Another Consideration for Battery Life??

[GetOffYourGas]

The pack has a lot of thermal mass and changes temperature slowly...

The surprising thing was that after driving for about half an hour, at about 4.5 m/kWh, the battery temperature was at 78F. In other words, it had risen very little despite a somewhat significant temperature delta from ambient as well as being actively used.

Indeed. For me, that is a good thing which means that I would hardly benefit at all from a TMS system. Unfortunately, for those in hotter climates, this is a major problem since the battery gets little to no time to cool off.

I do wish that Nissan provided more meaningful information to the driver than the coarse (and confusing) temperature bars. The temperature bars don't indicate "too hot" until what - 11 bars? That's obviously the wrong threshold given the toasting of batteries at 8 or 9 bars.

 

[DanCar]

How do we know this?

The people who first had battery degradation issues were driving at 85 mph.

Couldn't find a reference after a quick search, but I recall that is what Nissan said. Anyways driving at 85 mph in phoenix metro highways is somewhat typical, and more true on the outskirts of the metro area. People slow down to 75 where the known speed cameras are at.

 

[abasile]

I have to deal with steep hills and the temp does rise with the high discharge rates required, typically 20kW or more at 25 to 35 mph. Going up moderate grades at 60 mph is a sure way to raise the battery temperature IME. I think the fact that I have to use high discharge rates every time I leave home might be a factor in my battery degradation in what is otherwise a mild climate for a LEAF. I think that abasile has seen this also.

Yes, I definitely have seen the battery temperature go up when I climb our mountain. Before too long I hope to acquire an Android device and the battery app so that I can attempt to quantify this temperature rise.

However, it is unclear to me how much of my LEAF's battery degradation is due to high discharge and charge rates (regen is significant here). My LEAF has spent a significant amount of time down the mountain where the ambient temperatures are often 15-20 degrees (F) higher. These days I'm being more conservative and am not parking the LEAF at work down the mountain if the predicted high temperature in the Valley exceeds roughly 90 F.

 

[kovalb]

There have been many comments and predictions about battery life based on ambient temperature (Arizona, Texas, etc), calendar age of battery, charging to 100%/80%, fast charging, depth of discharge, etc, but I don't recall seeing anything that correlates battery life with the average mile/kwh that the driver gets. It seems intuitive that the easier a battery is driven (using the minimum necessary power needed to get up to speed, maintaining a lower average speed, maintaining a steady speed, etc) will reduce the internal battery heating do to internal resistance, but is maintaining a lower battery temperature the only benefit of conservative driving, or are there other effects of conservative driving that will help preserve battery life?

Averaging a higher energy efficiency (miles/kWh) will extend the battery life. The two primary factors for battery life are number of cycles and time at temperature. A car driven at higher efficiency will consume fewer kWh for any given distance, therefore it will require fewer charging cycles of the battery over its lifetime. To provide some context for the importance of the cycling count, I just drove an 11MY with less than 1,500 miles on it. It has mostly sat parked in the full AZ sun most of its life and is black with no window tint. Yet it still has all 12 SOH bars and I had the indicated range up to 116miles at 6 miles/kWh.

 

[LEAFfan]

How do we know this?

The people who first had battery degradation issues were driving at 85 mph.

Couldn't find a reference after a quick search, but I recall that is what Nissan said. Anyways driving at 85 mph in phoenix metro highways is somewhat typical, and more true on the outskirts of the metro area. People slow down to 75 where the known speed cameras are at.

We haven't had speed cameras for quite some time. I guess the legislators love to speed because the idiots banned the cams on our freeways and interstates. Now, just some cities have them and most don't work.

 

[caffeinekid]

You would really have to be pretty heavy on the accelerator to affect it much, ambient temperature notwithstanding. As for miles/kWH, both my wife and I average 4.1 during the 6 month summer that we have here in Houston. One of our Leafs still lost a capacity bar after a year and a half. The other most certainly will since I QC nearly every week day. My anecdotal evidence states that the Leaf is not well suited to ambient temperatures exceeding 85F for most of the year. An ethical manufacturer would not be selling EVs in such regions without a TMS, but that is another glaring elephant-in-the-room discussion going on elsewhere.

I don't think TMS would make any difference as your battery will still sitting at 85F during the day when parked.

I believe a real TMS would be active whether plugged in or not.

 

[GerryAZ]

You would really have to be pretty heavy on the accelerator to affect it much, ambient temperature notwithstanding. As for miles/kWH, both my wife and I average 4.1 during the 6 month summer that we have here in Houston. One of our Leafs still lost a capacity bar after a year and a half. The other most certainly will since I QC nearly every week day. My anecdotal evidence states that the Leaf is not well suited to ambient temperatures exceeding 85F for most of the year. An ethical manufacturer would not be selling EVs in such regions without a TMS, but that is another glaring elephant-in-the-room discussion going on elsewhere.

I don't think TMS would make any difference as your battery will still sitting at 85F during the day when parked.

I believe a real TMS would be active whether plugged in or not.

If TMS systems are active when parked, what happens when a car with TMS is parked at the airport for 2 or 3 weeks? TMS could not run that long so battery would discharge to TMS cutoff level and then warm up to ambient temperature. Thus, you return to a hot, dead battery--I will stick with Leaf.

Gerry

 

[caffeinekid]

If TMS systems are active when parked, what happens when a car with TMS is parked at the airport for 2 or 3 weeks? TMS could not run that long so battery would discharge to TMS cutoff level and then warm up to ambient temperature. Thus, you return to a hot, dead battery--I will stick with Leaf.

Gerry

That would be a condition of a "primitive" battery (in the words of Musk) system design. A properly engineered TMS would maintain T for much longer....just don't park it with a depleted battery.

 

[dgpcolorado]

Yes, I definitely have seen the battery temperature go up when I climb our mountain. Before too long I hope to acquire an Android device and the battery app so that I can attempt to quantify this temperature rise.

However, it is unclear to me how much of my LEAF's battery degradation is due to high discharge and charge rates (regen is significant here). My LEAF has spent a significant amount of time down the mountain where the ambient temperatures are often 15-20 degrees (F) higher. These days I'm being more conservative and am not parking the LEAF at work down the mountain if the predicted high temperature in the Valley exceeds roughly 90 F.

I think regen heating should be significant for you. I've noticed heating from charging (it is useful in below zero temperatures!) and considering that 3.3 kw charging is tiny compared to the 10-30+ kW experienced with regen going downhill, regen figures to be a big battery heater. For flatlanders, brief slowing or stopping won't generate enough heat to be important. But using regen down your 5000 foot descent ought to cause quite a bit of heating (unless you can coast at terminal velocity...). At least you are starting out in the cool, given parking outside at high altitude.

My destination city can also get warm here, it was in the 90s yesterday (and hit 90ºF at my house at 7670'). But I am only there for a few hours, as opposed to baking in the Riverside/San Bernardino area all day like you deal with. I did heat my battery up to 30.8ºC (~87ºF) yesterday while heading back uphill. But such warm temperatures are brief here and monsoon season should cool things off for much of July and August, I hope: we need the rain, though not the lightning...

 

[abasile]

For flatlanders, brief slowing or stopping won't generate enough heat to be important. But using regen down your 5000 foot descent ought to cause quite a bit of heating (unless you can coast at terminal velocity...). At least you are starting out in the cool, given parking outside at high altitude.

Totally agree. On numerous occasions in Spring and Fall, I've seen the battery temperature go from four bars to five bars on that 5000' descent. But as you say, it's less of a concern when I'm starting with a cool battery. It's the heating from the climb up the mountain in the early evening that concerns me, plus the fact that I have to leave the car parked all day at about 75% SOC to allow a decent margin for the drive home since I'm not allowed to charge regularly at work. (But even if I could charge at work, doing so in the heat is far from ideal.)

Today our high temperature is peaking around 90 F (better than 108 F down the hill), and we're not getting as much nighttime cooling due to monsoonal moisture. The LEAF reached six temperature bars this morning after a drive to/from a nearby mountain community. Thankfully, here at home, I can leave the LEAF parked at 30-40% SOC to mitigate some of the effects of the heat. Other family members can use the LEAF tomorrow, and it is definitely not going to be leaving the relative cool of the mountains.

A Tesla X (or maybe S) with a liquid-cooled, 85kWh battery sure would be nice! We could charge to only 50% and still have plenty of range for most day to day stuff. And regen limits would typically not be an issue.

 

[ksnogas2112]

Side note about battery temp and heat dissipation. It took 7 days for my Leaf to drop back to 5 TB after being at 6 for the previous 2 weeks. Garage temp had to drop to 65* and no charging to dissipate the heat. Even at 75*F and no charging it still wasn't dropping to 5 bars.

Yes, battery temp gauge application is on the to do list.

 

[caffeinekid]

Speaking of considerations for battery life, here is another little gem from Leaf propaganda past"

Nissan's chief vice-president of global marketing communications, Simon Sproule:

"If someone uses the fast charging system every day, they would be doing more than 200 miles (daily) and on an annual basis that would be over 70,000 miles. There aren't many people that drive 70,000 miles a year in any car so it's an unlikely scenario that someone would be fast charging every day. The constant heavy recharge cycle is the extreme and we engineer for the extreme but the reality day-to-day will be nowhere near that."

Sometimes as I get my ~50-60 miles on a 100% charge and have to do more than that in a day, I like to think back to this little bit of BS for a good chuckle. One of these days I am going to put together a compilation of the BS Nissan used to promote their "primitive battery."

http://green.autoblog.com/2011/09/30/nissan-addresses-leaf-battery-life-replacement-costs/

 

[Stanton]

If TMS systems are active when parked, what happens when a car with TMS is parked at the airport for 2 or 3 weeks? TMS could not run that long so battery would discharge to TMS cutoff level and then warm up to ambient temperature. Thus, you return to a hot, dead battery--I will stick with Leaf.

Gerry

That would be a condition of a "primitive" battery (in the words of Musk) system design. A properly engineered TMS would maintain T for much longer....just don't park it with a depleted battery.

I hope you see the folly of your last comment: you can't expect folks to drive around with a "half-full" battery all the time anymore than you can drive around with a "half-full" gas tank all the time! My longest commute is the airport run, and I depend on my Leaf having the same charge level when I return from a trip as when I parked it--or I won't make it home.

 

[caffeinekid]

I hope you see the folly of your last comment: you can't expect folks to drive around with a "half-full" battery all the time anymore than you can drive around with a "half-full" gas tank all the time! My longest commute is the airport run, and I depend on my Leaf having the same charge level when I return from a trip as when I parked it--or I won't make it home.

I totally understand your point, but there is no folly because there shouldn't only be the two extremes available- 1. massive draw and 2. passive thermal management. And in your particular situation, there really should be an allotment of parking spaces available with power outlets at airports (preferably covered as well). After all, even 12V batteries can run down after a couple of weeks sitting. My point is that a proper power delivery system that relies on batteries (ex: EV) should employ thermal management by default, or at the very least in regions like the southern USA or Great Lakes area. Tesla gets it. Even Ford and GM get it, but not Nissan. And now they want to play the "wear down the customer game" as their ineptitude comes home to roost. This is not going to end well for them or the EV push in general.

 

[GetOffYourGas]

My point is that a proper power delivery system that relies on batteries (ex: EV) should employ thermal management by default, or at the very least in regions like the southern USA or Great Lakes area.

I'm curious why you include the Great Lake area. I think up here, the TMS is actually less important than elsewhere. AFAIK, TMS helps more with heat than cold. It's humid up here, but doesn't get all that hot. (ok, I feel like I'm baking right now, but it's only 82F. How hot is it in Texas?). In the cold, TMS might help, but really only when plugged in to decrease charge time / increase energy storage. When driving, heating the battery is a losing proposition - you're going to use more energy doing that than you'll gain in terms of capacity / range. Am I missing something?

 

[dgpcolorado]

I'm curious why you include the Great Lake area. I think up here, the TMS is actually less important than elsewhere. AFAIK, TMS helps more with heat than cold. It's humid up here, but doesn't get all that hot. (ok, I feel like I'm baking right now, but it's only 82F. How hot is it in Texas?). In the cold, TMS might help, but really only when plugged in to decrease charge time / increase energy storage. When driving, heating the battery is a losing proposition - you're going to use more energy doing that than you'll gain in terms of capacity / range. Am I missing something?

The idea is that a TMS would help battery capacity in very cold weather. As you likely know, a cold battery has significantly lower capacity. With a TMS you could heat the battery while charging and have increased range. The warmer battery would also allow better regen (a LEAF at three or fewer temp bars has rather poor regen, IME). That won't affect you much in the flatlands but it is a big deal where I live. I agree that heating the battery while driving would likely be a losing proposition and it is unlikely that a TMS would work this way.

I charge in a garage that almost never drops below freezing, so I don't experience much cold battery effect. If you park and charge outdoors in below zero weather it would be quite significant.

Still, the main advantage of a TMS is protecting a battery from very hot temperatures; increasing range in very cold weather seems less important, unless winter range is limiting.

 

[caffeinekid]

My point is that a proper power delivery system that relies on batteries (ex: EV) should employ thermal management by default, or at the very least in regions like the southern USA or Great Lakes area.

I'm curious why you include the Great Lake area. I think up here, the TMS is actually less important than elsewhere. AFAIK, TMS helps more with heat than cold. It's humid up here, but doesn't get all that hot. (ok, I feel like I'm baking right now, but it's only 82F. How hot is it in Texas?). In the cold, TMS might help, but really only when plugged in to decrease charge time / increase energy storage. When driving, heating the battery is a losing proposition - you're going to use more energy doing that than you'll gain in terms of capacity / range. Am I missing something?

The negative aspects of warming the pack may be overrated because- as others have mentioned- the battery assembly itself is fairly well insulated. If you get it warmed up enough when charging, the car could probably set for hours before needing to be warmed up again, at which point the TMS could do its job again with minimal discharge. This would be even better if the vehicle could remain plugged in during the day. Also, there is no rule that states that the TMS couldn't be deactivated manually when not required....with a disclaimer screen of course.

 

[GetOffYourGas]

My point is that a proper power delivery system that relies on batteries (ex: EV) should employ thermal management by default, or at the very least in regions like the southern USA or Great Lakes area.

I'm curious why you include the Great Lake area. I think up here, the TMS is actually less important than elsewhere. AFAIK, TMS helps more with heat than cold. It's humid up here, but doesn't get all that hot. (ok, I feel like I'm baking right now, but it's only 82F. How hot is it in Texas?). In the cold, TMS might help, but really only when plugged in to decrease charge time / increase energy storage. When driving, heating the battery is a losing proposition - you're going to use more energy doing that than you'll gain in terms of capacity / range. Am I missing something?

The negative aspects of warming the pack may be overrated because- as others have mentioned- the battery assembly itself is fairly well insulated. If you get it warmed up enough when charging, the car could probably set for hours before needing to be warmed up again, at which point the TMS could do its job again with minimal discharge. This would be even better if the vehicle could remain plugged in during the day. Also, there is no rule that states that the TMS couldn't be deactivated manually when not required....with a disclaimer screen of course.

Ok, I think I understand your reasoning. My confusion was mostly because this thread has been focused on the longevity of the battery, not its ability to hold a charge in the cold.

I don't know whether you really need a fancy TMS to accomplish this, though. The cold weather package already has a battery heater. The problem is that it's only turned on at -4F and that's to prevent the electrolyte from freezing (and destroying the battery). I know others have thrown around the idea of using it to keep a battery warmer when plugged in (so it can hold more charge). AFAIK, that has never been attempted, but it would be very interesting to see whether it would work.

 

[DaveinOlyWA]

Side note about battery temp and heat dissipation. It took 7 days for my Leaf to drop back to 5 TB after being at 6 for the previous 2 weeks. Garage temp had to drop to 65* and no charging to dissipate the heat. Even at 75*F and no charging it still wasn't dropping to 5 bars.

Yes, battery temp gauge application is on the to do list.

in my TTID experiment (temporary temperature induced degradation) i also saw it take several days for the temp bars to go back to 5. This was days in low 70's, nights in upper 50's and light duty charging (averaging 3-4 hours a night 3X in 5 days)

 

[TimLee]

The cold weather package already has a battery heater. The problem is that it's only turned on at -4F and that's to prevent the electrolyte from freezing (and destroying the battery).

I think the "prevent the electrolyte from freezing (and destroying the battery)" statement may be excessive. I'm not aware of any reports of any concern of a LEAF without cold weather package "destoying" the battery if if gets below -4F.
At temperatures less than ~-10F to -15F the battery would be ineffective in making the vehicle move, which is why Nissan added the cold weather package to later 2011 LEAFs and all future LEAFs.
But I have seen no information indicating the electrolyte would freeze and destroy the battery.
If you have such information, please provide the references and information.