like leaving another car in a lower gear all the time, it will ultimately use more fuel as more energy that was used to accelerate to speed is thrown away while decelerating.

In the sense, as described above, "I use it all the time". It's a great feature, and really makes driving in mountainous terrain fun.

I hope this clears this up for you.
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