A day in the life of a Phoenician Leaf Battery

[JPWhite]

/ Is Nissan collecting temp data off of actual owner's cars to work this out? Seems fairly obvious there's a threshold being crossed in Phoenix.

Judging by the features Phil's LEAFscan will support, such as battery temperature, the possibility that Nissan is collecting temp data is there. The warranty excludes temps of over 120 over a 24 hour period. In order to evaluate vehicles for warranty consideration there would have to be at the very least a temperature high-watermark recorded by the vehicle.

The battery check each year is mostly for the benefit of Nissan collecting data about the battery performance/condition. I doubt very much the dealerships understands the data, it simply gets shipped to Japan. The report people get after the battery check says everything is normal, when customers in Pheonix are experiencing suspect behavior from their vehicles. Hopefully Nissan are gathering the data they need to both deal with the customers issues in AZ and also to develop technology ina future MY LEAF to combat the heat.

 

[dznit]

Wonder what difference sliding an "aluminum coated windshield shade" under the Leaf when you park in the morning (weighted down with a couple of bricks) would make on battery temp?

 

[adric22]

Wonder what difference sliding an "aluminum coated windshield shade" under the Leaf when you park in the morning (weighted down with a couple of bricks) would make on battery temp?

I don't know, that might reflect more solar energy up towards the battery pack. Here's a thought, though. I wonder about taking some aluminum tape and coating the belly pan of the car with it? It would work like a radiant barrier.

I'm also curious to hear more details about the cars that have been affected with capacity loss. Did they leave their windows cracked? Or did they allow the cabin temperature to rise to ungodly temperatures for hours on end during the day? Did they park on regular cement, or black asphalt? Were the cars charging during the heat of the day, or just sitting in a parking lot?

 

[DaveinOlyWA]

There has been a lot of speculation on the cause of the rapid battery degradation experienced in Arizona and other hot states beyond what Nissan appeared to expect. Some have suggested that the hot asphalt may be baking the battery beyond the 120F_24hr/140F_absolute_max that the battery is warrantied for.

To shed some light on the topic I purchased a couple of these and stuck one underneath my Leaf for a week. Specifically, on the driver-side, towards the back. I removed three 10mm bolts in the shield there, pulled the shield gently down, shoved the datalogger up against the battery housing, and replaced the screws. This, I believe, gives a good measure of the temperature the battery is being exposed to.

After a week, I've found that the battery was exposed to a maximum of 5 degrees more than the daily max reported by wunderground. This occurred on Thursday when I left work early to run an errand before businesses closed so I was out during the peak heat and saw the battery temp hit 115F versus the reported max of 110F. On my typical days, the battery temperature maxed out at a temp very near the daily max (since I usually leave work after temperature is starting to drop). I also took a log of the EVcan bus on 6/28 to show the amount of charge in the battery at the various temperatures seen throughout the day (plotted below). I did not see anything unexpected or alarming.

the rapid drop in temps on your drive to work suggests that the temp probe is not in a good place. have you tried removing access cover from under back seat and place it there instead?

 

[EdmondLeaf]

My observations concerning undercarriage temp are similar to TickTock, looks like it will be hard to win war with temp. I tend to believe more and more that Leaf battery is not prepared to handle temp higher than other in the same chemistry group. Will love to have 70 for high here but unfortunately we will have 85+ for low several days

 

[TickTock]

A few have asked about the temperature inside the cabin and/or the disconnect hatch. I did have a sensor inside the hatch area - didn't include it in the original plot since I was focusing on the effect of the hot asphalt during the drive, but here it is for inquiring minds. Temperature is shown to rise quite a bit in the hatch area during charging, but not sure if this truly reflects battery temperature. The sensor in the hatch was not pressed against the battery but rather zip-tied to the fuse release. There are also two tubes running through here, I *think* are used for the charger coolant, which may be heating up this cavity.

 

[KJD]

Nice work on the data collection with your car. A couple of observations.

The Temps at night on your battery pack are about 15 or 20 degrees higher than the overnight low for Queen Creek.

During the morning drive the battery temps drop significantly.

During the evening drive home the battery temps go UP significantly.

Could you park the car outside for a couple of nights and then compare the temp charts again?

What about putting a fan next to the car to circulate cooler air under the car at night while parked. The idea being if you could lower the battery temp at night enough it might lower the max temp the pack sees during the day and this might prolong battery life.

 

[September]

the rapid drop in temps on your drive to work suggests that the temp probe is not in a good place. have you tried removing access cover from under back seat and place it there instead?

I think this is likely based on my crappy anecdotal evidence. I have experienced quite high battery temps from QCing (7 bars) with ambient around 40F and never noticed any temp drop even after longer drives. On the morning after drive I was back to 4 bars.

 

[surfingslovak]

the rapid drop in temps on your drive to work suggests that the temp probe is not in a good place. have you tried removing access cover from under back seat and place it there instead?

I can confirm that the emergency disconnect hatch is a good place to get a good idea of the battery pack temp. Unfortunately, charger feed wires are routed through there as well and they will get quite warm (20 F or more above ambient) when the battery is charged, which will invalidate your data. The hatch will stay warm long after charging has finished.

 

[EVDRIVER]

As an interesting note, my pack usually remains about 64-66 degrees under normal driving and about 70 max under hard driving here in the SF area. This weekend I drove to wine country for the weekend, driving very conservative to make my trip on one charge. The temp outside was about 80 and I did climb some slow grades and for the first time I had an extra temp bar. My actual pack temp read from the pack reached a high that weekend of 90 degrees, 71 was my SF record. I never drove the car hard the entire trip so that was the max over ambient however it was only a few degrees over ambient at times until hot parking lots brought it up quickly. I also achieved a new record for high SOC regen after stoping a charge at about 89% actual SOC and was able to get 3-5kw regen after, I suspect this was because the car was just off charge. If I had done this driving at the same SOC after hours of sitting in SF in the 60's it has been be far more restricted. Not what I expected on the regen.

 

[vegastar]

Today I opened the emergency disconnect hatch (it is clean BTW), and found that when the CC fan is working there is a very noticeable flow of air inside the hatch. Is it suposed to be this way?

 

[EVDRIVER]

Today I opened the emergency disconnect hatch (it is clean BTW), and found that when the CC fan is working there is a very noticeable flow of air inside the hatch. Is it suposed to be this way?

Flow which direction?

 

[SanDust]

I also achieved a new record for high SOC regen after stoping a charge at about 89% actual SOC and was able to get 3-5kw regen after, I suspect this was because the car was just off charge. If I had done this driving at the same SOC after hours of sitting in SF in the 60's it has been be far more restricted. Not what I expected on the regen.

Interesting. Do you think this is because the batteries were warmer or because, like pulse charging, the charge has shaken things up and the battery is better able to accept charge? Both?

 

[EVDRIVER]

I also achieved a new record for high SOC regen after stoping a charge at about 89% actual SOC and was able to get 3-5kw regen after, I suspect this was because the car was just off charge. If I had done this driving at the same SOC after hours of sitting in SF in the 60's it has been be far more restricted. Not what I expected on the regen.

Interesting. Do you think this is because the batteries were warmer or because, like pulse charging, the charge has shaken things up and the battery is better able to accept charge? Both?

The warmer temp as it tends to open up regen shortly when cold and perhaps because it was just off the charge cycle. The latter may be more of a guess.

 

[surfingslovak]

The warmer temp as it tends to open up regen shortly when cold and perhaps because it was just off the charge cycle. The latter may be more of a guess.

That would be my guess as well. Jens observed the exact opposite at low temps in Norway.

Today I opened the emergency disconnect hatch (it is clean BTW), and found that when the CC fan is working there is a very noticeable flow of air inside the hatch. Is it suposed to be this way?

Flow which direction?

Noted that too: slight draft from hatch into the cabin. It was without A/C in my case. There appears to be 1/4 of inch space between the pack and the underbody, which would allow air to flow around the battery case.

 

[TickTock]

Do you notice the draft when the battery is cool? Does it stop when CC is off?

 

[vegastar]

Last night I checked again and there was no air flow. When I started to think that I dreamed about the air flow I noticed that I had 5 temperature bars (I had 6 the day before when detected the airflow). So this morning I checked again and with 6 temperature bars (right after charging) the air flow was there. The direction seems to be front to back, but I can't confirm completely as the flow is turbulent and had little time as me wife needed the car (she is always late...)

There is probably a controlled hatch that opens only when the temperature of the battery is above ambient.

 

[QueenBee]

There is probably a controlled hatch that opens only when the temperature of the battery is above ambient.

Or what's more likely is that hot air rises and you are just feeling the convection?

 

[ztanos]

There is probably a controlled hatch that opens only when the temperature of the battery is above ambient.

Or what's more likely is that hot air rises and you are just feeling the convection?

So no convection below 6 temp bars?

 

[vegastar]

It is not convection. Too much flow and it stops when the CC fan is off.