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Tuesday, June 11, 2013

When 94 no longer means 94

When I first got the car I could achieve 100 miles per charge if I drove efficiently. However those days are gone unless I drive very slowly and accelerate gingerly. No thanks, I'll live with the lower range!   :)

The range of an electric vehicle is impossible to explain in a single number. The EPA range rating is the simplest way to offer the public an estimate of what to expect form the car and also so it can be compared to other electric vehicles.

However as I have tried to explain in past blog posts, range is a moving target. There are so many factors that can influence how far the car can go like speed, driving style, ambient temperature, topography of your route and many others that's it becomes difficult to really explain to someone how far the car can go on a charge. And that's problematic. It's usually one of the first things people ask me when we talk about the ActiveE. While I want to be as descriptive as possible, I also realize I can't spend to long harping on how different conditions can influence the range because that scares people. Well now I'm going to make it even more scary.

Up until now I have only focused on the outside influences that can effect range; now I'm going to talk a bit about the car itself. I've had the ActiveE for about 17 months now, I'm closing in on 50,000 miles and I've recharged it 1,125 times. In other words, it's no "Spring chicken" anymore, and the battery is showing signs of reduced capacity which means reduced range. For example, in the month of May in 2012, I averaged 96.51 miles per charge, but in May of 2013 I averaged only 83.19 miles per charge. However it wouldn't be fair to only only look at the average range. My consumption rate(my personal driving efficiency or how many miles I drive per kWh's used) was much lower in 2013 so I was driving less efficiently which would account for some of the drop in range by itself. In May of 2012 I had a 3.53 mi/kWh rate and in May of 2013 it was down to 3.27; no doubt due to my late night, highway driving at higher speeds. Still, if I adjust the consumption rate based on the current available battery capacity I would have averaged 89.4 miles per charge instead of the 83.19 that I averaged, which is still a 7% loss of range from May of 2012.

A 7% annual loss of range would be very bad, but you must remember I'm not the average driver. From May 1st, 2012 to May 1st, 2013 I put 35,229 miles on the car and recharged it 822 times. That's probably about equivalent to what an average driver would need two years to do, if not longer. My car lost 7% of its range in that time, which is in line with what industry experts estimate, an approximately 3% annual loss of battery capacity. So actually the EPA rating is simply a snapshot of the approximate range expected when the car in brand new. The car is only new once, and the battery pack immediately begins to degrade, albeit at a very slow rate that isn't even measurable for many months unless you had sophisticated instruments that could measure capacity.

So if you lose about 3% of your battery capacity annually, how long before you need to replace the battery? That will depend on your personal driving needs. Lets say your EV have a 94 mile EPA rating like the ActiveE. If you lose 3% of the range annually your "average" range may look something like this:

Year 1:  94 Miles per charge
Year 2:  91
Year 3:  88
Year 4:  86
Year 5:  83
Year 6:  80
Year 7:  77
Year 8:  74
Year 9:  72
Year 10: 69

At what point does the car fail to function as acceptable transportation for you? One thing for sure that will help immensely is if you can arrange to have charging available at your place of work. Personally I believe the auto manufacturers would be wise to partner with large corporations and help them offset the cost of installing charging stations at their campuses. Having the ability to plug in at work will allow many people that wouldn't otherwise consider an EV do so. Plus it would alleviate any concern that the people may have that in three or four years their EV may no longer be capable of the round trip to work. Of course increasing the amount of other public charge points will be helpful also, but workplace charging is by far the most important place to plug in after ones home. I believe manufactures should provide prospective buyers a guideline like above, perhaps it could even be custom tailored to the customers driving demands, climate they live in and consider other factors that effect range also. This would help the customer understand what to expect from the car.

Remember the above figures are only to be viewed as a basic guideline. There are many other factors to consider like how well you care for your pack, where you live, plus there are different battery chemistries used in EV's and some will fare better in the long term than others. Will large format li-ion cells that BMW(and just about all other major EV manufacturers) uses outlast the small cylindrical laptop-type batteries used by Tesla? I'm not sure anyone really knows that answer yet. I do know a lot has to do with how well the thermal management system maintains the proper temperature of the pack, since excessive heat is really the biggest enemy to long battery life.  Many people say leasing an EV is a smart decision now because there are still so may unknown factors that could negatively influence the future value of an EV and NADA resale values of used EV's tend to confirm that. I'm typically not a supporter of car leasing, but in this case I think it may be a smart decision if you can get a decent lease deal on the EV of your choice. I hope BMW comes out with a strong lease offer on the i3, and really believe the lease offer may hold the key to whether or not they hit their targeted sales goal. For people interested in purchasing an i3 a strong warranty that covers not only manufacturing defects but also battery capacity is also essential. I've written before that I feel a 5 year, 75,000 mile battery capacity warranty that guarantees at least 70% capacity would help ease concerns that the car will not rapidly lose its range and leave the customer with a vehicle that can no longer deliver the range needed for daily use.

I don't want readers to get the impression I'm not still optimistic about the adoption of electric vehicles, because I certainly am. I am completely convinced that plug in electric vehicles are here to stay and that we will only see more and more of them every year. However that doesn't mean there isn't along way to go in educating the public about what to expect from an EV and until the education improves, EV's will continue to be fringe, niche cars. In fact, I believe one of the reasons many people aren't considering one now is because they know so little about them so they are a bit afraid of them. That plus the fact that there really isn't a great crop of plug in offering. There are some good EV's out there like the Model S, the Volt and the LEAF, but very little otherwise. Once more manufacturers like BMW get in the EV game and more compelling plug in models are brought to market, interest in these cars will certainly increase. However interest alone isn't enough. Offering solid warranties, attractive lease deals and having thorough information available about what to expect from the car over its lifetime is key to selling them. Many people are genuinely interested and I talk to them every day,  but they need that final push to be convinced they aren't making a mistake. 


  1. Interesting stuff tom. Much to consider here. This blog has information I don't find anywhere else thank you. Does Nissan provide information on battery life expectancy and replacement cost up front?

  2. This is an example of why electric vehicles will never be accepted. Who would want to buy one if they don't know how far they can safely drive and how long the battery will last? I can get 200,000+ miles on my engine and still drive it as far as I could the day I bought it.

    1. The purpose of the post is really along the lines of your question: "Who would want to buy one if they don't know how far they can safely drive and how long the battery will last?" I agree if the customer isn't informed most will be reluctant to buy an EV. Manufacturers need to provide detailed information that explains what they should expect from their car and battery - and then back it up with a strong warranty.

      I'm not going to touch the comment about your engine lasting 200,000 miles. I could do a whole blog post on how much it will cost you to maintain your ICE for that long.

    2. I would buy an EV.

      Because I have kept cars greater than 200,000 miles in the past and currently have a BMW X5 with greater than 120,000 miles in my Hybrid garage.

      However, how much does a new transmission cost on a BMW? Expensive (I replaced one on a 3 series I no longer owned for $2,500 third party ($4,000-$5,000 at the dealership)).

      How much is gasoline on a BMW (always requires premium)? Let's call it cheap at $4.00 a gallon right now.

      How much are the regular OIL SERVICE intervals for an older BMW, at least $500-$1000 at the dealership a year.

      So, all else being equal, if it turns out that the battery pack on an i3 is (pro-rated based on Tesla publishing a $12,000 figure for the 85kwh (about 4 times the energy of approx 20kwh i3)) is approximately $3,000 or if we were to mark that up 33% to $4,000.

      So, those figures are very similar to a new transmission ALONE and the regular "OIL SERVICE" Intervals on a BMW that is past its new vehicle included service.

      EVs require less maintenance than my ICE cars.

      As I've advocated in the past, regardless of what type of vehicle (ICE or EV) one drives, put aside some money to maintain the vehicle. It just turns out that you're saving more with the EV, and I would hasten to guess that what you are saving can buy your replacement battery when the time comes.

  3. Tom,

    Thanks for always being so precise. I'm not the "average" driver as well and have noticed the same effects (I don't keep detailed logs like you do) at around 35,000 miles driven in 15 months of driving my ActiveE in mostly freeway driving.

    I obviously feel that the offer from BMW for battery warranty to be closer to the Tesla one presented of 8 year unlimited warranty for the 85kwh pack should be adopted for ANY BMW i product. Tesla is gunning for the upper end of the automotive business and BMW is already there. Anything less (even the Tesla 65kwh warranty of 125,000 miles) is just that, less.


  4. "if you lose about 3% of your battery capacity annually" ... Tom I think you are being WAY too conservative here. Manufacturers have said that battery capacity loss is NON-LINEAR, in this case meaning it loses at a quicker rate at first (like the 3% you've seen) but then levels off. Obviously that then wildly affects your extrapolation to later years. I realize that you caveated all this at the end but I think you are really overdoing it with your extrapolation. Still love your blog though :)

    I'm 2.5 years into my Chevy Volt, and I've seen mixed results regarding capacity loss. I have seen NO loss of range in warmer weather, but have seen a little bit of loss in colder weather. However I haven't kept records like you, so I'm not sure about the winter numbers -- those may be no-loss as well!

    1. Hey Chris,

      The Volt uses MUCH less battery percentage than a pure electric does Chris so it will be years before you really see any noticeable difference in capacity with a Volt. I think the Volt only uses about 70% of it's 16kWh pack so it has to degrade quite a bit before you will notice much capacity loss. Most pure electrics use about 90% of their capacity so you will see the capacity loss much earlier. Your Volts battery is definitely degrading, you just can't see it yet.

      I've now driven over 120,000 all electric miles and have recorded every single day and every time I've plugged in (I have over 2,600 entries - yeah I'm a geek!) so I have a very good sample that includes two totally different battery cells and chemistry. I have also talked with EV electrical engineers from a few different companies as well as battery techs. I certainly don't claim to know everything about this stuff, but I can tell you others that are experts have also concurred that about 3% degradation per year for the 'average' EV driver should be about what to expect, conditions permitting of course. If you have real info or links to the contrary, please send them to me. I can't have too much info on this!

    2. Also, in the winter your range is lower because the battery's chemical reactions occur more slowly, so when a battery is used at a low temperature less current is produced. The battery capacity is only temporally lowered, you haven't really lost that capacity, you just can access it until the battery warms up.

  5. I've also seen reports of about an expected 2% to 3% annual loss of capacity for these lithium ion packs under normal use. The Nissan LEAF has had much more accelerated capacity loss in hot regions though and have lost 30% in two years in some cases. So after 7 years the pack will drop under the magic threshold of 80% which is considered by many to be the end of life for automobile use. I would like to know the replacement cost before buying, or perhaps leasing as you recommend may be the way to go until there is ample long term battery results to compare to.

    Be well,

    1. Hi Will. It's important to note that the owner has a LOT of control over the battery life. Frequent deep discharges and allowing the battery to fully charge and then sit for an extended period while fully charged will accelerate degradation.

      Yes the LEAF is experiencing difficulty in hot weather regions, but it doesn't have a proper thermal management system to keep the batteries cool and heat is your #1 enemy. The ActiveE and i3 (along with just about every other modern EV) has a thermal management system to maintain proper battery temperature. This is definitely the LEAF's Achilles heal.

  6. BMW has released the first teaser video of the 2014 i3.
    Set to be unveiled on July 29th, the i3 will closely resemble the concept that debut at the 2011 Frankfurt Motor Show :) Great urban car!