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Discussion Starter · #1 ·
I appreciate that every time I brake, throttle back (when coasting isn’t deployed) and changing down through the gears using the paddles the battery is charged through recuperation BUT how effective is this recuperation? How much energy is being added to the battery and is it recharging to the same level as a Tesla or any other EV or PHEV? I am very much aware that my GTE will never recharge enough going down a hill to get up the other side - nowhere near. Implying that recuperation is somewhat limited.
 

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I worked out that decelerating from 70mph to 0mph (motorway off ramp for example) I could recuperate around 300Wh. That is roughly one mile of rated range. Indeed, I have seen this in some cases, and I have gained as much as 3 miles down a continuous descent in Scotland. The recuperation isn't however as effective as some cars, the battery charging efficiency at such high 'C' rates is poor, and the car is not as aerodynamic as e.g. e-Golf.

For best regen you also want to be out of GTE mode as GTE mode keeps the engine running even under regen at speeds above 45 mph - this will load the powertrain somewhat.
 

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Discussion Starter · #4 ·
I worked out that decelerating from 70mph to 0mph (motorway off ramp for example) I could recuperate around 300Wh. That is roughly one mile of rated range. Indeed, I have seen this in some cases, and I have gained as much as 3 miles down a continuous descent in Scotland. The recuperation isn't however as effective as some cars, the battery charging efficiency at such high 'C' rates is poor, and the car is not as aerodynamic as e.g. e-Golf.
I live in a hilly area and I find that when going down a long decent the GOM (Guess-O-Meter) might show only a gain of one mile. Then, if travelling on the level the GOM will not actually show a lower range for many miles. I guess the term Guess-O-Meter is rather apt but to be fair I’m only guessing 🤔🙄.
 

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There's definitely something with the GOM where it doesn't like increasing but is quite happy to decrease! For instance if I park up and plug in to my 2.3kW home charging solution (totally not an extension lead out the window) for 30 minutes it will only gain 1 mile but it should have gained (27m*(1/6) = 4.5 miles) in that time. Then if you go driving you can go about 3 miles on that '1 mile' of range. So it hides the gain, but it is still there.

I've also noticed that hybrid mode can borrow a mile of range sometimes! If you switch from e-mode to GTE the range can go down by 1 mile. It doesn't give it back when you switch back to e-mode. I suspect it isn't actually stealing that range, just re-calculating the remaining capacity, or moving some into a buffer for hybrid usage. But it is odd behaviour.
 

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I appreciate that every time I brake, throttle back (when coasting isn’t deployed) and changing down through the gears using the paddles the battery is charged through recuperation BUT how effective is this recuperation? How much energy is being added to the battery and is it recharging to the same level as a Tesla or any other EV or PHEV? I am very much aware that my GTE will never recharge enough going down a hill to get up the other side - nowhere near. Implying that recuperation is somewhat limited.
The maximum energy that can be recovered is the kinetic energy of the moving car, minus the integral of the wind resistance losses, same with rolling friction, multiplied by the efficiencies in the motor, inverter, battery. That's the physics. I would not worry about comparisons with other EVs ( that's a road to madness). As per school level physics, kinetic energy is calculated by 1/2mv(squared).
 

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I don't worry about it too much, I see it as free energy to run the ancillaries while it's in its "charging" phase rather than adding any meaningful mileage to the battery.
 

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I live in a hilly area and I find that when going down a long decent the GOM (Guess-O-Meter) might show only a gain of one mile. Then, if travelling on the level the GOM will not actually show a lower range for many miles. I guess the term Guess-O-Meter is rather apt but to be fair I’m only guessing 🤔🙄.
Yes I found this and also on my Leaf - little GOM range increase but further before the next drop.

In GTE mode the GOM does increase upto about 50% of the normal range. This is one reason why I used it on long journeys, so there was always enough power for the 'battery boost'.
 

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In the 18 months I've had my Passat I've gain a mile only once or twice. I use B mode for safer driving in country lanes so I don't overshoot into a hedge nor field. Definitely more efficient when coasting especially as it suits my driving style.
 

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In the 18 months I've had my Passat I've gain a mile only once or twice. I use B mode for safer driving in country lanes so I don't overshoot into a hedge nor field. Definitely more efficient when coasting especially as it suits my driving style.
And B mode saves wear on the disks and pads too
 

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And B mode saves wear on the disks and pads too
It doesn't make any difference to driving in D mode really, it just automates the operation more.

When you press the brake pedal, it doesn't have a direct connection to the brakes, it will first use regeneration and then blend the brakes in as and when required.
 

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Discussion Starter · #13 ·
It doesn't make any difference to driving in D mode really, it just automates the operation more.

When you press the brake pedal, it doesn't have a direct connection to the brakes, it will first use regeneration and then blend the brakes in as and when required.
This perfectly explains why PHEV brakes come across as being ‘wooden’ and weak on initial application. My dealer lent me a Polo while my Golf was having a software update. The first time I used the brakes I nearly went through the windscreen 😳🙄.
 

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I think it does save brakes a little. You are less likely to lean on the mechanical brakes due to a more proactive regen braking by the system. Probably down to driving style again but I tend to one pedal drive more with b mode than coasting and a little bit of brake rub in D.
 

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When you press the brake pedal, it doesn't have a direct connection to the brakes, it will first use regeneration and then blend the brakes in as and when required.
This is incorrect. There is a direct mechanical connection - this is required in case of total power failure.

The difference between 'D' and 'B' mode is the brakes are making a bit of pressure under 'D' mode even when you have less than full regen, whereas 'B' never activates the brakes.

So, for identical deceleration, 'D' is going to be (slightly) less efficient than 'B'.
 

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Discussion Starter · #16 ·
It gets a little confusing regarding ‘B’, ‘GTE’ etc. My Mk8 doesn’t have either. The set up is different but I guess it has all the same functions. I suspect VW has tried to make the operating system simpler.
 

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This is incorrect. There is a direct mechanical connection - this is required in case of total power failure.

The difference between 'D' and 'B' mode is the brakes are making a bit of pressure under 'D' mode even when you have less than full regen, whereas 'B' never activates the brakes.

So, for identical deceleration, 'D' is going to be (slightly) less efficient than 'B'.
It'll be a form of valve that blends it in, you're right in that there will be some form of backup when there is a power failure but in normal use it will first use the regen if it's available and then blend the normal brakes in afterwards to ensure it still feels like a normal car under braking.
 

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It'll be a form of valve that blends it in, you're right in that there will be some form of backup when there is a power failure but in normal use it will first use the regen if it's available and then blend the normal brakes in afterwards to ensure it still feels like a normal car under braking.
The GTE doesn't have an iBooster like Tesla, it just has a regular electronic brake boosting system. (Similar to an engine-based boost system, but using an electric pump to build up pressure in the hydraulic circuit.)

The pedal feel is changed by altering the amount of boost that this electronic system provides. You can feel the system kick in if you have you foot on the brake when you turn the car on, it will push back somewhat.

The mapping is a combination of electric motor and physical brake actuation, the engineers will have designed the brakes to be softer near the top end by adjusting the design of the brake booster. But, if you are pressing the pedal, the brakes will be applied, even if regen is active. This is essential to the design of the system as the pads are often slightly touching the disc anyway.

There is an electronic brake actuator, for the ACC and emergency braking. I am not certain how this works, however I don't believe it is used for pedal feel. You can feel this system disengage if you take over from the ACC by pressing the brake. The brake will soften gently and return to normal pressure after about a second or thereabouts.
 

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There was considerable discussion about regen versus coasting when this forum was launched nearly 8 years ago and EVs had limited range. I had one of the early i3s (predicted max range 80 miles): on a nice (quiet) day in mid-Wales with an outside temperature of 19C, I managed to get a maximum range of 104 miles by coasting wherever possible. Coasting is not always other road user friendly but it is more efficient than regen braking.

FWiW, BMW’s iX3 has both a standard driving mode D and a one-pedal mode B. When in D mode, the car uses the navigation system and sonor to coast when approaching junctions; traffic lights etc. Using this system in the Lake District a couple of weeks ago, I managed to get an average of 4.4miles/kWh in my iX3. Given that the iX3 weighs almost twice that of an i3, this was pretty impressive.
 

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This perfectly explains why PHEV brakes come across as being ‘wooden’ and weak on initial application. My dealer lent me a Polo while my Golf was having a software update. The first time I used the brakes I nearly went through the windscreen 😳🙄.
My GTE had very sensitive brakes, more so than many cars I've recently owned.

They are not brake by wire - such a system is not allowed due to brake failiure if the electronics packed in.

The brake pedal must directly pressurise the braking system with an electric booster to amplify the pressure.
 
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