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Post by jake on Mar 3, 2016 1:02:35 GMT 11
I have edited my original post (below) because after a year of owning the Leaf and reading others observations on battery degradation I have changed my mind in what I think is the order of importance of degradation. I now think it is in this order: 1. Heat 2. Age 3. Leaving the battery at 0% or 100% 4. Cycling Age is a much more significant factor than I thought it was. There seem to be more cycles in the battery then we would ever use in the lifetime of the car so that goes down to the bottom of the list. Original Post: I have thought a lot about this and want to start a new thread on the discussion of what causes battery degradation. I have posted this link before, but I will post it here again. It is a site created by Cadex, an electronic company that manufactures batteries and have done a lot of reasearch into all types of batteries. The Leaf and Tesla cars are specifically mentioned. batteryuniversity.com/learn/article/bu_808b_what_causes_li_ion_to_dieOne of the myths out there is that age is the major cause of battery degradation. The site states that age is definitely a factor, but if you read the rest of the article, there are more significant causes. For instance every battery has a limited amount of cycles - the number of times a battery is charged/discahrged. Cadex admit that a cycle has not really been defined, but we can take it as sgnificant charging and discharging. We also know heat in any form in a LiIon battery is the biggest killer of all. I summarised what I think are the major degradation factors in another post. I repeat them here. 1. Cycling (just using it, charging/discharging) 2. Heat (caused by anything, could be Fast charge/discharging or environmental. 3. Leaving the battery at 100% or 0%. 4. Age (they will degrade by themselves slowly) ALL of these things degrade a LiIon battey. I just think 1,2 & 3 degrade a battery more than 4. This would indicate that the more kilometres you travel, the more degradation you will have, because you have to charge/discharge (cycle your battery) to do the kilometres. If age were a bigger factor than a battery that was older but not cycled should show more degradation than a younger cycled one, and that would mean that soon Nissan would be unable to sell a 2012 Leaf with full 12 bar capacity. (Is my logic ok here?). As long as a battery is stored correctly at 40% charge, then it will always outlast a battery that is being cycled. Depth of discharge is also a factor. Better to do small more frequent charges. One of the great things about the LiIon battery is that is likes shorter charges and discharges that make it well suited to charging through regenerative braking. There is some good news in this. The battery in the Leaf performs very well in lab tests and is built for longevity. If the battery is looked after, you shouldn't see your first bar go under 50,000k. I think i wrote once the average was 20,000k. Iwas wrong about that. I was taking my data from the survey on the American owners forum, and I meant to to say 20,000 miles, but it is more like 30,000 miles travelled before bar loss, which comes close to 50,000k. There is also the survey that Phoebe posted showing that Leafs worldwide had travelled an average of aproximately 50,000k and that 90% of cars still had all 12 bars. We can also expect degradation to be roughly linear. It was thought that degradation might flatten out over time but this is not proving to be the case. Because the worldwide averge of kilometers is going over 50,000K, we are about to see a flood of bar 1 losses which might make people think its age rather than K. The battery is a bit like the ICE. It has a limited life and will deterioate with use (not so much with age) The truth is, no one really knows how long the battery will last. This is new territory for everyone including the manufacturers. We are all trail blazing here. I know there are many people here have lost bars way sooner than they should have, and I can only conclude that those cars have been subjected to the degradation factors listed above more frequently. I am the first to acknowledge that I could be wrong about this, but if you refute what I say, include a link to some research that backs up your claim. I look forward to the debate!
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Post by rusdy on Mar 3, 2016 11:51:42 GMT 11
I am the first to acknowledge that I could be wrong about this, but if you refute what I say, include a link to some research that backs up your claim. I look forward to the debate! Actually, don't fail to mention Prof. Jeff Dahn presentation (which was mentioned in that site). Any geek who is interested (it's an hour long of technical presentation, one must be geek to go through the whole lot, like me ), please sit through the whole presentation. It is enlightening indeed. For example, heat at high SoC is very, very detrimental for 2012 Leaf battery (due to LMO chemistry with no 'secret sauce'). I've mentioned his presentation here before. The youtube link: click here. Also, his opinion, there are lots of improvement can be done for the future, mainly electrolyte selection, which he calls it the 'secret sauce'.
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Post by moyanous on Mar 3, 2016 16:26:08 GMT 11
I can vouch for depth of discharge as the most important factor in battery degradation. I have a couple of laptops whose batteries are completely dead after too many full discharge cycles. One should avoid charging to 100% and then draining your battery to empty. If you need to make several trips during the day with breaks in between then it's better to do smaller charges in between rather than one single big charge for the whole day.
With regards to SOC, I try to keep my leaf at 50% charge overnight. If the battery falls below 50% during the day then I would charge it up to 50% immediately.
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Post by jake on Mar 3, 2016 18:39:47 GMT 11
I can vouch for depth of discharge as the most important factor in battery degradation. I have a couple of laptops whose batteries are completely dead after too many full discharge cycles. One should avoid charging to 100% and then draining your battery to empty. If you need to make several trips during the day with breaks in between then it's better to do smaller charges in between rather than one single big charge for the whole day. With regards to SOC, I try to keep my leaf at 50% charge overnight. If the battery falls below 50% during the day then I would charge it up to 50% immediately. I agree with this totally.
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Post by jake on Mar 3, 2016 18:44:06 GMT 11
I am the first to acknowledge that I could be wrong about this, but if you refute what I say, include a link to some research that backs up your claim. I look forward to the debate! Actually, don't fail to mention Prof. Jeff Dahn presentation (which was mentioned in that site). Any geek who is interested (it's an hour long of technical presentation, one must be geek to go through the whole lot, like me ), please sit through the whole presentation. It is enlightening indeed. For example, heat at high SoC is very, very detrimental for 2012 Leaf battery (due to LMO chemistry with no 'secret sauce'). I've mentioned his presentation here before. The youtube link: click here. Also, his opinion, there are lots of improvement can be done for the future, mainly electrolyte selection, which he calls it the 'secret sauce'. Yes I have seen that. Totally fascinating
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Post by EVangelist on Mar 4, 2016 12:15:04 GMT 11
I can vouch for depth of discharge as the most important factor in battery degradation. One should avoid charging to 100% and then draining your battery to empty. Our typical charging/driving pattern is to charge overnight to 80%, then a typical day will drain that to about 50%. Sometimes we plug in again, sometimes we don't. If we don't, we get down to about 20% or less on the second day, then charge again. So which of these two scenarios would be better for battery life? - Charge to 80% every day. Charge state prior to charging may be as low as 40-50% or as high as 75%.
- Charge to 80% only if current charge is 40% or below (typically 2 days driving).
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Post by moyanous on Mar 4, 2016 13:55:38 GMT 11
I'd say it's better to charge everyday. If you can anticipate that you won't use the car much the next day, then charge but don't go all the way to 80%, by setting the timer to charge for only x minutes. The rule of thumb I use is it takes a little more than 30 mins to charge up a notch.
If you're not sure how much you'll need the car the next day then charge up. The aim is to have the battery at 50% overnight, but it's better to be above rather than below 50% (e.g. 60% vs 40%) because sooner or later you'll have to charge up to 80%, so going from 40% would mean a depth of charge/discharge of 80%-40% = 40%, vs 80%-60% = 20%.
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Post by hieronymous on Mar 4, 2016 14:12:45 GMT 11
Sounds like your typical daily usage is approx. 30% SoC (80->50, 50->20). Also, you are comfortable running down below LBW regularly.
I would, in your situation, decide that I normally didn't need to charge to 80% at all, and would set a timed charge every day of about 2.5 hours, which would give from about 20-50%, using Leaf Spy to adjust the timing initially. If you need more, stretch out your total charge time. Don't plug in if you haven't used the car.
Why? Unnecessary charging results in a higher average charge level overall. Lower is better, and under 40% is better still. More regular smaller charges (lower Depth of Discharge) are supported as better for battery life.
My own charging has followed this pattern for about a year, except that my kms are lower, so I don't charge past 40%. My battery is extremely stable doing this.
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Post by jake on Mar 5, 2016 11:26:23 GMT 11
Smaller more frequent charges is always going to be better than longer less frequent charging. As for what state you should leave your battery for the longest, reasearch suggests that 40% percent is the optimal for longest battery life, but I don't think leaving the charge higher would have any significant difference.
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Post by jake on Mar 5, 2016 11:51:43 GMT 11
I am the first to acknowledge that I could be wrong about this, but if you refute what I say, include a link to some research that backs up your claim. I look forward to the debate! Actually, don't fail to mention Prof. Jeff Dahn presentation (which was mentioned in that site). Any geek who is interested (it's an hour long of technical presentation, one must be geek to go through the whole lot, like me ), please sit through the whole presentation. It is enlightening indeed. For example, heat at high SoC is very, very detrimental for 2012 Leaf battery (due to LMO chemistry with no 'secret sauce'). I've mentioned his presentation here before. The youtube link: click here. Also, his opinion, there are lots of improvement can be done for the future, mainly electrolyte selection, which he calls it the 'secret sauce'. I had another look at the lecture by Jeff Dahn today. It is so interesting, and suggests there is still a lot of potential improvement left in the Lithium Ion batteries. Nissan must have discovered an electrolyte in their "Lizard" battery which makes it pefrom much better in heat, and that also means it would be less likely to be damaged by fast charging. Maybe that's why they took the 80% charge option off in the new Leafs. There was no benefit using the "Lizard" battery. The battery would also have more cycles so 2016 model should last a lot longer than the battery in previous models. It would sure be great if we were able to put that new 30kw battery in our gen 1 Leafs. Nissan engineers have admitted it is technically possible.
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Post by jake on Mar 20, 2016 0:43:12 GMT 11
Here is another interesting article which gives us the best guess to how long our batteries will last as well as some interesting information on battery degradation factors. Depth of discharge is mentioned as an important factor. www.electricvehiclewiki.com/Battery_Capacity_Loss
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Post by jake on Mar 20, 2016 0:56:07 GMT 11
Here is copied section that is a useful guide to get maximum battery life:
For those that already own a Leaf, there are a few things you can do to minimize battery capacity loss: • Keep the state of charge in the 30-40% range (on the Gid meter) as much of the time as reasonably possible. This roughly corresponds to 3-4 fuel bars for a new Leaf. Charge to 80% or 100% right before you need to make a longer drive. • Shallower cycling (DOD) of the battery pack when possible. For example, two cycles of 60% to 30% SOC rather than one cycle of 90% to 30% should be better for the battery pack. • Avoid parking in the sun when possible. Solar loading may increase the yearly average battery temperature by 1.3-3.1 degrees Celsius for a vehicle always parked in the sun (based on studies of the Prius, Media:HEV_Battery_Life.pdf) • Drive and accelerate more slowly and more efficiently. This will have two effects: ◦ Minimizing waste heat (estimated to be 1% at 10 KW power draw, 3% at 30 KW power draw) ◦ Reduced cycling of the battery for the same number of miles driven, which will reduce cycling losses
To monitor the temperature of your battery pack, you can use the Leaf Battery Application.
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Post by jake on Mar 20, 2016 13:19:37 GMT 11
I can vouch for depth of discharge as the most important factor in battery degradation. I have a couple of laptops whose batteries are completely dead after too many full discharge cycles. One should avoid charging to 100% and then draining your battery to empty. If you need to make several trips during the day with breaks in between then it's better to do smaller charges in between rather than one single big charge for the whole day. With regards to SOC, I try to keep my leaf at 50% charge overnight. If the battery falls below 50% during the day then I would charge it up to 50% immediately. After doing some more reading, I have discovered that the current reasearch states that between 30-40% is the sweet spot for LiIon longetivitity. We should keep our batteries at this level as much as possible. Nissan recommends 40% for Leafs in storage but this allows for some natural discharge.
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Post by moyanous on Mar 20, 2016 16:04:55 GMT 11
In light of that I will try to aim for a 40% SOC level overnight. I wouldn't want to go for lower than that because you won't have much room to move if you need your leaf for unexpected errands. Also if you need to regularly charge to 80% then letting it discharge to 40% instead of 50% would mean a higher depth of discharge.
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Post by moyanous on Mar 20, 2016 16:13:58 GMT 11
Here is another interesting article which gives us the best guess to how long our batteries will last as well as some interesting information on battery degradation factors. Depth of discharge is mentioned as an important factor. www.electricvehiclewiki.com/Battery_Capacity_LossAccording to this my usage pattern and environmental factors match Nissan's test conditions for the Leaf: 20000km per anum and battery temperature between 5 bars (winter) and 6 bars (summer) (I'm in Perth), so I should expect to have my battery degraded to 80% in 5 years and 70% in 10 years. I would be very happy with that because I think ICE cars' efficiency also degrade by similar amounts. I'm currently at 24000km and still with full 12 bars of juice.
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Post by lesmando24 on Mar 20, 2016 20:30:22 GMT 11
I have similar temperatures, and at 98,200km, my July 2012 LEAF has lost 3 bars of capacity (72.5%). I think the next bar will go about 110,000km (66.25%). Will see what Nissan can provide as a replacement pack after the warranty expires, as I don't really want to repair the current battery. I would like the newer chemistry 24kWh battery.
les
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Post by jake on Mar 21, 2016 10:12:06 GMT 11
Ambient temperature is a much bigger factor than I realised. Tasmania would be the best place to drive a Leaf. The battery would last a long time with their climate.
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Post by stewartm on Mar 21, 2016 12:30:42 GMT 11
I have noticed that my French Leaf(feuille) in a much cooler climate has no loss of bars with high km's. Must be the cool winter storage, and summer max of 28 which is a 'hot' day according to the locals.
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Post by jeffjl on Mar 21, 2016 15:04:58 GMT 11
Ambient temperature is a much bigger factor than I realised. Tasmania would be the best place to drive a Leaf. The battery would last a long time with their climate. What they make up with the cooler temperatures would be written off due to the hilly nature of Tasmania and the increased current draw from the battery on the up hills.
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Post by moyanous on Mar 21, 2016 16:20:11 GMT 11
And what about the case in the UK where a leaf used as a cab still had not lost one bar after clocking 160000 miles and after many fast charges.
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Post by hieronymous on Mar 21, 2016 16:50:56 GMT 11
If you are referring to Leaf "Wizzy" at C & C Taxis in Cornwall, she had done 130,000 miles by the beginning of Dec 2015, and had lost 1 bar. Was bought new in July 2013.
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Post by empowerrepower on Mar 21, 2016 22:32:26 GMT 11
In light of that I will try to aim for a 40% SOC level overnight. I wouldn't want to go for lower than that because you won't have much room to move if you need your leaf for unexpected errands. Also if you need to regularly charge to 80% then letting it discharge to 40% instead of 50% would mean a higher depth of discharge. Although I'd like my battery to last, I think aiming for a 40% SOC level doesn't allow for a very flexible car, as that would only give me 40 km. I'm just keeping my fingers crossed that better and more affordable batteries will be available in a few years.
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Post by jake on Mar 22, 2016 0:52:49 GMT 11
In light of that I will try to aim for a 40% SOC level overnight. I wouldn't want to go for lower than that because you won't have much room to move if you need your leaf for unexpected errands. Also if you need to regularly charge to 80% then letting it discharge to 40% instead of 50% would mean a higher depth of discharge. Although I'd like my battery to last, I think aiming for a 40% SOC level doesn't allow for a very flexible car, as that would only give me 40 km. I'm just keeping my fingers crossed that better and more affordable batteries will be available in a few years. Yes I agree, I actually don't keep my battery there for that reason, there are many times when I have to unexpectedly use the car. It's just good to know where the sweet spot is, so if you have a choice about what state to leave the battery in, you can aim for it. It's just about making the battery last as long as possible.
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Post by jake on Mar 22, 2016 12:22:56 GMT 11
Ambient temperature is a much bigger factor than I realised. Tasmania would be the best place to drive a Leaf. The battery would last a long time with their climate. What they make up with the cooler temperatures would be written off due to the hilly nature of Tasmania and the increased current draw from the battery on the up hills.
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ant
EV Enthusiast
2012 Leaf, EV enthusiast, AEVA WA Secretary
Posts: 43
LEAF OWNER?: Yes
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Post by ant on May 3, 2016 18:06:01 GMT 11
Here is another interesting article which gives us the best guess to how long our batteries will last as well as some interesting information on battery degradation factors. Depth of discharge is mentioned as an important factor. www.electricvehiclewiki.com/Battery_Capacity_LossAccording to this my usage pattern and environmental factors match Nissan's test conditions for the Leaf: 20000km per anum and battery temperature between 5 bars (winter) and 6 bars (summer) (I'm in Perth), so I should expect to have my battery degraded to 80% in 5 years and 70% in 10 years. I would be very happy with that because I think ICE cars' efficiency also degrade by similar amounts. I'm currently at 24000km and still with full 12 bars of juice. I'm also in Perth, bought 2012 Leaf 3 months ago with 1 bar already gone, 15 000km on the clock. Shoulda done a bit more research before purchase - I think because it was a demo, sitting in a hot car yard, probably at 100% all the time, might have done the battery damage although it would appear ( leaf spy pro via ELM27) not to have hit any cells specifically, just overall degradation. My imiev actually improved after a few fast charges, kinda "kicked" it to have about 10km more range so hoping similiar for leaf.. false hope most likely At the moment, don't think I have more than about 120km of real range at best at 80kmh. GOM drops from +-130km (D) 145(Eco) pretty darned quickly and so its not to be believed I reckon.
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Post by EVangelist on May 3, 2016 19:39:34 GMT 11
At the moment, don't think I have more than about 120km of real range at best at 80kmh. GOM drops from +-130km (D) 145(Eco) pretty darned quickly and so its not to be believed I reckon. Welcome to the Leaf Forum, ant! If you search one of my old threads on the GOM, I pretty much dissed it. Now that I am used to the car I rely on the number of bars of charge left not the GOM, although I almost never test the Leaf's range as I don't drive very far daily and plug in every night regardless. I lost my first bar at 11Mm but I haven't noticed much real reduction in range. In the early days the GOM used to show 130+ km on ECO when 80% charged, now after one bar loss it sometimes shows 120+ but usually 110+. And yes it dies really quickly once you start driving, but it's always done that for me, even when the car was "new" (18 months ago). My commute to work is about 17 km but the GOM decreases almost double that - showing 80 to 90 km range once I get there. But the return journey is nowhere near as bad, and the roundtrip is much closer to GOM estimate (but still out by about 10-20%). I estimate my "real" reduction in fully charged range by that 1 bar loss is about 10% or 15km. My understanding is that subsequent bar loss should come in increasingly spaced out intervals. The initial degradation is the fastest. A few here have lost their second bar, I think one has lost their third?
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Post by moyanous on May 4, 2016 15:50:55 GMT 11
According to this my usage pattern and environmental factors match Nissan's test conditions for the Leaf: 20000km per anum and battery temperature between 5 bars (winter) and 6 bars (summer) (I'm in Perth), so I should expect to have my battery degraded to 80% in 5 years and 70% in 10 years. I would be very happy with that because I think ICE cars' efficiency also degrade by similar amounts. I'm currently at 24000km and still with full 12 bars of juice. I'm also in Perth, bought 2012 Leaf 3 months ago with 1 bar already gone, 15 000km on the clock. Shoulda done a bit more research before purchase - I think because it was a demo, sitting in a hot car yard, probably at 100% all the time, might have done the battery damage although it would appear ( leaf spy pro via ELM27) not to have hit any cells specifically, just overall degradation. My imiev actually improved after a few fast charges, kinda "kicked" it to have about 10km more range so hoping similiar for leaf.. false hope most likely At the moment, don't think I have more than about 120km of real range at best at 80kmh. GOM drops from +-130km (D) 145(Eco) pretty darned quickly and so its not to be believed I reckon. I've posted in another thread that i have since lost my first bar at 25300k.
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Post by hieronymous on May 4, 2016 20:06:12 GMT 11
My understanding is that subsequent bar loss should come in increasingly spaced out intervals. The initial degradation is the fastest. A few here have lost their second bar, I think one has lost their third? First bar loss is 15%, subsequent bar loss is 7.5% each, so the next couple of bars can each be lost quite quickly compared to the first. Some MNL posts discuss a perception that the initial rate of degradation flattens out, but there isn't any data reported to support or refute this...
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Post by rusdy on May 5, 2016 17:58:22 GMT 11
I think there will be no resolution on the accurate cause for 2012 Nissan Leaf batteries (apart from the obvious heat). Since: - No one is conducting 'scientific experiment' using the exact battery (who wants to pay?);
- No one is using this exact battery chemistry anymore (I'm sure Nissan has upgraded since then);
- The SOH via the car itself is a mere 'prediction'.
For the last bullet point above, here is my point: Heck, I can't even trust the SOH reading from LeafSpy anymore (not the LeafSpy fault, it's simply reading the prediction from the car's computer). The only reliable way to know the SOH is to fully-charged to fully-discharged cycle. Oh well...
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Post by Feng on May 5, 2016 18:23:50 GMT 11
I always thought part of it was temperature dependent. I found mine decreases over summer and creeps back up a bit in the cooler months. A few days in the sun would bring down the SOH and a weekend in the underground garage would bring it back up, etc. Your graph seems to suggest that too.
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