What happened to my Regen?

[TickTock]

For reference, here is a plot showing %Hx along with %Capacity:

You can see that %Hx tracked just below %Capacity until the P3227 update. After the reprogram, the %Hx dropped off very quickly.

Nice. Here's the same data for my car. Saw an immediate change in the Hx after the update on 7/10/2013 just like you. Didn't see the Hx plummet like yours did afterward but my Hx was already considerable lower at that point. I have one datapoint from March 2012 on the far left but had only been regularly logging these values starting June.

 

[RegGuheert]

Thanks, TickTock! It's good to see comparisons with others' data.

I have one datapoint from March 2012 on the far left but had only been regularly logging these values starting June.

This looks quite similar to what I've seen: With the old BMS firmware the Hx value gradually diverges from the capacity percentage value. But after P3227, they diverge significantly.

Below 20F, my regen is practically gone. Maybe about 10kW around LBW. I'm guessing you don't have any experience below 30F, but your Hx value is much lower than mine. Do you get any regen at cold temperatures, even at low SOCs?

 

[DaveEV]

That's as much as the old LEAF Advisory Board got. But I do think this topic is on the new board's agenda. Maybe drees will comment on this...

Unfortunately, nothing new to report (not that I could if there was until we were either given specific clearance or the information made public - the NDA is very strict).

BTW Reg, great chart of Ah/Hx pre/post P3227. Looks like Mike will get the bulk effect of low Hx within a couple weeks and Ah should take a few months to "recover". My chart is very similar, but I don't have any Hx data.

My Ah went from 57.3 -> 61.0 Ah pre/post P3227, was back down to 57 Ah within two weeks and fell down to 56 Ah after another two weeks. So at least in my case it didn't take long for Ah to "recover" and then some. Reg's well documented car was the same and I suspect Mike's will be, too.

 

[TickTock]

Do you get any regen at cold temperatures, even at low SOCs?

Well, it's only gotten to freezing (barely) a couple nights here so I don't really experience cold. I do still get regen at lower speeds but am not prepared to comment how Hx (and therefore P3227) impacted me. I definitely saw the temperature effect before the update as illustrated on page 5 of this thread and there may have been a slight change to regen immediately following but nothing dramatic. I guess the thing to do is try to fit a model with speed, SOC, temperature and Hx.

 

[RegGuheert]

Here are another couple of ways to look at Hx:

The BLUE curve (left axis) is a plot of how many percent lower the Hx value is than the percent capacity. As you can see, Hx has dropped to a value ~14.5% lower than percent capacity in our LEAF.

The RED curve (right axis) is a plot of the Hx value as a percentage of the percent capacity. In other words, the RED curve is a plot of what you need to multiply capacity by in order to get Hx. So, whatever that thing is that Nissan multiplies capacity by to get Hx has dropped by ~18% since our LEAF was new. (And likely they changed what comprises this factor for the P3227 update).

 

[TickTock]

Interesting how yours seems to be leveling off. I am at 33.5 Hx and 54% SOH. So my ratio is sitting at 62% whereas yours seems to be settling in at 82.5%. Some other data for comparison in the Cap vs. Hx thread.

 

[RegGuheert]

Interesting how yours seems to be leveling off. I am at 33.5 Hx and 54% SOH. So my ratio is sitting at 62% whereas yours seems to be settling in at 82.5%. Some other data for comparison in the Cap vs. Hx thread.

Thanks for that link! Plotting Capacity on top of Hx/Capacity shows that they are virtually identical after my P3227 update:

Put another way, Hx is simply (Percent Capacity)^2 in my case! (But that is true ONLY if I calculate Percent Capacity Remaining using an original capacity of 66.25Ah.)

However, in your case, 0.54^2 is 0.29, not 0.33. Is there any chance your percent capacity is calculated from something other than 66.25 Ah?

 

[TickTock]

I was reporting the SOH directly from the canbus message. My capacity is 35.92Ah and using your formula, that becomes 54.21. So a little closer to 33.5 but not much.

 

[gbarry42]

I read with interest that mwalsh saw the regen go to pot even without the update. While you were clear about the regen behavior, you didn't say specifically that the regen bubbles disappeared just like everyone else was seeing, so I'd like that confirmed. The regen behavior I'm seeing is just like what everyone else complained about, though it seemed to take its time in becoming that bad. It's pretty embarrassing (if I were Nissan) at this point. But I got the update last April, so I kind of think the weather and the age of the battery might be the real culprits.

I remember Honda getting sued after they reduced the use of the battery in their hybrids. I would think Nissan would think twice about being so cavalier about neglecting the regen.

There are always theories about limiting regen to protect the battery, but I can't believe putting 30 kW in for 10 seconds (a typical stopping time?) is going to do anything bad, including heat it up. The only thing that would have to be limited is the applied voltage--which would rise along with internal resistance, but the resistance isn't increasing that much. You would have to observe the cell voltages in excess of 4.1 volts before you could use that excuse.

 

[DaveEV]

You would have to observe the cell voltages in excess of 4.1 volts before you could use that excuse.

The only time I see cell-pair voltages getting this high is after a 100% charge and driving gently less than a mile or so and then coming to a gentle stop as the car slows down past ~10mph. All other times it won't get close to 4.1V/cell.

 

[ashnazg]

Adding my info to this thread -- I had no concerns with regen on my 2011 until my last battery checkup on 12/10/2014. I'd lost my second battery capacity bar way back, maybe Feb 2014 or sooner, so no recent capacity loss noted. Since that battery checkup, regen even in ECO almost never goes to three bubbles, even if I have the battery down to 2 bars left. I used to coast down hills without brakes, since the ECO regen would hit 4 or 5 bubbles and actually slow me down. But with that 12/10/2014 checkup, my regen capability is WAY down. My anecdotal average of 65mi/charge is now more like 50mi/charge.

At first, I told myself "it's been tightened to do less on a mostly full battery", but that's been proven false every time I get the battery down to one or two bars. I've told myself "it's the colder temps", but when my Alabama temps have been in the 60s and 70s the last few months, the regen behavior did not change one bit. Just looking at Carwings data, my monthly running average since I got my Leaf hovered around 5.8-6.2W/m. Since the update, it's stayed around 4.2.

I learned early in my Leaf ownership how to effectively get lots of regen gains in my driving. It's been very aggravating to see such opportunities taken from me, each time I experience it every day.

 

[TomT]

I hadn't seen more than 2 bubbles (about 14Kw) of regen in a VERY long time... Partially due to battery degradation and more partially due to P3227...

 

[mwalsh]

I can still get 3 bubbles at lower speeds (below 45mph) on a warmer day, but anything faster than that, or on a colder day, or with a high state of charge...furgettaboutit!

For anything more that 3 bubbles, I have to actually hit the brakes.

 

[DaveEV]

Adding my info to this thread -- I had no concerns with regen on my 2011 until my last battery checkup on 12/10/2014.

Sounds like you finally had all the firmware updates applied to your car given the combination of reduction in GOM readings and reduction in regen. The update that really changes the GOM/SOC-bar readings was pushed out very early in 2011 IIRC - how did you get your LEAF so early?

Even though the GOM reports that you can't go as far as before the update, you should still be able to, though the GOM and battery SOC bars will read lower than they used to which will take some getting used to.

I can still occasionally hit 30 kW of regen, though it takes a 75F+ temp battery pack and a SOC around 30% and speeds around 25 mph to see it these days. The disappearing regen at higher speeds is really what I miss the most right now.

 

[TickTock]

Just got my new battery last week and compared my available regen with before the battery swap.

Prior to the swap, during a recent drive home, my SOC went from 97% to 41% and I never saw more than 2 regen bubbles.
Today, same route with SOC starting from 70% (no need to charge at work anymore) and dropping to 44%, I started with 5 regen bubbles and ended with 9 (almost 10 - only 1kW away!). Pretty big difference in AR between a new and an worn out battery.

 

[DaveEV]

It would be interesting to see what the pack voltage rises to under maximum regen when comparing new/old packs at the same SOC%.

 

[RegGuheert]

Just got my new battery last week...

What?!!!

How will we know about the performance of our batteries after we lose 6, 7, 8, 9, 10, 11 or 12 bars?

Oh, well, I guess we'll manage to muddle through. Congratulations on getting your LEAF whole again!

 

[TickTock]

It would be interesting to see what the pack voltage rises to under maximum regen when comparing new/old packs at the same SOC%.

This is going to be tough. I don't have any appreciable hills where I live. When I saw I had 9 regen bubbles, I tried to see if I could actually get the 54kW available regen that indicates but was never able to get above 45kW before I slowed down too much. Wasn't watching the voltage but that may have been limiting me (it seemed like I was hitting some other limit below the AR limit).

 

[TickTock]

Just got my new battery last week...

What?!!!

How will we know about the performance of our batteries after we lose 6, 7, 8, 9, 10, 11 or 12 bars?

Oh, well, I guess we'll manage to muddle through. Congratulations on getting your LEAF whole again!

Thanks, I did consider trying to hold out until bar 6 but it was getting inconvenient not only for me but my family ("Sorry kids, can't have any heat because Papa's stubborn.") so I finally caved. I got a new traction motor (was making some disturbing grumbling sounds) out of the visit, too, so I really came away with a practically brand new Leaf.

 

[TimLee]

...I got a new traction motor (was making some disturbing grumbling sounds) out of the visit, too, so I really came away with a practically brand new Leaf.

Wow :shock:
That is impressive.
Not been many reports of motor failure.
How involved was the dealer getting Nissan approval for the replacement?
Did they do extensive testing, or authorize based only on noise?
Would be nice to know what was wrong with it, but it likely got shipped back to Nissan for evaluation.

You did a great job on data collection on the first battery.
Maybe you could post final complete graph of its data?
Looking forward to your real world testing of the new 2015 battery chemistry in a hot environement.
Can't wait to see the one year data.