|
|
Post by hieronymous on Jun 4, 2015 20:55:50 GMT 11
There can't be many topics on Leaf forums that attract more posts than "how long to first battery bar loss". A major gripe is always that some Leafs travel big distances without bar loss while others lose a bar at a low odo reading. What is surprising is that owners continue to link distance travelled with battery degradation, when such a linkage is completely erroneous.
EV drivers with few exceptions have been /still are ICE car drivers too. Personal experience plus the culture of vehicle ownership tells us that typically, a conventional vehicle "wears out" the further you drive it; at high odo readings major overhauls are needed to keep the vehicle road-worthy and reliable. What this actually means is that the drive-train (ICE, gearbox etc) steadily wears, and we have come to expect that a high odo reading may mean a risky purchase without evidence of overhaul.
So we Leaf owners are transferring this notion to our EV's because it is part of the vehicle owing culture. The problem is that we are transferring it to the longevity of the HV BATTERY, instead of to the Leaf drive-train (electric motor, reduction gearing) which would be the valid comparison to make.
There are many kinds and sizes of batteries but they share common characteristics - in particular they all have a short life, and they start degrading from the date of manufacture. All cars including ICE cars have an auxiliary battery. When we think about the life of an ICE car battery we don't think of the odo reading; we are used to such batteries lasting about 3-5 years and we think of how many years since last replacement. If we DID think about odo readings it would clear that some vehicles travel very big distances in 3-5 years e.g. taxis, while many of us only do a short commute plus some weekend running around, but taxi auxiliary batteries are still likely to last the same sort of time. We therefore do not make a connection between battery life and odo readings in an ICE car, and we should not be making this comparison for a Leaf.
The Leaf HV battery has a very large capacity in contrast to an auxiliary battery, so it will continue to do the job it is designed to do for much longer than 3-5 years UNLESS the owner is looking for maximum range from Day 1. The key thing to remember, however, that it IS steadily degrading, and it will typically show signs of degradation in 3-5 years (as Nissan tells us), and what we Aussie and Kiwi owners have to remember is we have bought 2012 vehicles and it is now 2015. So we must expect, and this what we are seeing, that some forum owners will be seeing first bar loss now, irrespective of odo reading, while all the rest of us will gradually see our Leaf reach the same point over the next couple of years or so. If all forum owners used Leaf Spy or similar, and reported their battery reading every month, it would be clear that all our cars are travelling down the same battery path. A bar loss can be a shock because the Leaf doesn't give us any warning, and the dash bar display is poorly designed. But it is only one percentage point and our cars in our climate most likely will continue to perform entirely satisfactorily for many years to come.
|
|
|
|
Post by Phoebe on Jun 4, 2015 22:20:57 GMT 11
If you look at another topic you'll see we all understand that how long our key batteries last has nothing to do with how far we have driven our LEAF, but everything to do with how old they are. Funny that we get confused with our engine batteries, probably because things like the weather and quick charges may make a difference.
|
|
|
|
Post by EVangelist on Jun 4, 2015 23:35:54 GMT 11
|
|
|
|
Post by hieronymous on Jun 5, 2015 9:34:38 GMT 11
If you look at another topic you'll see we all understand that how long our key batteries last has nothing to do with how far we have driven our LEAF, but everything to do with how old they are. Funny that we get confused with our engine batteries, probably because things like the weather and quick charges may make a difference. Yes, it is certainly useful to look at how we use our cars and under what conditions to see how that might impact on battery longevity. Any discussion about car auxiliary battery life tends to suggest the following, : The real reason no two batteries perform the same is because they are subjected to different environments. Ambient (air) temperatures have significant effects on car batteries and temperatures vary around the globe. If your Leaf commonly shows 6 temperature bars in summer and/or 4 temperature bars in winter then this is likely to impact more negatively on battery life. The biggest reason batteries perform differently is due to users. Users have their own unique patterns such as frequency of charging the car, starting the car, driving distance, driving speeds, non-driving durations and accessory use both when the car is running, and not running. It is notable that vehicles running all day, every day, such as taxis, typically get a long life from the vehicle component, including the batteries. Car batteries will self discharge when not in use. In general a lead-acid auxiliary car battery self discharges at a rate of three percent per month. This rate increases when ambient temperature exceeds 20 degrees Celsius (68 degrees Fahrenheit). The more cycles a lead acid car battery has experienced will also start to reduce the capacity of the battery. The Leaf HV battery is not the same as an auxiliary battery, but all batteries generally share the same characteristics though at different rates. |
|
|
|
Post by philcanberra on Jun 5, 2015 13:04:50 GMT 11
My LEAF usually shows 6 temp bars (sometimes 7 and once 8) during summer and 4 or less in Winter in Canberra and I still have 12 bars and 38,000km.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 5, 2015 14:53:03 GMT 11
|
|
|
|
Post by markrmarkr on Jun 5, 2015 14:58:20 GMT 11
There are other things apart from age that effect the life expectancy of our batteries. The big one is depth of discharge. Running the car right down to zero is not recommended, as it is the quickest way to kill your traction pack. This is similar to the effect of leaving your lights on for a Lead acid 12 Volt battery. Completely discharging a 12 Volt battery multiple times can kill it, even if it is new.
A weakness of the top balancing philosophy used by most EVs, including the Leaf, is that the bottom is therefore unbalanced. So when you completely discharge the pack there will always be one cell which is more discharged than the rest, and there is a danger that this cell will be damaged.
|
|
|
|
Post by jeffjl on Jun 5, 2015 16:34:29 GMT 11
Yes Hieronymous, the batteries are three years old when the vehicle is bought and there is a time degradation of them. From all my reading though the biggest expected degradation of the batteries is due to cycling of it. The best indication of cycling is the km your vehicle has traveled.
All our vehicles in Australia were brought across at about the same time so all vehicles will have similar time degradation of them. Yes there will be some variation between different batteries even if stored next to each other but the wide variation between the best and the worst is well outside what this variation could possibly explain.
That we can confirm on this forum that two of the three known here (and I am told by the dealer that I bought my car from he knows of three others which he has been dealing with) on this forum are in Perth it is not unreasonable that the relevant batteries have been abused in their storage here in Perth.
I was not expecting 50k out of my vehicle before the first battery bar disappeared but would have more than 9k been too much to ask.
I agree, I think that the battery is degrading in the expected way (and rate) but the battery that was sold to myself ( and the others in Perth) was already significantly degraded. I bought a vehicle which advertised a 25kWh battery. It appears that it was about 10% less. I would not be happy if my employer paid me 10% less than what they said they would and this is similar.
Note. I still think it is a great vehicle.
|
|
|
|
Post by hieronymous on Jun 5, 2015 18:33:18 GMT 11
Yes Hieronymous, the batteries are three years old when the vehicle is bought and there is a time degradation of them. From all my reading though the biggest expected degradation of the batteries is due to cycling of it. The best indication of cycling is the km your vehicle has traveled. Yet the British taxi referred to above by EVangelist has a very high cycle number (by my reckoning 2 Quick Charges a day, and driven approx. 100km per Quick Charge) but is still to lose a bar. So I'm not convinced that cycling produces the biggest degradation, or that therefore the odo reading gives much (if any) understanding of battery state. It certainly seems possible/likely that some Perth Leafs have spent a lot of time sitting out on display in the sun. But for degradation for Leafs typically I would think first about calendar age, then climate (temperature extremes), then charging/discharging frequency, as major contributors. |
|
|
|
Post by hieronymous on Jun 5, 2015 18:44:15 GMT 11
There are other things apart from age that effect the life expectancy of our batteries. The big one is depth of discharge. Running the car right down to zero is not recommended, as it is the quickest way to kill your traction pack. This is similar to the effect of leaving your lights on for a Lead acid 12 Volt battery. Completely discharging a 12 Volt battery multiple times can kill it, even if it is new. A weakness of the top balancing philosophy used by most EVs, including the Leaf, is that the bottom is therefore unbalanced. So when you completely discharge the pack there will always be one cell which is more discharged than the rest, and there is a danger that this cell will be damaged. I have read on the MyNissanLeaf.com forum that research/feedback on Leaf owners use of their cars, shows that a very high percentage are scared of being stranded to the extent that they won't go below LBW. So I suspect that only a few daredevil owners have tried this deliberately. I have never seen VLBW, but my one weak cell shows up at about 2.5 KWh - that's close enough for me. |
|
|
|
Post by hieronymous on Jun 5, 2015 19:30:53 GMT 11
My LEAF usually shows 6 temp bars (sometimes 7 and once 8) during summer and 4 or less in Winter in Canberra and I still have 12 bars and 38,000km. Hi Phil, impressive numbers! I think I have seen in other posts of yours that you were an early adopter and have had your Leaf nearly 3 years, and that your SOH is about 89% at present?? I guess that although your temp bars have ranged widely, it is not for very long; your Canberra weather keeps on steadily changing from season to season? Many of us have had our cars for a short time, so didn't have the opportunity to start with a "full" battery. Mine was at SOH 96% after 26 months in storage; it is hard to draw comparisons when our cars have had such different beginnings. Based on all my reading, your data is what I would hope to see for a 3-year old car steadily putting on 12-13K km's per year and regularly charged. Sounds like it could be quite a while before you lose a bar.... |
|
|
|
Post by jacky on Jun 5, 2015 19:44:27 GMT 11
Yes Hieronymous, the batteries are three years old when the vehicle is bought and there is a time degradation of them. From all my reading though the biggest expected degradation of the batteries is due to cycling of it. The best indication of cycling is the km your vehicle has traveled. Yet the British taxi referred to above by EVangelist has a very high cycle number (by my reckoning 2 Quick Charges a day, and driven approx. 100km per Quick Charge) but is still to lose a bar. So I'm not convinced that cycling produces the biggest degradation, or that therefore the odo reading gives much (if any) understanding of battery state. It certainly seems possible/likely that some Perth Leafs have spent a lot of time sitting out on display in the sun. But for degradation for Leafs typically I would think first about calendar age, then climate (temperature extremes), then charging/discharging frequency, as major contributors. While we are arguing what caused battery degrade, this video may give us and answer www.youtube.com/watch?v=9qi03QawZEkYou only need to watch the first 7 mins to get the answer. |
|
|
|
Post by hieronymous on Jun 5, 2015 21:42:52 GMT 11
Yet the British taxi referred to above by EVangelist has a very high cycle number (by my reckoning 2 Quick Charges a day, and driven approx. 100km per Quick Charge) but is still to lose a bar. So I'm not convinced that cycling produces the biggest degradation, or that therefore the odo reading gives much (if any) understanding of battery state. It certainly seems possible/likely that some Perth Leafs have spent a lot of time sitting out on display in the sun. But for degradation for Leafs typically I would think first about calendar age, then climate (temperature extremes), then charging/discharging frequency, as major contributors. While we are arguing what caused battery degrade, this video may give us and answer www.youtube.com/watch?v=9qi03QawZEkYou only need to watch the first 7 mins to get the answer. This (2013) video illustrates that lithium-ion battery technology is still in it's infancy, that manufacturer's aren't doing proper testing because it takes too long, and that Nissan should have put active thermal management in the Leaf, as other makers have done since. It doesn't tell us anything about what may have happened to any one car to cause rapid bar loss at low km's, or to have no bar loss despite high recycling and high km's. Nissan has sold a lot of Leafs, and most of them are running fine with moderate usage in moderate climates without widespread bar loss. We tend to hear about the extremes. I'll stick with my calendar age, climate extremes, and charging/discharging frequency for Leafs in general. |
|
|
|
Post by jacky on Jun 5, 2015 22:07:46 GMT 11
The degree of degrade is depends on the time the battery exposed to heat.
It will be fine to have no thermal management if the car was not operated in extreme hot or cold weather.
As an owner in Victoria, my car doesn't need thermal management.
|
|
|
|
Post by caskings on Jun 5, 2015 23:36:08 GMT 11
As an owner in Victoria, my car doesn't need thermal management. In the middle of winter, it would be helpful. |
|
|
|
Post by jacky on Jun 6, 2015 8:46:11 GMT 11
In Melbourne, the temperature never go below zero. Even at zero degree, the battery will not suffer any damages. The performance may degrade in low temperature.
In low temperature, thermo management is two edge sword. It improves battery performance by increasing battery temperature but the energy to maintain temperature is coming from the battery itself.
During the snow storm in 2013/14 U.S., one model S owner experienced huge drop in battery range after the thermo management kicks in. The car ended up ran out of juice on a freeway. It proves that the battery thermo management can use a lot of energy in extreme cold.
There is a point thermo management can improve the overall energy for driving from the battery pack but I believe it is below the temperature we have in Victoria.
|
|
|
|
Post by hieronymous on Jun 6, 2015 10:18:02 GMT 11
Thermo management isn't provided for performance (though in some situations it will result in better balanced performance). Its function is to protect the battery from extreme temperatures and thus maximise battery longevity.
|
|
|
|
Post by jacky on Jun 6, 2015 13:39:38 GMT 11
|
|
|
|
Post by jacky on Jun 11, 2015 22:12:51 GMT 11
|
|
