So we had a long thread on this and the consensus is Coasting is more energy efficient for around town. Thread here I don't "get" B mode.

 

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.

 

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 🤔🙄.

 

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.

 

Don't get me started

 

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).

 

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.

 

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

 

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.

 

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.

 

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.

 

The GTE has the best, easiest brakes of any car I've driven before. Most cars I've driven have brakes that do very little at the high end, and then become quite sharp over a limited range of motion. Compared to the GTE, which seems to have very progressive brakes. I believe this is a deliberate engineering decision, to allow more of the regen range to map in.

 

It's a very vague question.

I think the answer is 'reasonably effective'.

Please define 'effective' if you are serious about getting a more meaningful answer.

 

When I referred to being ‘effective’, basically I’m asking if the braking regeneration tops up the battery as effectively as in a car like a Tesla. Just wondered if, being a PHEV, VW installed a half arsed regeneration system.

I thought my question was both reasonable and succinct.

 

It will be a little less efficient than a Tesla for two reasons:

* It's limited to 30kW when you lift off, and about 45kW with your foot on the brake. Tesla do 60kW. Polestar is 75kW. Porsche can do up to 250kW when the brake is applied, if the battery is in the right SoC. For the GTE, this means less of the coast down can be recovered before you press the brake pedal.

* It is going into a smaller battery with higher ESR, which will mean greater losses. The motor is also smaller, which will probably result in greater losses.

 

Donald, I was just correcting obvious errors in the post you made, nothing more.

I agree with the broad statement that EVs will have similar regen efficiency, although there are lot of variables to muddy the water, there's no reason in principle it should vary all that much.

 

There were not any errors, you misread it.

The braking power of the recuperation possible in Tesla is going to be 10 times the GTE. While the GTE can do 45kW a Tesla can do 450kW. But 450kW would lock the wheels, so actually it is unlikely to recuperate that much because of the tyres. That is what I said, and I stand by that as correct.

Was there anything else you felt were 'obvious errors' or was [your misunderstanding on] that it?

 

Dude, YOU are the one who claimed that a Tesla would have 10x the braking capacity of a GTE - even though that is clearly not the case in reality. I showed with some simple maths that you could lock the wheels on about 90kW/axle.

I don't know for sure how Toyota are able to charge their battery with such high currents for a small capacity, or even how VW manage it, but they clearly can do so without worrying the battery too much.

I absolutely agree that tyres are the limiting factor in braking! I literally gave you an example of this concept. On this, we do not disagree.

We're done here - I wonder why I even bother engaging with you. Maybe there's something in the back of my mind that thinks you'll change, but you have to always have the last laugh. Ten pages ahead my arse. 😁

 

Dude, YOU are the one who claimed that a Tesla would have 10x the braking capacity of a GTE

.... just like I said in post #28, here we go.

"donald said", "it wasn't what I meant", "Yes you did, because I know what you meant" ....


etc......

- even though that is clearly not the case in reality.

Like I said, I still don't think you read what I wrote...

Whether it will be a factor of 10 in practice I think will more depend on the tyres. Tesla could probably exceed the tyre

I showed with some simple maths that you could lock the wheels on about 90kW/axle.

Proving exactly what I said in the first place Like I said, you didn't seem to have read what I put in the first post.

Why are you trying to 're-prove' something I already wrote, if you actually read it?

I recommend you just go back and re-read my original post. If I have left anything unclear, fine, just ask for clarification that diving straight into your aggressive and rude argument.

I don't know for sure how Toyota are able to charge their battery with such high currents for a small capacity, or even how VW manage it, but they clearly can do so without worrying the battery too much.

I absolutely agree that tyres are the limiting factor in braking! I literally gave you an example of this concept. On this, we do not disagree.

We're done here - I wonder why I even bother engaging with you.

You have this the wrong way around.

 

Gordon Bennett 😳! When I started this thread I thought my question was relatively simple and uncontroversial? The responses have proved to be interesting, entertaining and informative.

I think I can conclude that the regeneration on the GTE is somewhere between 30kW and 45kW. Nothing special, but reasonable.

 

If 'regeneration power' was the question, then yes that has a much more objective answer. I assumed you were trying to ask some question 'combined with' efficiency.

As mentioned, it is possible to calculate the regeneration power from tyre traction, but note that there is a difference between front wheel and rear wheel drive. A rear wheel drive will be able to regen much less power than it can accelerate, and a FWD can regen much more power than it can accelerate, these being large body forces.

The ideal is therefore a 4WD arrangement, which Teslas have, and they will have the capability to regenerate the same amount of power as they can accelerate with. As the Plaid X has 700kW of acceleration power through 4WD, so there is no theoretical restriction on it being able to regenerate 700kW. It's just 'that' backwards. Whether Tesla set a limit on regen power, I don't know but it is not an engineering constraint. I guess the front motors might be lower power than the rear, so the actual max power will not be fully reversible in that way. Won't be far off... I'll make a guess .. 450kW.

 

🤔

 

I'm going to contribute with what I think the OP is asking.

Is the question: all things being equal (braking force applied by user, start and end speed, road surface and angle, etc) how does the GTE fair compared to other cars in generating energy through regen?

Assuming that is the question being asked and me not knowing the actual figures involved, my educated guess based on knowledge of the car and other info I have gleaned from online sources is as follows.
The GTE runs through a multi-speed gearbox. This will offer some losses compared to the majority of full EVs that often have gearbox but only one speed. Also the motor in the GTE is smaller (less powerful) so possible to not be able to generate the same electromotive force. Then you have the actual charging system onboard. This is where I need more info but I'm sure the regen ability is linked to the charging ability. Our cars have a low charge rate as we all know and that will limit how much it can process.

 

Interestingly most knew exactly what I meant when I asked ‘How effective is recuperation’ especially when I went on to say ‘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?’ Sadly one forum member in particular (🦆) found it necessary to have a diatribe about the wording. The words ‘life’, ‘a’ and ‘get’ spring to mind.

 

Not at all. I asked you to clarify the meaning of the word, and you just used the same word again.

Whether others guessed or did not guess what you meant is irrelevant to the fact that you did not ask a coherent question, nor answer coherently when clarification was requested. They could not have 'known' what you meant because what you said was ambiguous.

In fact, it still is, even though you are repeating the same words.

What can 'recharge to the same level' possibly mean, unambiguously?

 

Whatever!

I regard this enquiry closed since I got the answer I was looking for very early on in the thread.

Please feel free to have the last word, if it makes you feel superior. I won’t be reading it.

 

I don't feel superior, just that I totally wasted my time trying to provide the ideal technical response in arduous ambiguous circumstances, as I tried to do in #26, only to then be challenged by people who choose not to actually think about what is being asked nor likely understanding the technology.

Utterly not feeling superior. I feel like a total loser and idiot for even trying to answer a vague ambiguous "newb" question in the first place.

I hope this final post is 'effective' and 'the right level', whatever that means to you.

 

Sometimes a simple question needs a simple answer. I too come from a technical background but I also understand that not everyone does so digging into the detail is not necessary.