Volt vs. Leaf - What finally pushed you to the Leaf?

[GetOffYourGas]

Forums are very important to provide information regarding products, especially complex products, and they've certainly influenced my (our) decision. I'm sure moderating is an important and difficult job, but one that needs to be handled with... moderation.

I too have been influenced by comments on a forum. In my case, I was considering the C-Max Energi, but after reading the real-world mileage people were getting at fordcmaxenergiforum.com, I decided it wasn't worth the hassle of importing one.

Congratulations on the Leaf. I hope you have many great years with it!

 

[mbender]

I can't believe that the Volt is actually breaking down that often, so possibly Volt owners don't want to buy gas either, leave the tank empty, and then run out of range. (?) If that's the case, ...

[emphasis added]

I can see how easily an annecdote can be twisted and bended into whatever people like to think.

I don't have any annedocte to share here, nor my own twisted interpretation of such an annecdote. But I do have a fact to share: The Volt has topped the Consumer Reports annual owners' satisfaction survey for 2 years in a row so far.

Whoa! Although I am arguably "anti-petroleum", I'm not particularly "anti-Volt", and would hardly call my speculation "twisted". I was just wondering aloud as to what might explain the disparity in the number of towings. Do you, does anyone have a better hypothesis? (Speculation and hypothesis are quite distinct from "interpretation", of course.)

 

[scottf200]

Whoa! Although I am arguably "anti-petroleum", I'm not particularly "anti-Volt", and would hardly call my speculation "twisted". I was just wondering aloud as to what might explain the disparity in the number of towings. Do you, does anyone have a better hypothesis? (Speculation and hypothesis are quite distinct from "interpretation", of course.)

I've been towed once in the last couple years (Feb 2011 is when I got my Volt). I had a flat tire (no spare and not fixable). I've read about several flat tires. Overall I'm very happy with the tires and their performance in the summer, spring/fall (rain), and winter snow. I just heard the other day that a person always trying take short cuts to reduce their miles (to stay on battery). They claimed several flats based on where they were driving and decided to take more normal routes instead.

 

[RegGuheert]

Do you, does anyone have a better hypothesis?

I don't have a better one, but I will offer a different one: Perhaps this particularly tow truck does not get called when people call for Nissan's towing service which is included with the LEAF. (Or was your tow scheduled through Nissan's service?)

 

[RegGuheert]

Here is a spreadsheet showing every trip taken in our LEAF in the past four months, from 1DEC2012 until 31MAR2013. Unfortunately, this is all the Carwings data that I have. I have added summations at each point an excursion was completed and the car was charged to sum up the kWh used and the miles driven. These summation rows have an "S" in the column labeled "Trip ID".

I have also added two columns. One column is for the calculated DOD what would have occurred for a brand new 2011 Nissan LEAF and the other is the calculated DOD that would have occurred for a brand new 2011 Chevy Volt. The DOD on the Volt column is limited to 80% since what I read is that the Volt's ICE starts at 22% SOC and begins charging at around 20% SOC.

The DOC calculation assumes that each vehicle is charged to full just before the trip, for which I use 94% for the LEAF and 85% for the Volt. I also assume that a Volt would have used the same number of kWh as the LEAF for the trips. Battery capacities are assumed to be 24kWh for the LEAF and 16kWh for the Volt. Available battery capacities are assumed to be 21 kWh for the LEAF and 10.5 kWh for the Volt. No degradation has been used because I do not know how degraded our LEAF battery is and no one knows how degraded any Volt battery is.

In any case, this spreadsheet gives me an idea of the benefits of having a larger battery for OUR daily driving. What I see are the following:

- EVERY trip in the Volt would have resulted in a higher DOD than in the LEAF had we always charged to full.
- A Volt would have experienced 26 trips to 80% DOD within the past four months.
- The maximum DOD for the LEAF during the past four months would be about 73.5%.
- Average DOD for trips in the Volt would be 56% while average DOD for the LEAF would be about 37%.

In reality with our degraded LEAF and actual planning, there was one 90% DOD in the LEAF in March 1 due to the car not being charged for a trip. There were also no more than about four visits to LBW, but no VLBW during this period. Our LEAF has been to VLBW four times in its life but never more than one mile beyond that point.

So, can the SOC limits and TMS of the Volt make up for a higher average DOD and ~75 trips to 80% DOD each year combined with a higher peak discharge rate of over 6C and higher average discharge rate on every cycle? It certainly can in very hot climates, but I seriously doubt it can make up that deficit in OUR climate. The larger LEAF battery can degrade a long way before too many of our trips need to migrate to a different vehicle.

I will caution anyone who may conclude that we would have burned more gasoline if we had a Chevy Volt since there are trips in other ICE and hybrid vehicles which are not included here. It could even be true that we could have driven more EV miles in a Chevy Volt than we did in our LEAF, but I doubt it. There is no way to be sure either way.

For those that are interested, I have updated the the spreadsheet to include all trips through 31May2013. That is a full six months of trips. During this time, it appears that a brand new Volt would have experienced a total of 38 80% DOD events. In other words, in our driving regime, it would have experience about 100 80% DOD events during the 15 months we have owned our LEAF. According to the spreadsheet, the LEAF battery would have experienced none. In reality, our LEAF battery was already somewhat degraded when we got it and we have did not always following the specified charging regime used in the spreadsheet. Still, our LEAF battery has been to LBW fewer than 10 times and to VLBW fewer than 5 times during that period. It has also been stored at a lower SOC than a Volt battery would have been during 99% of that 15 months.

My opinion still stands: Barring some significant chemistry difference between the batteries in the two cars, I expect the LEAF battery will last longer in my application than the Volt battery could. As stated repeatedly upthread, this is DEFINITELY a case where YMMV!

 

[JeffN]

Here is a spreadsheet showing every trip taken in our LEAF in the past four months, from 1DEC2012 until 31MAR2013. Unfortunately, this is all the Carwings data that I have. I have added summations at each point an excursion was completed and the car was charged to sum up the kWh used and the miles driven. These summation rows have an "S" in the column labeled "Trip ID".

I have also added two columns. One column is for the calculated DOD what would have occurred for a brand new 2011 Nissan LEAF and the other is the calculated DOD that would have occurred for a brand new 2011 Chevy Volt. The DOD on the Volt column is limited to 80% since what I read is that the Volt's ICE starts at 22% SOC and begins charging at around 20% SOC.

The DOC calculation assumes that each vehicle is charged to full just before the trip, for which I use 94% for the LEAF and 85% for the Volt. I also assume that a Volt would have used the same number of kWh as the LEAF for the trips. Battery capacities are assumed to be 24kWh for the LEAF and 16kWh for the Volt. Available battery capacities are assumed to be 21 kWh for the LEAF and 10.5 kWh for the Volt. No degradation has been used because I do not know how degraded our LEAF battery is and no one knows how degraded any Volt battery is.

In any case, this spreadsheet gives me an idea of the benefits of having a larger battery for OUR daily driving. What I see are the following:

- EVERY trip in the Volt would have resulted in a higher DOD than in the LEAF had we always charged to full.
- A Volt would have experienced 26 trips to 80% DOD within the past four months.
- The maximum DOD for the LEAF during the past four months would be about 73.5%.
- Average DOD for trips in the Volt would be 56% while average DOD for the LEAF would be about 37%.

In reality with our degraded LEAF and actual planning, there was one 90% DOD in the LEAF in March 1 due to the car not being charged for a trip. There were also no more than about four visits to LBW, but no VLBW during this period. Our LEAF has been to VLBW four times in its life but never more than one mile beyond that point.

.........

I will caution anyone who may conclude that we would have burned more gasoline if we had a Chevy Volt since there are trips in other ICE and hybrid vehicles which are not included here. It could even be true that we could have driven more EV miles in a Chevy Volt than we did in our LEAF, but I doubt it. There is no way to be sure either way.

For those that are interested, I have updated the the spreadsheet to include all trips through 31May2013. That is a full six months of trips. During this time, it appears that a brand new Volt would have experienced a total of 38 80% DOD events. In other words, in our driving regime, it would have experience about 100 80% DOD events during the 15 months we have owned our LEAF. According to the spreadsheet, the LEAF battery would have experienced none. In reality, our LEAF battery was already somewhat degraded when we got it and we have did not always following the specified charging regime used in the spreadsheet. Still, our LEAF battery has been to LBW fewer than 10 times and to VLBW fewer than 5 times during that period. It has also been stored at a lower SOC than a Volt battery would have been during 99% of that 15 months.

Your "DOD" numbers seem goofy.

You say the use of a full charge on the Volt is an 80% DOD which is presumably 100% - 20%.

You say the use of a full charge on the LEAF down to LBW is about 67% DOD (according to your spreadsheet) which is presumably 100% - 33%. However, LBW is actually 18% SOC according to Ingineer (see link below).

In any case, Depth of Discharge (DOD) is normally considered to be the difference between the beginning and end State of Charge (SOC). This charge swing is the primary indicator of charging cycle stress as long as you don't drain the battery much below 20% or charge the battery to near 100%. Lithium Ion batteries have notably better cycle life when the DOD is smaller. Cycling the battery 5 times from 45% to 60% is quite a bit less stressful on the battery than cycling just once from 20% to 95%.

The maximum normal DOD for a Volt is 65% (not 80%) according to GM. For example, 85% - 20% or 86% - 21%.

The maximum normal DOD for a LEAF that is fully charged and driven down to Low Battery Warning (LBW) would be 95% - 18% or 77% (not 67%).*

* http://www.mynissanleaf.com/viewtopic.php?f=8&t=8266" onclick="window.open(this.href);return false;

You said above that the average DOD that you calculated was 37% for the LEAF and 56% for the Volt which is a spread of 56-37 or 19. However, the numbers I noted above indicate that your numbers were biased favorably for the LEAF by 77-67 or 10 and against the Volt by 80-65 or 15 leaving an adjustment spread of 10+15 or 25. If you calculated the LEAF DOD the same way you seem to calculate DOD for the Volt then the DOD driving to LBW would be 82% (100% - 18%) rather than the 66-68% shown in your spreadsheet.

So, a recalculated average DOD would probably show the Volt having an average DOD percentage several points lower than the LEAF.

You also said your LEAF has an average SOC that is lower than the Volt. How do you calculate that? You are assuming the LEAF is charged to 94-95% which is probably more stressful to the battery than the Volt being charged to 85-86% or so. The Volt battery is smaller so any driving will lower it's SOC faster than the LEAF.

 

[RegGuheert]

In any case, Depth of Discharge (DOD) is normally considered to be the difference between the beginning and end State of Charge (SOC).

Not according to Wikipedia:

Depth of discharge (DOD) is an alternate method to indicate a battery's state of charge (SOC). The DOD is the complement of SOC: as one increases, the other decreases. While the SOC units are percent points (0% = empty; 100% = full), the units for DOD can be Ah (e.g.: 0 = full, 50 Ah = empty) or percent points (100% = empty; 0% = full).

...or this battery company called XtremePower:

With regards to a battery, a fully charged battery is at a 100% SOC and a 0% DOD. If it has 75% of its charge, is at a 75% SOC and 25% DOD.

While I am familiar with the usage that you are referencing, I am using it in the manner as cited above.

This charge swing is the primary indicator of charging cycle stress as long as you don't drain the battery much below 20% or charge the battery to near 100%.

Reference please. The qualifiers at the end of your sentence belie the fact that the swing is not the only factor. The DOD is important. How high you go is mainly an issue of storage. Just charging to 94% and immediately discharging is not a big deal.

Lithium Ion batteries have notably better cycle life when the DOD is smaller. Cycling the battery 5 times from 45% to 60% is quite a bit less stressful on the battery than cycling just once from 20% to 95%.

That's basically my point. Except I am adding that the Volt battery experiences more discharges to low SOCs AND it is stored at a higher SOC. While my battery may experience higher temperatures briefly during the summertime, the Volt battery will spend much more time at higher temperatures than the LEAF battery. Our LEAF battery will not get cold enough to be considered harmful.

The maximum normal DOD for a Volt is 65% (not 80%) according to GM. For example, 85% - 20% or 86% - 21%.

Agreed that is the range WHEN NEW. 85% - 20% is what I used in my spreadsheet.

The maximum normal DOD for a LEAF that is fully charged and driven down to Low Battery Warning (LBW) would be 95% - 18% or 77% (not 67%).*

LBW is 18% or 82% DOD per my usage.

You said above that the average DOD that you calculated was 37% for the LEAF and 56% for the Volt which is a spread of 56-37 or 19. However, the numbers I noted above indicate that your numbers were biased favorably for the LEAF by 77-67 or 10 and against the Volt by 80-65 or 15 leaving an adjustment spread of 10+15 or 25. If you calculated the LEAF DOD the same way you seem to calculate DOD for the Volt then the DOD driving to LBW would be 82% (100% - 18%) rather than the 66-68% shown in your spreadsheet.

None of the trips in that spreadsheet used enough energy to discharge a new LEAF battery down to LBW.

So, a recalculated average DOD would probably show the Volt having an average DOD percentage several points lower than the LEAF.

By YOUR definition of DOD, every DOD in the Volt will be 50% larger than in the LEAF.

You also said your LEAF has an average SOC that is lower than the Volt. How do you calculate that? You are assuming the LEAF is charged to 94-95% which is probably more stressful to the battery than the Volt being charged to 85-86% or so. The Volt battery is smaller so any driving will lower it's SOC faster than the LEAF.

Actually, I assume that the LEAF is charged to 80% or lower normally and then charged to 100% just prior to departure. This is exactly how we use the LEAF.

The Volt cannot be used with a similar charging regime since the available energy is 50% of that in the LEAF. As a result, the assumption is that the Volt will be scheduled to be charged to full either immediately or overnight, which will cause it to sit at 85% when new.

Please note that all of the numbers for the Volt should get worse more quickly in my application since the battery should degrade more quickly. (Unfortunately, I purchased a pre-degraded LEAF thanks to the dealer leaving it at 94% SOC for the first six months of its life. C'est la vie!)

 

[DaveEV]

My opinion still stands: Barring some significant chemistry difference between the batteries in the two cars, I expect the LEAF battery will last longer in my application than the Volt battery could. As stated repeatedly upthread, this is DEFINITELY a case where YMMV!

Given that Volts seem to have next to little capacity loss even after two years (or at least I haven't seen any reports of any significant capacity loss) I have to presume that LG does have some sort of special sauce in their batteries which gives them superior calendar life - or GM opens up the SOC range as the battery loses capacity some? Would have to verify full/empty pack resting voltages on a new/old car to be sure...

 

[RegGuheert]

Given that Volts seem to have next to little capacity loss even after two years (or at least I haven't seen any reports of any significant capacity loss) I have to presume that LG does have some sort of special sauce in their batteries which gives them superior calendar life - or GM opens up the SOC range as the battery loses capacity some? Would have to verify full/empty pack resting voltages on a new/old car to be sure...

I agree it has to be one of those two things or a combination of the two. Since it was reported years ago in a feature article written by Lyle at GM-Volt.com that GM designed the BMS to provide the same number of miles as the battery degrades to improve the customer experience, I'll guess they did just that! The idea that LG Chem has a chemistry so advanced that no degradation is seen even after two and a half years of much more severe cycling than the battery in many LEAFs is pretty far-fetched, IMO.

For reference, here are a couple of quotes from Lyle's article:

At the recent Chevrolet Volt launch GM finally let the skeletons out of the closets and exposed all of the Volt’s closely guarded secrets.

As the battery ages and energy storage capacity of the lithium-ion cells degrades, control units will widen the percent state of charge band to continue to deliver the range goal.

 

[surfingslovak]

I agree it has to be one of those two things. Since it was reported years ago by a reputable source that GM designed the BMS to provide the same number of miles as the battery degrades to improve the customer experience, I'll guess they did just that! The idea that LG Chem has a chemistry so advanced that no degradation is seen even after two and a half years of much more severe cycling than the battery in many LEAFs is pretty far-fetched, IMO.

It could be a combination of both, better chemistry and gradual widening of the SOC range. Although it's no silver bullet, they spent quite some effort on the TMS, and have three cells instead of two cells in parallel, which reportedly should play into the aging characteristics as well. I suspect that we will learn soon enough.

 

[RegGuheert]

It could be a combination of both, better chemistry and gradual widening of the SOC range.

Agreed. I edited my post to say the same in parallel with your posting.

Although it's no silver bullet, they spent quite some effort on the TMS, and have three cells instead of two cells in parallel, which reportedly should play into the aging characteristics as well.

We discussed these things upthread. TMS is clearly a win for the Volt in some climates like Phoenix. I suspect it is a liability in Seattle and perhaps it is a wash here. It may also be a win for Chevy in much of CA. As far as three cells in parallel goes, that is really more of a requirement for the Volt than a benefit since it can draw much more power from a battery with 2/3 the capacity.

I suspect that we will learn soon enough.

Because of the TMS and the reported BMS design, I think it may be a couple more years before we start to see range degrading in a Chevy Volt.

But my overriding point remains that the Chevy Volt battery would be cycled much more severely in our application. I do not think any combination of the above factors can overcome this additional cycling and lead to a longer battery life. Let's be clear here: I'm talking about the difference between 10 and 15 years or perhaps 15 and 20 years, if we're lucky.

 

[pkulak]

We have only one car, and we would have gotten the Volt so we could use it for road trips, except that because it has such little interior room, it's no better than the Leaf in that regard. No fifth seat and half the trunk space of the Prius we gave up, and almost a third of the Leaf! With quick charging the Leaf is actually better for family road trips. That truck is fantastic. I forgot how deep a trunk can be with no battery or exhaust under it!

Plus, I'm on a real simplicity kick right now. I love ChromeOS for all the things it gives up, for example. Getting a car that basically crams an entire gas and electric drive train into one just seems like too much. The Leaf has a motor and a battery. Done. I like it.

 

[Deleted member 9549]

We have only one car, and we would have gotten the Volt so we could use it for road trips, except that because it has such little interior room, it's no better than the Leaf in that regard. No fifth seat and half the trunk space of the Prius we gave up, and almost a third of the Leaf! With quick charging the Leaf is actually better for family road trips. That truck is fantastic. I forgot how deep a trunk can be with no battery or exhaust under it!

Plus, I'm on a real simplicity kick right now. I love ChromeOS for all the things it gives up, for example. Getting a car that basically crams an entire gas and electric drive train into one just seems like too much. The Leaf has a motor and a battery. Done. I like it.

Agreed. Well said.
For my family of four, we could barely fit in the volt much less carry anything for a road trip.
And to me, the ICE feels like a crutch. If you're going to go electric just do it already and get a BEV. We kept our ICE for road trips.

 

[fudd246]

I was considering both the Ampera and LEAF when it was time to change my car. My initial leanings were to the Ampera because of its range extender and better looks, but I could never get over the sticker shock. The economics of the Ampera was just unacceptable.

Then, I happened to test drive the LEAF and it was great, zippy, smooth and came with a captivating dash. After a bit of research and reviewing my driving routine, it became obvious that the LEAF could satisfy my needs. The cost savings were obvious. The fact that I would completely give up gas was just icing on the cake.

I agree with those who point out that Nissan should avoid ONLY marketing the LEAF as an eco-friendly vehicle as it has so much more going for it. Ultimately, I choose the LEAF over the Ampera simply based on economics and fun to drive.

 

[skywulf]

We haven't purchased yet; planning to do so within the first quarter of 2014. We looked at both the Leaf and Volt, but the Leaf ultimately won out because it is total electric and the range is perfect for what we need. I'm a gadget geek and like the idea behind the Volt, but as I've gotten older, I've come to like the Keep It Simple Stupid philosophy more and more. The added complexity of the Volt concerns me. The wife loves the idea of not having to pump gas again too! If the Volt had the same battery range as the Leaf, it would have been a closer contest, but as things sit, the Leaf fits our needs perfectly.

Bruce
(soon to be Leaf owner)

 

[mwalsh]

Some interesting stuff on the Volt TMS, shamelessly snagged from gm-volt.com.

Original threads:

for the image: http://gm-volt.com/forum/showthread.php?84778-Battery-thermal-management-Actual-measurements" onclick="window.open(this.href);return false;
for the table: http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band&p=48601#post48601" onclick="window.open(this.href);return false;

Volt battery temperature management system (TMS) modes

Temperature range   | Volt is parked       | Volt is parked       | Volt is powered on
                    |  and plugged in      |  but NOT plugged in  |  (e.g. being driven)
--------------------|----------------------|----------------------|----------------------
                    |                      |                      |
above 122 F         | cooling(1)           | cooling(1)           | car won't run until battery
                    |                      |                      | is cooled below 122 F by TMS(2)
                    |                      |                      |
122 F .. 86 F       | cooling(1)           | cooling(1)           | cooling(2)
                    |                      |                      |
 86 F .. 72 F        | cooling(1)           |                      | cooling(2)
                    |                      |                      |
 72 F .. 68 F        | no action -- ideal temperature band for long-term life
                    |                      |                      |
 68 F .. 25 F        |                      |                      |
                    |                      |                      |
 25 F .. 14 F        | warming              |                      | warming(3)
                    |                      |                      |
 14 F .. -13 F       | warming              |                      | warming(3)
                    |                      |                      |
below -13 F         | warming              |                      | car won't run until battery
                    |                      |                      | is warmed above -13 F by TMS(3)

* Notes:
(1) High temperature cooling will only run if the SOC is >75%.  If the SOC is <75% then there is no action.
(2) At extreme high temps, the ICE may come on to generate power for the TMS to work faster,
  but only if the car is powered on (that is, the ICE won't start by itself, unmanned)
(3) At low temps, the ICE may come on to generate power for the TMS to work faster, and to generate
  power for the cabin heater, but only if the car is powered on (that is, the ICE won't start by itself; it will
  only start once the car is powered on or it receives a remote-start command);  the ICE will shut off once
  it reaches 150 F.  Note that the ICE coolant can not be used to directly heat the battery because the
  battery coolant loop is separate.

 

[essaunders]

I had trouble getting in and out of the volt - plus the very limited rear leg room would have been a pain with kids in the back. Cost was pretty high back in late 2011 too.


that being said, I'm helping my mother shop for cars now. while a pure (non-TESLA) EV won't work for her driving pattern, the volt might. I was actually kinda surprised that (after tax credits) the volt was actually price competitive with the PiP and 'mid tier' regular prius.

 

[mwalsh]

I had trouble getting in and out of the volt - plus the very limited rear leg room would have been a pain with kids in the back.

Agreed on both points. I'm not particularly tall, but my wife is short, so she has the seat raised up quite a bit more than I would. And it definitely doesn't have enough leg room for the boys in the back (they're both well over 6' tall and take size 13 shoes), but I was fine (only 5' 8" with short legs).

 

[Berlino]

When I was shopping in July there was a $4,000 manufacturer's rebate being offered on the Volt in the USA, but not in Canada. When the MY14 Volt was released two months later, GM Canada finally matched the USA price (albeit with the standard Canadian markup.)

So, at the time the Volt wasn't very competitive on price. A few months before, or two months later, I would have had a harder choice.