What happened to my Regen?

[johnrhansen]

Could it help things to charge the battery to the max a couple times to balance all the cells?

 

[Pipcecil]

to give an idea at how bad it is, during nice weather (80's) which we had maybe a couple of weeks ago - battery temp gauge at 5-6 bars (good temperature), I would NEVER reach full regen capacity no matter how low my car got. Usually only the first 2 bubbles would be available until maybe below 50%, at LBW I finally get all but one bubble available. This is in stark contrast to me gettting all but one regen bubble available after driving 5-10 miles and full availability after about 15 miles.

Also, I charge to 100% every day (twice) so its not a cell balancing issue.

 

[TickTock]

I just realized I posted these results in the wrong thread.

Here are three plots of the exact same route to work in the morning on three separate dates. Blue is speed and red is available regen (bubbles times 6). All starting at full charge (~95%). SW update was on July 10 (just before the middle plot). Top of graph is 90mph for speed and 40 for the available regen. Each 6 steps in the available regen equates to one regen bubble on the dash. There is a clear trend of reduced regen while at speed going into fall and winter.

March 29, 2012, Pack Temp=31C:

August 08, 2013, Pack Temp=29C:

December 11, 2013, Pack Temp=22C:

Here is the drive home on August 8, 2013. Pack Temperature was 37C. I reached 40 (equivalent to almost 7 bubbles)! and 42kW max regen (post sw update but higher temperature and lower SOC than in the morning):

Here's the drive home on December 11, 2013. Pack Temperature was 26C and I never got more than 12kW regen. However, unlike the August return trip, I charged at work so am starting again with a full charge and ending at 49% SOC.

 

[DaveEV]

Here's the drive home on December 11, 2013. Pack Temperature was 26C and I never got more than 12kW regen. However, unlike the August return trip, I charged at work so am starting again with a full charge and ending at 49% SOC.

Wow, it is crazy that you only have 12kW of regen at nearly 80F battery temps.

Now that you're able to log this data, it would be very informative to be able to compare cars with similar battery characteristics with and without the P3227 update.

I still have no idea why Nissan limits regen artificially at higher speeds proportionally. If it were me I'd always allow regen up to what is safe for the battery... The loss of regen at freeway speeds in your last chart at freeway speeds simply sucks - there's simply no capability to recapture any energy until you slow down.

If you were on a steep freeway slope (think Grapevine on I5 in So Cal) you'd be giving up a lot of energy. I imagine that dgpcolorado and abasile feels the effects of this quite frequently.

 

[TickTock]

[trying to recombine threads]

Correct I have not had the Update. I am do to take the car in for the 2nd year service battery check, and likely will get the update. but this is a major change in regen. I was under the impression that it had to be really cold to affect regen. battery pack that day was 57 by the leaf spy program. after some driving and 4 bars showing on battery temp. I have not checked carwings but I will look into this. since my son is driving it more now , I am not sure how accurate that can be since he drives it differently than I ,and does really care about regen/battery driving distance.

I've seen significant reduction of regen (one bubble) with a 50F battery, though it was 25F outside. It makes we wonder if the LEAF is taking ambient temps into consideration as well or exclusively in deciding on the regen available.

Very interesting thought. Here's a theory. Since the graphs clearly show the available regen is a function of power consumption (why it would do this is another question), maybe the reason I see the degradation of available regen at higher temperatures than others is because I am a wimp and turn on the heater if outside temperature drops below 60F. Maybe the extra 2kW drain is enough to trigger the regen constraint. I'll bundle up one of these cold days and see if doing my commute without the comfort of heat improves my available regen.

 

[DaveEV]

Very interesting thought. Here's a theory. Since the graphs clearly show the available regen is a function of power consumption (why it would do this is another question)

Interesting, I interpret your graphs as showing available regen is a function of vehicle speed, not power consumption. It's quite possible that there is some damping effect, but when is limited, but I have never seen any real difference in available regen at the same speed.

It'd be easy to test the difference with logging with two tests:

1. Accelerate at full throttle up to test speed (say 60 mph) and let off accelerator recording regen.
2. Bring vehicle up to speed above test speed (say 20 mph higher than test speed), coast down to test speed feathering throttle to 0-power, when test speed is reached fully let off accelerator.
3. Repeat the above two tests a few times back to back.

I'd suggest doing these tests in ECO mode and also under conditions where regen is limited to 10-15 kW or so.

 

[JeremyW]

Today was a warm day in So Cal. I did two quick charges today and managed to bring my battery up to 37c! :shock: I gained back all my regen circles around 70% soc when in the past I would have one or two missing. I saw up to 80 Amps of regen. The car acted like it did in the summer.

 

[edatoakrun]

[trying to recombine threads]

...
I've seen significant reduction of regen (one bubble) with a 50F battery, though it was 25F outside. It makes we wonder if the LEAF is taking ambient temps into consideration as well or exclusively in deciding on the regen available.

Very interesting thought. Here's a theory. Since the graphs clearly show the available regen is a function of power consumption (why it would do this is another question), maybe the reason I see the degradation of available regen at higher temperatures than others is because I am a wimp and turn on the heater if outside temperature drops below 60F. Maybe the extra 2kW drain is enough to trigger the regen constraint. I'll bundle up one of these cold days and see if doing my commute without the comfort of heat improves my available regen.

As I've posted over the last few winters on various threads, I believe there could be an additional limitation on regen (pre-update) variable with both higher speeds and lower ambient temperatures, possibly for safety reasons.

Think about the possible results from a LEAF driver in ECO instinctively taking their foot off the accelerator after they hit an ice patch while driving down a steep curve at 60 mph...

In previous winters at what were ~ equivalent battery temps, I seemed to see regen (in ECO) reduced most significantly only at higher speeds and lower ambient temperatures.

I did not battery temp info from the App in previous winters, and haven't had the chance to check yet this year due to the bizarre weather so far this Winter (~11 F to ~28 L/H temp range last week, and a ~45 to 65 F L/H yesterday) meaning I've only used "80%" charge on relatively warm days, and needed ~ "90%"+ for the ~60 mile trip with ~2000 ft descent/ascent on the very cold days.

 

[TickTock]

[trying to recombine threads]

...
I've seen significant reduction of regen (one bubble) with a 50F battery, though it was 25F outside. It makes we wonder if the LEAF is taking ambient temps into consideration as well or exclusively in deciding on the regen available.

Very interesting thought. Here's a theory. Since the graphs clearly show the available regen is a function of power consumption (why it would do this is another question), maybe the reason I see the degradation of available regen at higher temperatures than others is because I am a wimp and turn on the heater if outside temperature drops below 60F. Maybe the extra 2kW drain is enough to trigger the regen constraint. I'll bundle up one of these cold days and see if doing my commute without the comfort of heat improves my available regen.

As I've posted over the last few winters on various threads, I believe there could be an additional limitation on regen (pre-update) variable with both higher speeds and lower ambient temperatures, possibly for safety reasons.

Think about the possible results from a LEAF driver in ECO instinctively taking their foot off the accelerator after they hit an ice patch while driving down a steep curve at 60 mph...

In previous winters at what were ~ equivalent battery temps, I seemed to see regen (in ECO) reduced most significantly only at higher speeds and lower ambient temperatures.

I did not battery temp info from the App in previous winters, and haven't had the chance to check yet this year due to the bizarre weather so far this Winter (~11 F to ~28 L/H temp range last week, and a ~45 to 65 F L/H yesterday) meaning I've only used "80%" charge on relatively warm days, and needed ~ "90%"+ for the ~60 mile trip with ~2000 ft descent/ascent on the very cold days.

The phenomenon comes into play well above freezing - absolutely zero chance of ice.

 

[edatoakrun]

...The phenomenon comes into play well above freezing - absolutely zero chance of ice.

Neither ambient nor battery temps near 32F could be used, if there was a safety function in restricting regen at temps where road ice was a possibility.

I saw road ice over the last week, when both current ambient and battery temperatures were in the 50's.

IIRC, I seemed to see indications of greatly reduced regen last year from (dash reported) ambient temps below ~ 45-50 F.

No idea if this would be different after the update, as I've avoided it so far.

 

[TickTock]

OK. Another experiment (I'm not ignoring all the other suggestions - just can only get to them one at a time). Today, I bundled up and drove into work without any heat. I then charged just a little to recreate the same conditions as my August 08 drive home above. Got pretty close. Only different is age and temperature - both are post P3227.

On 08/08/13, I started at 124 gids (61% SOC) and ended at 52 (29% SOC) for my drive home. I had 47.46Ah, 51.7Hx, and 32C pack temperature.


Today, 12/16/13, I started at 130 gids (66% SOC) and ended at 55 (31% SOC). I had 45.38Ah, 48.3Hx, and 17C pack temperature.


So much for the climate control power theory...

 

[DaveEV]

On the way in to work today, a theory popped into my head as to why regen seems worse after the P3227 update.

ECUs typically used internal maps to dictate parameters over a range of values. These maps have have anywhere from a single dimension to 3 dimensions. Certain parameters may depending on the values of various maps.

Anyone with a GID meter for a while has witnessed seasonality of GIDs with them falling rapidly as the weather warms up and rising when the weather cools down. The Ah capacity and Hx reading (which we assume is a representation of internal resistance) were similar pre-3227 update, but now they seem to be rather stable and temperature independent.

Similarly, there will be a series of maps in the car which is used to define the maximum available regenerative braking. In theory, this should be dependent on the pack's internal resistance and state of charge. It also appears to be adjusted by vehicle speed, but lets ignore that for now.

It is my theory that the P3227 update has effectively decreased what the car thinks it's internal resistance is at hot temperatures (85F and above) and increased what the car thinks it's internal resistance is at cooler temperatures (~75F and below). Doing so improved the accuracy of what the car thinks it's capacity is in hot and cold temperatures, but had the side effect of decreasing regenerative braking at cooler temperatures.

This morning I started off down 2 regen bubbles on a 80% charge and pack temps in the mid 60F range. Last two years I was never down more than 1 regen bubble unless I charged over 80%.

 

[TimLee]

Excellent theory drees. Seems very plausible.
Easy to see how the software engineer that changed the internal resistance map to correct the battery capacity incorrect variation with temperature, overlooked the impacts in other maps and adversely impacted regeneration.
A fairly common error when software changes are implemented.
The LEAF advisory board indicated Nissan is looking into the issue.
Hopefully they'll generate a correction of the regenerative braking map before I have P3227 done.

 

[TickTock]

Two more comparative graphs. Here is my drive on 01/02/2013. I don't know the pack temp, Hx, or Ah since we hadn't worked out how to query for this data back then but I was getting 210-220gids on a 100% charge (started with 212 on this plot):

This is one I shared before from 12/11/2013 (196 gids) plotted on the same scale:


Looks like I got one extra bubble back in January during the high speed portion of my commute. Not super conclusive on whether the sw update changed anything without knowing the pack temperature but http://www.wunderground.com/history reports the min and max temperatures for my area to be 32F and 60F on 01/02/2013 and 37F and 71F on 12/11/2013. So if anything, if temperature was all that was involved I should have had even less regen back in January. Seems like drees may be on to something.

 

[FalconFour]

Well, I feel really, really stupid now having just realized that the gauge does this... but I was driving around with the roomie today (a rare occasion) and wanted to fresh him up to speed on the gauges and indicators for driving efficiently. As I was looking around, I realized that the "Eco-meter" (tree meter? whatever that thing's called, with the dashes over the "growing" tree) actually responds to the regen system throttling. So when I push the brake, friction-brake usage is immediately indicated on the display by backing off the gauge. I can use that to balance slowing down over a longer distance, instead of just hoping-and-hoping-and-hoping it'll un-throttle my regen by the time I approach the stop line.

Can't believe I didn't notice that before. But at least now I know what to watch to avoid the worst effects of this little issue. :x

Also, in just that trip, I saw the same kind of behavior I'd been seeing in the graphs and the driving... as I slow down and "request" more regen (when the meter starts to back off), that's when the car starts un-throttling the regen. If I don't request it with the brake pedal, it doesn't supply the regen power. Strange. Seems more and more like an unexpected software glitch that's being compensated by a fail-safe - being forced to lose efficiency due to its own throttling.

 

[abasile]

If you were on a steep freeway slope (think Grapevine on I5 in So Cal) you'd be giving up a lot of energy. I imagine that dgpcolorado and abasile feels the effects of this quite frequently.

Painfully so! Heading down our mountain, I sometimes have to stop and let the friction brakes cool off. That's if I'm trying to have a high enough SOC to make it back up the mountain without re-charging. It's better if I can descend at slow speeds, but traffic doesn't always permit that. If I head down with a lower SOC, then the regen is adequate to avoid excessive friction braking.

With the battery degrading, this is not a good situation for me, as it's much harder to have enough charge to return home. More regular workplace charging would help, but I'm not holding my breath. Otherwise, assuming I'm able to buy a Tesla eventually, the LEAF will be relegated to on-mountain driving only - very few trips down the hill. It's a wonderful vehicle for driving to/from the other mountain towns, thankfully.

 

[FairwoodRed]

I took my leaf to my dealer to have them look at lack of regen. The dealer wrote that it was a result of the LBC programming update. I opened a case with Nissan. While talking to Jason/Nissan about that, he said “I’ll call the dealer, I want to see if they are having a lot of customers with similar issues.”

He could have been buffaloing me, but he sounded sincere. Hasn’t everyone been reporting the lack of regen to Nissan? Shouldn’t they have dozens if not hundreds of case reports by now?

If you haven't reported it to Nissan, do it TODAY!

 

[DaveinOlyWA]

I took my leaf to my dealer to have them look at lack of regen. The dealer wrote that it was a result of the LBC programming update. I opened a case with Nissan. While talking to Jason/Nissan about that, he said “I’ll call the dealer, I want to see if they are having a lot of customers with similar issues.”

He could have been buffaloing me, but he sounded sincere. Hasn’t everyone been reporting the lack of regen to Nissan? Shouldn’t they have dozens if not hundreds of case reports by now?

If you haven't reported it to Nissan, do it TODAY!

have to believe the SW update was flawed. picked up my 2013 today and had all my regen circles even at 70 % SOC and the 2013's were supposedly born with the SW we were updated to

 

[JeremyW]

TickTock, have you noticed this available regen value change when running the heater full out? It *seems* like I get slightly more regen when I'm running the heater/defrost (and pulling 4.5kW)... sorta like a dynamic brake. It would make sense that the regen amps goes into the accessories before going into the battery so we should see higher regen under those conditions (but the same amount into the battery).

Also, congrats Dave on the '13!

 

[brettcgb]

Let me ask this: during all these occurrences of limited regen, is it accompanied by a missing double circle around that green indicator dot? That's what happens on mine, but it only ocuurs with very low temperatures or very high soc. When it's not available the double circle goes away.

The missing double bubbles were what initially tipped me off that something might be happening... I had always seen 5 double bubbles for all SOC<80%, all temperatures. Suddenly, I was never getting more than 3. They didn't gradually go away - one night I had 5, the next morning I couldn't get more than 3. The energy display confirmed my fears.

I've since had the Leaf in for 2nd annual battery inspection, with the comment that regen seems to be having problems. I expected that the P???? update would be installed (and was). The dealer found nothing unusual (as expected).

Regen performance pre- and post-update seems to be very similar. There may be minor differences, or it might be my perception. At any rate, the differences are minor.

I strongly suspect battery health is a major factor. Some health threshold was crossed, and regen is now limited. The limit seems to shift somewhat based on battery temperature, with max regen occurring in a narrow temperature range near mid-scale, as indicated by the instrument cluster.

I haven't done a DCFC since noticing the regen issues. I would think that DCFC and regen limits are very similar, since both would be affected by the battery health. I'm expecting DCFC to take longer (much longer?) than in the past. Is Blink DCFC now reduced from 50kW to 15kW? Has anyone else looked at this?