Does your regen give you the finger in cold weather?

[unclewoja]

Mine does, and it's really bloody annoying at the moment. During the cooler months, I typically have 2 regen bubbles available to me, increasing to 3 bubbles when I have 4 bars left, and I get full regen usually when I get down to 2 or 1 bar left. I live in a hilly area and it's impossible to pull the car up going down a hill @ 80km/h with only 1/2 your regen working so I end up losing precious energy through the brakes.

But what REALLY annoys me is when I have 2 regen bubbles available, the car gives me the 3rd bubble @ around 10km/h. Then when I set off again, it takes that away and I'm left with 2 bubbles. I could really use that 3rd bubble @ 80km/h at the top of a hill, not @ 10km/h down the bottom. It's like the car is always giving me the finger.

Apparently the guys at Blackburn Nissan say this is completely normal. Has anyone else found the same thing? Quite frankly, I think it's the worst aspect of the car by a long way. It wouldn't annoy me so much if the ADDED mechanical braking to the regen braking. I can't for the life of me understand why Nissan programmed it to drop the regen braking to a bare minimum once the mechanical brakes are activated.

[4wardthinking]

There is a reason for this, although it can be altered according to global whereabouts for some reason.
When the CAN interface gets here, it's one of the first things I'm going to start un-picking.
Actually, it explains why it does this in the manual.
I recently took to having a read too, and there are a number of interesting points in there.
Regen is quite a high current in-rush, and a lot of how it handles it depends on the HV battery parameters at that moment. It's a kind-a self preservation thingy.

[southernvolt]

Mine is the same on cold mornings. After seeing some stuff about Tesla batteries taking in more charge when they're warm I thought maybe I'd get more regen if the battery was warm so I gave it the beans to warm the battery up. Seemed to give me more bubbles.

[EVangelist]

I can't say I've ever noticed this except on the rare occasions I charge to 100% - no regen at all until the battery gets down to about 90%.

Sydney has a moderate climate so perhaps it's not an issue here. I can get 4-5 dots of regen easy when slowing down.

[rusdy]

Aug 23, 2016 13:18:24 GMT 11 unclewoja said:

Mine does, and it's really bloody annoying at the moment. During the cooler months, I typically have 2 regen bubbles available to me, increasing to 3 bubbles when I have 4 bars left, and I get full regen usually when I get down to 2 or 1 bar left. I live in a hilly area and it's impossible to pull the car up going down a hill @ 80km/h with only 1/2 your regen working so I end up losing precious energy through the brakes.

But what REALLY annoys me is when I have 2 regen bubbles available, the car gives me the 3rd bubble @ around 10km/h. Then when I set off again, it takes that away and I'm left with 2 bubbles. I could really use that 3rd bubble @ 80km/h at the top of a hill, not @ 10km/h down the bottom. It's like the car is always giving me the finger.

Apparently the guys at Blackburn Nissan say this is completely normal. Has anyone else found the same thing? Quite frankly, I think it's the worst aspect of the car by a long way. It wouldn't annoy me so much if the ADDED mechanical braking to the regen braking. I can't for the life of me understand why Nissan programmed it to drop the regen braking to a bare minimum once the mechanical brakes are activated.

Yup, it happens to me too. I'm still not sure whether it's due to cold weather or not. I've noticed the reduced regen when the winter started (temperature bar hovers between 4 and 5 bars). However, this didn't happen last year's winter, so it must be something else too.

My guess (pure guess) it's a combination between battery temperature and the batteries' health (maybe Hx, not SOH). My Hx done free-fall after service. Go figure  .

PS: Hx from LeafSPY

[4wardthinking]

Many factors are at play here.
First, the batteries ability to absorb the regen power is dictated by electro-chemical reaction. There is a "sweet spot" temperature within which it can take greater current.
Secondly the HV controller will need to apportion out a predicted 'space' in the pack for regen versus batteries increased potential as the pack begins to warm up in use. It may increase its potential charge by 5% as it warms in first use time, and it could damage the pack by trying to push 20% back in on regen.
The reaction inside the cell itself isn't uniform across the cells interior immediately, (this is where graphemes electrodes come into play compared to other construction methods) so closer to the electrodes may be 3% more than at the greatest difference between the electrodes, that, if you take the previous figures now gives 8%. Now you have a pack with a 'charged' 88%. Regen only has 12% theoretical space in which to pack itself into.
The Nissan engineers will have taken this into account when setting up the regen aspect. One of the, in fact the biggest killers of Lithium Ion cells is over-charging.
So build in heat, theoretical gain under heat saturation in the first Km or so, increase in charge as heat is produced as the pack is placed under load in use, plus a safety margin. It all adds up.
LiIon cells have a very severe thermo-chemical reaction as they near charge capacity, which as shown earlier, increases their potential.
That's why the last 5% on ones iphone seems to take a long time to complete.

I'll try to find a suitable technical site I can point one to for further information, as my hand writing is not very legible sadly, especially when it's pencil & paper photographed.
Always bear in mind a stated capacity and useable capacity differ considerably. This is also useful if you look at other posts about charge time v applied power from the throttled feed if the standard EVSE we have in the car.
Hope this helps. The manual is a brief users guide, and doesn't delve too deeply. I find the EV is more of a thinkers car, and probably an annexe at the back of the users manual could be useful for those with greater wonder.

[4wardthinking]

Of course, pre-heating the pack increases its immediate 'useability', but that is wasted power remember.

[rusdy]

Aug 25, 2016 9:16:27 GMT 11 4wardthinking said:

Many factors are at play here.

My personal opinion (non technical), there is only one factor: Nissan is 'err-ing' on the safe side for the longevity of their batteries (warranty implication).

If it's a technical reason, then the fast charger will be limited as well during fast charge (is it?). 30kW for less than 5 seconds (during braking) should be easy to be taken by these LMO. The same batteries absorb more than 30kW for minutes (which should handle well during long run of down hill too!).

When it's close to full charge (>80% SOC), then yes, the regen limit is expected. However, we're talking about the regen limitation when the battery is less than 50% SOC (5 bars or so).

PS:
Now I know what you guys talking about 'bubbles'. I never realise the bubbles have 'double wall' when it's available, and 'single wall' when it's not! Me slow 

[unclewoja]

I understand the technical aspects of charging and maintaining the batteries. My biggest beef is that the car gives you extra regen when you need it least, then takes it away as soon as you set off again.

However, I have done 3 100% charges off my level 2 charger at work and the range has increased markedly and regen is much better. I'm still not getting full regen which I fully understand in 4 degree weather but I'm not getting as much of this whole giveth and taketh away of regen.

Reported range has gone from ~120km range with no heating to 145km reported range with no heating last night. This is with 1 bar health loss.

The battery has been acting funny for a while. At home on the 10 amp charger, an "80%" charge would usually result in anywhere from 7-10 bars, whereas on the work charger, I'd always end up with 10 or 11 bars for an 80% charge.

Anyway, a few full charges and the battery seems to be 'refreshed', so I'm a bit happier now.

[4wardthinking]

Actually, I'm beginning to find the same result.
There's nothing wrong with charging Lion cells to as near to 100% as it will allow.
It has increased the SOH as it's known.
The only logical reason I can find for not 100% charging is regen inrush space limitation, which would be wasted as the friction braking is pushed more into play.
Might not make as many trees though!.

[jake]

Just remember that regen is inherently inefficient. That kinetic energy is much better used for forward motion and you will get increased regen when you hit the brake. All you can do is brake early and brake lightly.

[EVangelist]

Aug 26, 2016 13:11:03 GMT 11 jake said:

Just remember that regen is inherently inefficient.

Well, yes, but regen is an order of magnitude better than turning that energy into heat, brake pad dust, or crumpled metal.

My lifeteme regen is currently at 37%.  Meaning 37% of all of the power consumed in driving 17,000 km has come from energy that would have otherwise been wasted.

Imagine if ICE drivers found over one-third of the fuel they used came back into their tank for free.  They'd be having orgasms.

[unclewoja]

Aug 25, 2016 14:53:08 GMT 11 4wardthinking said:

Actually, I'm beginning to find the same result.
There's nothing wrong with charging Lion cells to as near to 100% as it will allow.
It has increased the SOH as it's known.
The only logical reason I can find for not 100% charging is regen inrush space limitation, which would be wasted as the friction braking is pushed more into play.
Might not make as many trees though!.

My assumption for the better range with a few full charges is this. As far as I'm aware, the onboard computer monitors pack voltage to determine charge level. I believe Tesla monitors module voltage.

Now, over time, if you're only monitoring voltage at the pack level, each individual module's voltage will get out of sync for one reason or another, so you might have an 80% full pack, but that's made up of some modules that are 100%, some at 60%, some at 70% etc, all averaging out to 80%.

Some full charges should return all modules to a true 100%. Along this line of thinking, this also feeds into theories I have heard about why Nissan batteries suffer so much degredation. You might end up with 1 or 2 modules at 100% when the pack is only 60% charged, but the charger continues to pump power into them and cooks them. (those figures are obviously extreme examples used to explain my point)

This is all of course assume I'm right about how Nissan monitors the pack voltages. I could easily be wrong on that, but that's what I've heard in the past.

[unclewoja]

Aug 26, 2016 13:11:03 GMT 11 jake said:

Just remember that regen is inherently inefficient. That kinetic energy is much better used for forward motion and you will get increased regen when you hit the brake. All you can do is brake early and brake lightly.

How inefficient is it really? There's no reason why the motor would be less efficient, or at least an appreciable amount less efficient, acting as a generator.

So, the motor is ~90% efficient. Charging results in ~10% power loss. That all works out to an efficiency of ~80%. That's not bad.

Along the line of regen inefficiency thinking, if it's so inefficient then ECO mode should result in a lower range (heating off) that normal D mode because you're using more kinetic energy "inefficiently" in ECO mode.

Don't forget, when you are using regen, you're reclaiming only the energy that was put into the car to accelerate it and counter gravity. You can't get back any of the energy used during cruising because that's a total loss situation where all the energy is lost to heat and noise in one way or another.

[jake]

Yep understand all that, but it is better to keep moving if possible rather than reclaiming some energy while stopping so that you can go again. In other words, it is more efficient to not stop.

I understand what you mean more about the regen problem. I didn't realise about the double bubble thing either. I had always assumed I was getting whatever dots displayed to the left. I am getting good regen with 6 bars remaining. 4 double bubbles. Maybe there is something strange about your car.

[jake]

Also I think you will find that most people see not much difference in range between driving in D and ECO.

[jacky]

Here is the hypermiling guide: www.mynissanleaf.com/viewtopic.php?f=27&t=5508

Since 80% < 100%, using regen unnecessarily is inefficient. Check point 8 in the guide.

If you have enough distance to slow down by losing kinetic energy in air resistance, rolling resistance, etc, use no regen for maximum efficiency.

However, in practice, it is rare to get the car slow down safely without brake or regen. This is why ECO mode was recommended in start and stop traffic.

[4wardthinking]

Many very true remarks here.
Again one has to compare apple with apples.
Remember what the whole concept of Regenerative services. It's a way of reclaiming or capturing what would otherwise be wasted energy. Reclaiming 1% is still energy the vehicle can use again, and that's the key, again. Of course throw in losses along the way, it will not be 1%, merely a fraction of it.
Now the LEAF manual shows there is what one can best describe to be a Sweet Spot in battery temperature. The service that deals with Regen is sensing all the HV batteries parameters dynamically under use, and attempts to get the most from any power it is given.
Regen is easier to think of this way.
Now the Hyper miling is another concept where less power is used in accelerating or decelerating, and avoiding un-necessary rapid changes in either of the two. What's often missed in all these topics is cornering!.
The idea is to slowly add or subtract to the kinetic energy consumed to attain distance, not speed. The LEAF could quite easily travel 200km at 20km/h.
M/S/S..!.
Now I have tried the Hyper Miling myself, and the reality is adopting a new driving style, by that I mean not getting close to the vehicle in front, harsh acceleration, high speed where a little less would make no discernible impact in the journey time, erratic moves or anything like the favourite I often hear is "it says 110, so that's what we should be doing, and those slower are just holding the traffic up".... In my opinion!!. Makes you wonder?.
EV limitations are actually a way to possibly! reduce traffic incidents rather than taking money from drivers, and reducing injuries.. But that's another story.
We have always found that trying to anticipate road and traffic conditions ahead put us in the Hyper-miling category...

Also bear in mind that un-like other forms of propulsion ststems used in vehicles, the LEAF dissipates energy in the friction braking system when it can't safely store it in the HV Battery at any point in time, including cold cells. That energy is wasted just like a Holden & Cart would.
To be able to quantify the losses, one has to apply quite complex mathematics, looking like a vey long string of differentiation.
The Hybrid car can disperse this energy through turning the ice without fuelling it when it can't accommodate it, which demonstrates another facet of losses inherent in the old piston engines!. Add to that the friction braking system, and it's clear that a vehicle has to shed an incredible amount of kinetic energy, no matter what propulsion system it uses.
There are common factors to all vehicles like tyres, gap under the car, purposely very inefficient rego plates etc, etc.

[jake]

On checking the regen on my car from a full charge. I get 4 bubbles available from about 10 bars and then from then it oscillates from 4to 5 bubbles until I have 4 bars left and then it stays on the full 5.
There has got to be something strange happening to have less available and I am wondering why Nissan are saying it is completely normal. Normal would mean most cars right?
What bubbles of regen do others have at various levels of charge？

[jacky]

Aug 28, 2016 1:08:20 GMT 11 jake said:

On checking the regen on my car from a full charge. I get 4 bubbles available from about 10 bars and then from then it oscillates from 4to 5 bubbles until I have 4 bars left and then it stays on the full 5.
There has got to be something strange happening to have less available and I am wondering why Nissan are saying it is completely normal. Normal would mean most cars right?
What bubbles of regen do others have at various levels of charge？

I have the same (10 bars of charge get 3-4 bubbles and get 5 bubbles at 4 bars of charge) since this winter. I think it is the low temperature.

I did a 25kW fast charge yesterday and my battery temperature increased from 5 bars to 6 bars. At a 9 bars of battery charge, it can do only 3 regen initially then 4 after a few brakes. At 6 bars of charge, it can do full regen.

The temperature indicators are known to be not too accurate but it was telling me it was warner than it used to in the last few week and it has better regen at higher battery charge.

[4wardthinking]

The temperature indicator is the mean value of temperature probes.