Regenerative Braking Drive Modes Gimmicky?

If you can coast, then you will accelerate less, and that means you use less energy.

Regen can only regain ~50% or so of the energy you invested, which is much better than friction brakes, but lousy compared to coasting.

NeilBlanchard said:

If you can coast, then you will accelerate less, and that means you use less energy.

Regen can only regain ~50% or so of the energy you invested, which is much better than friction brakes, but lousy compared to coasting.

Click to expand...

Exactly why I found the best way to increase range has nothing to do with the braking modes, but the way you drive. The e-Golf manual makes a point that coasting at a steady speed is the most efficient way to drive, rather than stopping and going all the time. When I accelerate at a reasonable pace and try to maintain constant speed, braking just enough, I get very good results. Also, keeping speed below 60MPH is very important of course. The average mileage estimate for a full battery on my e-golf is between 120 and 130 miles. I average 5-6 mi/Kilowatt hour. My favorite thing to have on the display behind the steering wheel is the average consumption.

I notice no difference in efficiency between using the automatic braking system in the city as opposed to putting my foot on the brake. As you know, putting your foot on the brake activates the regenerative braking system first, not the actual brakes unless you need to stop suddenly.

Something I noticed this morning.

If the car is at 100%, the 'B' mode won't go past the 2nd large charging line (And hence won't jerk and slow down quickly) At times on this same hill I can get it to go all the way to the left on the charging needle.

--
I started the car, put it in B went down the big hill and thought, hmm why isn't the car slowing down a lot compared to yesterday.
I realized that the car was fully charge and B mode doesn't want to fully engage in a fully charged car.
---

I'm also wondering if I'm using more 'Brakes' during this event. (Instead of putting the force on the generator)

Check again tomorrow.

forbin404 said:

Something I noticed this morning.

If the car is at 100%, the 'B' mode won't go past the 2nd large charging line (And hence won't jerk and slow down quickly) At times on this same hill I can get it to go all the way to the left on the charging needle.

--
I started the car, put it in B went down the big hill and thought, hmm why isn't the car slowing down a lot compared to yesterday.
I realized that the car was fully charge and B mode doesn't want to fully engage in a fully charged car.
---

I'm also wondering if I'm using more 'Brakes' during this event. (Instead of putting the force on the generator)

Check again tomorrow.

Click to expand...

What you observed is exactly the expected behavior. Of course if you press the brake pedal more than it can regen at that moment, it will use the friction brake discs.

forbin404 said:

Something I noticed this morning.

If the car is at 100%, the 'B' mode won't go past the 2nd large charging line (And hence won't jerk and slow down quickly) At times on this same hill I can get it to go all the way to the left on the charging needle.

--
I started the car, put it in B went down the big hill and thought, hmm why isn't the car slowing down a lot compared to yesterday.
I realized that the car was fully charge and B mode doesn't want to fully engage in a fully charged car.
---

I'm also wondering if I'm using more 'Brakes' during this event. (Instead of putting the force on the generator)

Check again tomorrow.

Click to expand...

That's because when the battery is already full, there's nowhere for the "regenerated" electricity to go. As we all learned in science class, energy can be converted but not created or destroyed. Train locomotives have a large bank of resistors in the roof to allow the momentun to be converted into electricity which is then dissipated into heat; our cars don't have such a thing.

So yes when your battery is full, you'll be using more friction brakes.

forbin404 said:

Something I noticed this morning.

If the car is at 100%, the 'B' mode won't go past the 2nd large charging line (And hence won't jerk and slow down quickly) At times on this same hill I can get it to go all the way to the left on the charging needle.

--
I started the car, put it in B went down the big hill and thought, hmm why isn't the car slowing down a lot compared to yesterday.
I realized that the car was fully charge and B mode doesn't want to fully engage in a fully charged car.
---

I'm also wondering if I'm using more 'Brakes' during this event. (Instead of putting the force on the generator)

Check again tomorrow.

Click to expand...

So charge your battery so it's 95% full and you can regen slowing down, right from the get go. Solve the problem, don't charge it quite so full.

If you have Car-net in a 2015 model, start charging the car and note the time it will be finished in your smart phone app... click a "screen save" picture, so you know the time you started charging. Take 20 or 25 minutes off of that completed charge time, if you have a 7.2kwh capable charger, and that should put you at very close to a 95% state of charge, and having working regenerative brakes when you start out.

If I am pressed for time to get somewhere, i never recharge the last 20 to 25 minutes shown on my Car Net App if recharging at 7.2kw @240V.

If you don't have an EVSE that plays well with the eGolf's timer charging, limiting charging to less than 100% is easier said than done. In my case I set a reminder on my phone to remind me after a set amount of time to unplug the car, whether physically or via the CarNet app. But occasionally I'll forget and come back to a car with a full battery.

It will exhibit the same characteristics on an extremely hot day even with a discharged battery.

bizzle said:

It will exhibit the same characteristics on an extremely hot day even with a discharged battery.

Click to expand...

How hot are you defining for "extremely hot day", since that is relative to your local weather conditions. At what temperature have you observed this. Keep in mind, the battery gets hot also, adding it's own heat, when being discharged, so how you drive also affects the batteries ability to accept a regeneration recharge.

Current temperature is 113 degrees. Last month our ambient temps were exceeding 120 degrees.

The asphalt probably exceeds 150 degrees. I'm not sure what Arizona is experiencing, but I don't know of any rational person who would argue that those are not "extremely hot" temperatures but you're welcome to try and create an argument about it.

bizzle said:

Current temperature is 113 degrees. Last month our ambient temps were exceeding 120 degrees.

The asphalt probably exceeds 150 degrees. I'm not sure what Arizona is experiencing, but I don't know of any rational person who would argue that those are not "extremely hot" temperatures but you're welcome to try and create an argument about it.

Click to expand...

I am asking at what temperatures do you notice the reduced regeneration from the battery during slowing down with the regenerative modes, regardless of state of discharge.

We need a way to read the battery's actual temperature(s) over the OBD port to know what ambient temps risk the car limiting power

I'll poke around with my VCDS to see if that comes up.

So far I've experienced it whenever the temperature exceeds triple digits (today it was 119).
I didn't experience this before the summer and "winter" temps out here in the valley are still between 85-90 degrees.

The range is currently about half of what I normally expect but I don't attribute it to battery degradation. It seems to be the A/C hammering the range based on the miles/khw that I'm seeing this summer (during the winter I was able to get it to about 4 and now it's often as low as 1.3).

It was 101F yesterday, and I happened to notice some degradation of regenerative braking getting off the freeway from 55mph to a stop. I do this drive 3x a week, it was noticeable yesterday. Even applying the brakes didn't bump the needle fully to the highest regen possible, the battery wasn't taking the recharge like it normally does. Recharge needle was about 60% left on battery.

Provided as a point of reference.

Interestingly, I drove 35 to 40 mph surface streets back, after taking the freeway there, and the regenerative braking seemed back to normal? Same temperatures, maybe 1 or 2 degrees hotter.

What was the available power meter reading? Was it still pointed at Max?

My wife and I almost never go on the freeway so all of my observations about the temperature and braking are in the context of slow city driving (25-35mph).

I believe the power gauge is always at Max on ours unless it's in (or near) the red zone on the charge side. I don't remember because that gauge seems useless because it's always been at Max except once or twice when we nearly hit the red zone and then it was basically in or near its own red zone so I rarely bother to pay attention to it.

It has been shown that multiple fast charges per day will cause the power meter to go down, indicating a reduced ability to put in or take out power from the battery. I was curious if anyone had seen it go down due to ambient battery heating instead of internal battery heating. My thinking was that if regen was limited, it might also be indicated on that small gauge.

It's not indicated, at least on mine. Even when the ambient temperature is high enough to reduce the regenerative braking capability the power gauge still shows max. I'm assuming this is one mechanism that prevents the battery from heating up too much.

I don't have fast charging capability so I can't speak to that causing the power gauge to go down. I've only seen it go down when the battery is nearly empty.

I had my wife take this picture today at lunch. It was charged up to 90% before she left for work this morning.

miimura said:

What was the available power meter reading? Was it still pointed at Max?

Click to expand...

In my case, yes. The only time I have ever seen it not on "Max" was when I had 114 miles on the battery, and 11 miles left on the Guess- O- Meter. Then it was showing about 50%, half way between full power and the red zone. That was in November, temps were around 60F

.