Noticed something interesting about the regen bubbles

[JohnOver]

Today I charged up to 100% at work and when I left I had no regen, as expected. What I noticed was that the bubbles to the left of center (the regen bubbles) only had one circle, not two like the bubbles on the right.

As I continued home and used up some of the charge, the first bubble to the left of "neutral" got a second circle, and now i was able to regen into it. As I consumed more battery, more of the bubbles got second circles and I was able to fill them up when I regenerated. The double circle in the bubbles was showing me what my maximum regen was...

It's related to more than just battery SOC though. When I entered the on-ramp onto 280S at Page Mill (a long uphill on ramp where I have to be pretty much at 80 kW to keep up with traffic) I had three double-circle bubbles. After pushing hard for about 60 seconds, I noticed that I only had two double-circle bubbles. It went back to three after a few minutes more. It was like the hard acceleration caused the batteries to heat, and the system limited the amount of power that the batteries would accept until they cooled down.

Once again I'm impressed with the amount of information that they are displaying on the rather simple dash.

Has anyone else noticed this behavior?

 

[foobert]

I can't say that I've noticed this, but, then, I so rarely charge to 100%. Next time I'll be looking...

 

[TomT]

Yes, regen is limited by both SOC and battery temperature when at a higher SOC above 80 percent...

Today I charged up to 100% at work and when I left I had no regen, as expected. What I noticed was that the bubbles to the left of center (the regen bubbles) only had one circle, not two like the bubbles on the right.

 

[adric22]

This may sound crazy, but I almost never get to use regen during my morning commute. It is 3 miles to work and most of it is very slow driving due to traffic. I never lose any miles of range from the house to work each morning. Most of the time regen still doesn't work even after I've gotten to work.

However, I've never noticed the inner/outer bubbles like you mentioned. I'll look for that tomorrow morning.

 

[TickTock]

Today I charged up to 100% at work and when I left I had no regen, as expected. What I noticed was that the bubbles to the left of center (the regen bubbles) only had one circle, not two like the bubbles on the right.

As I continued home and used up some of the charge, the first bubble to the left of "neutral" got a second circle, and now i was able to regen into it. As I consumed more battery, more of the bubbles got second circles and I was able to fill them up when I regenerated. The double circle in the bubbles was showing me what my maximum regen was...

It's related to more than just battery SOC though. When I entered the on-ramp onto 280S at Page Mill (a long uphill on ramp where I have to be pretty much at 80 kW to keep up with traffic) I had three double-circle bubbles. After pushing hard for about 60 seconds, I noticed that I only had two double-circle bubbles. It went back to three after a few minutes more. It was like the hard acceleration caused the batteries to heat, and the system limited the amount of power that the batteries would accept until they cooled down.

Once again I'm impressed with the amount of information that they are displaying on the rather simple dash.

Has anyone else noticed this behavior?

Yup. This is curious.

http://www.mynissanleaf.com/viewtopic.php?f=44&t=5582&hilit=bubble&start=239

 

[SierraQ]

They describe this behavior in the manual although not too clearly as I recall. The double-bubble means it is "available." This also works for power bubble too I think, if you should enter turtle mode, although I have not been there to confirm it.

 

[HighDesertDriver]

They describe this behavior in the manual although not too clearly as I recall. The double-bubble means it is "available." This also works for power bubble too I think, if you should enter turtle mode, although I have not been there to confirm it.

Yes, if the car enters a power-limiting mode (We've seen it only at the very low battery state, not for extreme battery temperatures) the double-bubbles will reduce to singles showing those levels are not available. We have noticed only one time where a higher power draw resulted in fewer regen double-bubbles, presumably because the battery temp was marginally increased and crossed a threshold. It was in the first few miles of first drive of the morning after a 100% charge. The car had cold-soaked for about 7 hours after charging had stopped.

 

[evnow]

One bubble opens up for every 10 units of SOC. So,
270 - 1 bubble
260 - 2 bubble
250 - 3 bubble
240 - 4 bubble

But, if you at 240, and going down the hill, quickly the # of bubbles open reduce. You get them back after some driving on stretch without regen.

 

[padamson1]

I live in the hills about 800ft altitude above where I work. I always charge to 80% so that I can get regen as drive to work, but the regen algorithm only gives me 1 bubble of regen at 10bars. The battery temp is laways <= 5bars, so I believe temp is not a factor.

Looking at evnow's table I am wondering why I don't get 3-4 bubbles at 10 bars, then 1-2 bubbles at 11bars (and 0 bubbles at 12bars). I assume that the Nissan engineers know something I don't but it would be really nice to actually get regen when I go down that hill

 

[davewill]

I live in the hills about 800ft altitude above where I work. I always charge to 80% so that I can get regen as drive to work, but the regen algorithm only gives me 1 bubble of regen at 10bars. The battery temp is laways <= 5bars, so I believe temp is not a factor.

Looking at evnow's table I am wondering why I don't get 3-4 bubbles at 10 bars, then 1-2 bubbles at 11bars (and 0 bubbles at 12bars). I assume that the Nissan engineers know something I don't but it would be really nice to actually get regen when I go down that hill

5 battery temp bars can be fairly low. I'd say that the cold is exactly why you're getting less regen.

 

[adric22]

I went out for lunch today and looked at the bubbles. Amazing. I never noticed the "inner" bubbles before. Yet, clearly I could see them and in fact they changed before I returned to work. Sort of like the battery capacity bar that has been staring me in the face and never noticed until somebody mentioned it.

 

[DaveinOlyWA]

yep that is what the double bubbles are is to indicate amount of power coming and going. the lowest i ever got was done to 5 power bubbles. since i was driving around my neighborhood at 25 mph, did not know the amount of power lost. just was doing it to see how fast the bubbles disappeared after turtle mode started. they do go fast. i was losing a bubble every .2 to .4 miles and that was at 25 mph!

 

[padamson1]

5 battery temp bars can be fairly low. I'd say that the cold is exactly why you're getting less regen.

Exactly where this is counter intuitive to me. If 5 temp bars is in fact low, why not increase the regen limit to induce heat into the battery and warm it up to a more efficient temp? Clearly I have know idea the parameters of the charging process, but why not allow regen at the top end where most people start out the drive?

Hopefully there is a good reason for this beyond conservative engineering, because if there isn't there needs to be an override (like the B gear in a Prius).

 

[jkirkebo]

I live in the hills about 800ft altitude above where I work. I always charge to 80% so that I can get regen as drive to work, but the regen algorithm only gives me 1 bubble of regen at 10bars. The battery temp is laways <= 5bars, so I believe temp is not a factor.

Looking at evnow's table I am wondering why I don't get 3-4 bubbles at 10 bars, then 1-2 bubbles at 11bars (and 0 bubbles at 12bars). I assume that the Nissan engineers know something I don't but it would be really nice to actually get regen when I go down that hill

5 battery temp bars can be fairly low. I'd say that the cold is exactly why you're getting less regen.

I agree. I usually have only four temperature bars this time of year, and do not get the last regen bubble before nearing 60% SOC. At 80% (10 bars) I only get one bubble.

 

[HighDesertDriver]

5 battery temp bars can be fairly low. I'd say that the cold is exactly why you're getting less regen.

Exactly where this is counter intuitive to me. If 5 temp bars is in fact low, why not increase the regen limit to induce heat into the battery and warm it up to a more efficient temp? Clearly I have know idea the parameters of the charging process, but why not allow regen at the top end where most people start out the drive?

Hopefully there is a good reason for this beyond conservative engineering, because if there isn't there needs to be an override (like the B gear in a Prius).

The issue is limited by chemistry and reaction rates. At the top end of the charge, the battery is back where it was when it was first built, so to speak. Hammering the battery with power beyond this point may create a little heat from internal resistance, but it will generally not be good for the battery. (Occasional controlled overcharging is another subject entirely and is best addressed by a battery engineer.) At low temperatures, the reaction rates of the battery chemistry slow and it will neither accept (regen) nor delivery power as fast as at the design point. Cool the battery enough, and the outside ring of the "fuel gauge/GOM" will start to shorten, indicating lower battery capacity. (Ref pages 2-9 & 2-10 of the 2011 Manual) There are other issues related to differences between individual cells and their locations within the battery which further complicate the matter. Nissan has rolled all these issues -- and one may guess a fair amount of conservatism -- into the battery management system control algorithms. For a new car under the media and public microscopes, the battery may not have the available power or capacity we would all want, but it has to be a technical home run.

 

[DaveEV]

5 battery temp bars can be fairly low. I'd say that the cold is exactly why you're getting less regen.

Exactly where this is counter intuitive to me. If 5 temp bars is in fact low, why not increase the regen limit to induce heat into the battery and warm it up to a more efficient temp? Clearly I have know idea the parameters of the charging process, but why not allow regen at the top end where most people start out the drive?

Hopefully there is a good reason for this beyond conservative engineering, because if there isn't there needs to be an override (like the B gear in a Prius).

It would be neat if this could be done for those with the battery heater - divert 300W or whatever the battery heater can pull under regen for that use. But then I suspect in typical driving cycles this might not heat the pack up much...