evas2012leaf
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Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 12:06 am

You bought the car with 22,000 miles on it and you don't know how the previous owners drove the car. More than likely they drove it hard and prematurely damaged the cells in the battery pack. We had the same experience with a 2011 leaf that we bought. It was still a great car, but because of being driven hard the cells were damaged and we paid the price for it.
It is important to understand the nature of lithium batteries. Yes, Nissan uses an exotic chemistry, but all in all it is pretty good. The major fault that Nissan has is NO COOLING SYSTEM!!! In fact the battery pack in a leaf is sealed completely! No air can get in to cool the cells and there is no liquid cooling to pull heat from the cells. They cool by convection only! If you are going to drive a leaf you need to keep that in mind or you will continue to damage the cells. Keep an eye on that battery temp. gauge especially in hot weather and be careful how you charge especially with the fast dc chargers. They do raise the temp in the cells that is just the way it works current going through the battery creates heat. I sold my wife's 2011 after she had driven it for a little over a year. She put 18,000 miles on it in about 16 months. It had 9 bars when we bought it, but almost at once it lost down to 8. I taught her how to drive the car and how to charge it and she lost no more bars of battery while we owned it.
Lithium's by their nature do not like to be fully charged. They especially do not like to be charged to 100% and then left there to slowly discharge. On our 2012 we can choose to set the charge timer so that it only charges to 80% and that is what we do for over 90% of our charging. Only if we are going out of town and need the extra range do we turn off the charge timer and charge to 100%. Also keep in mind that lithium's do not like to be discharged below 20%. This will also damage them. Unfortunately the software in the 24kw leaf only reserves the bottom 2kw of the battery pack, this is not enough to prevent damage. If you are going into those two bottom bars of the "fuel" gauge often you are slowly damaging the cells by over discharging them. I have taught my wife to consider those bottom bars as an emergency supply of "fuel" only. Only a couple of times over the last 48,000+ miles has she dipped into those.
When we do go out of town we have to use freeways and 4 lane highways. We have learned to go a little slower and WATCH THE ENERGY SCREEN!!!! If you learn to read that screen it can give you a wealth of information. If you strive to keep your discharge rate down to about 1c (which is the amp rating of the cells) you will not do any damage. For instance if you are pulling 10kw on the screen you are actually drawing about 25 amps (power in watts divided by voltage) which is well under 1c. The lizard pack in my wife's car has 60 amp cells in it. Earlier 24 kw packs had a lower energy density but still over the 25 amp rating. Keep that in mind as you drive. Yes, the car can burn up to 60 or 70 kw, but to do so for any length of time will damage the battery pack badly!

nlspace
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Delivery Date: 06 Jun 2017

Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 6:23 am

Spacedogb wrote:
Wed Nov 13, 2019 3:42 pm
...
I have never quick charged and I always plug when i get home. I charge on 110v and usually activate charge when i get home and only charge to 80%. I have a 8 mile drive to work and usually top back off to 80% while at work on the 110v charger.
i have seen lithium cell datasheets which have a chart showing the fade or decay in cell capacity as a function of the number of cycles, i.e. charge cycles. Tests are typically made using full charge and discharge cycles, but my reading of this data is that every time you plug in to charge counts as a cycle.

My guess is that you are taking life out of your pack by charging for no real reason. There is no need to always maintain 80% SOC and especially not twice a day. You are adding 2 cycles a day where you could probably get by with one or two in a week.

i've never seen a datasheet for laef cells but would think this test was done for them also. It would be interesting to see the graph.

LeftieBiker
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Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 6:57 am

Tests are typically made using full charge and discharge cycles, but my reading of this data is that every time you plug in to charge counts as a cycle.

My reading of it - and I believe that this is the majority opinion - is that partial charges are partial cycles, and charging cycles that stay in the 'sweet zone' of 25-60% count for just a small fraction of a cycle. Charging to 100% and then running it down to 10% - that is a full test cycle equivalent. That is how some Leaf taxis and other Leafs have done so many "cycles" while losing so little capacity.
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cwerdna
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Location: SF Bay Area, CA

Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 6:59 am

Can you please get your units right? Please see viewtopic.php?p=520169#p520169.
evas2012leaf wrote:
Wed Jan 01, 2020 12:06 am
Unfortunately the software in the 24kw leaf only reserves the bottom 2kw of the battery pack, this is not enough to prevent damage.
Energy and battery capacity are measured in kWh, not "kw",
evas2012leaf wrote:
Wed Jan 01, 2020 12:06 am
The lizard pack in my wife's car has 60 amp cells in it. Earlier 24 kw packs had a lower energy density but still over the 25 amp rating.
What are 60 amp cells? Again, battery capacity is measured in kWh. You mean 24 kWh here.

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nlspace
Posts: 239
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charging and capacity fade

Wed Jan 01, 2020 9:09 am

reviewing scientific journals for research findings and conclusions, e.g. washington.edu
Passive SEI layer growth is a major contributor to capacity fade in Li-ion batteries used for EV and PHEV applications. The majority of SEI layer growth will occur during charging. While fast charging creates undesired stress and temperature affects among other degra- dation problems, it will limit the amount of direct SEI layer growth in comparison to slow rates. Additionally, CC-CV charging will increase the amount of charge stored within a battery for a single cycle, but over the entire cycle life of the battery will decrease the total amount of usable energy from the battery for drive cycle cases.

During daily cycling most EVs do not experience a 100% DOD of their batteries. Cycling at smaller DOD from 100% SOC will in- crease the amount of SEI growth per mile driven compared to 100% DOD cycling. However, cycling at small DOD at lower starting SOC (eg. starting at 50% SOC and cycling to 0% SOC for a 50% DOD) will decrease the amount of SEI layer growth when compared to 100% DOD mainly due to the lower battery potential during cy- cling. While cycling at lower SOC may be beneficial for reducing SEI growth, it is not advisable for actual EV and PHEV use be- cause it causes underutilization of the battery capacity over each cycle.

johnlocke
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Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 10:45 am

According to Jeff Dahn, a cycle is a cycle. Partial cycles add up to full cycles. Three 33% to 66% cycles add up to one cycle. The leaf battery is never charged to ultimate capacity (4.3 vdc per cell) anyway. Charging is stopped at 4.11 vdc per cell intentionally. A standard full discharge cycle is 4.3 vdc to 3.0 vdc. In the Leaf the discharge cycle is limited to 4.11 vdc to 3.2 vdc by design. Below 3.3 vdc, there is little power left in the battery and the discharge voltage curve falls off rapidly. Most people never come close to full discharge anyway.

A standard li-ion battery might be expected to last 300-400 cycles at a full discharge cycle. Turns out that for every 70 mv you lower the upper limit, battery life doubles. At 4.11 vdc as the upper limit, you could expect about 1500 cycles before the battery degrades too far to be useful. Leafs actually get that in cool climates. Nissan didn't account for degradation at higher temps though. The lack of a TMS in the leaf battery pack was a cost cutting measure that causes Leafs to significantly degrade in hot weather.

Lowering the upper limit to 4.0 vdc does improve battery longevity somewhat but the effect of lowering the upper limit still further is marginal.
The reason that lowering the upper voltage works to improve battery life is that the anode swells significantly as the battery approaches full capacity which causes mechanical stress.
2016 SV, New battery at 45K mi.
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LeftieBiker
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Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 1:42 pm

johnlocke wrote:
Wed Jan 01, 2020 10:45 am
According to Jeff Dahn, a cycle is a cycle. Partial cycles add up to full cycles. Three 33% to 66% cycles add up to one cycle. The leaf battery is never charged to ultimate capacity (4.3 vdc per cell) anyway. Charging is stopped at 4.11 vdc per cell intentionally. A standard full discharge cycle is 4.3 vdc to 3.0 vdc. In the Leaf the discharge cycle is limited to 4.11 vdc to 3.2 vdc by design. Below 3.3 vdc, there is little power left in the battery and the discharge voltage curve falls off rapidly. Most people never come close to full discharge anyway.

A standard li-ion battery might be expected to last 300-400 cycles at a full discharge cycle. Turns out that for every 70 mv you lower the upper limit, battery life doubles. At 4.11 vdc as the upper limit, you could expect about 1500 cycles before the battery degrades too far to be useful. Leafs actually get that in cool climates. Nissan didn't account for degradation at higher temps though. The lack of a TMS in the leaf battery pack was a cost cutting measure that causes Leafs to significantly degrade in hot weather.

Lowering the upper limit to 4.0 vdc does improve battery longevity somewhat but the effect of lowering the upper limit still further is marginal.
The reason that lowering the upper voltage works to improve battery life is that the anode swells significantly as the battery approaches full capacity which causes mechanical stress.

The above is different from "Tests are typically made using full charge and discharge cycles, but my reading of this data is that every time you plug in to charge counts as a cycle." I don't agree that you just add fractions of cycles, regardless of their 'depth', but I'll admit that it may be right. I don't see anyone agreeing with you that any charge, no matter how short or shallow, counts as a cycle.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
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PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

johnlocke
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Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 5:56 pm

LeftieBiker wrote:
Wed Jan 01, 2020 1:42 pm
johnlocke wrote:
Wed Jan 01, 2020 10:45 am
According to Jeff Dahn, a cycle is a cycle. Partial cycles add up to full cycles. Three 33% to 66% cycles add up to one cycle. The leaf battery is never charged to ultimate capacity (4.3 vdc per cell) anyway. Charging is stopped at 4.11 vdc per cell intentionally. A standard full discharge cycle is 4.3 vdc to 3.0 vdc. In the Leaf the discharge cycle is limited to 4.11 vdc to 3.2 vdc by design. Below 3.3 vdc, there is little power left in the battery and the discharge voltage curve falls off rapidly. Most people never come close to full discharge anyway.

A standard li-ion battery might be expected to last 300-400 cycles at a full discharge cycle. Turns out that for every 70 mv you lower the upper limit, battery life doubles. At 4.11 vdc as the upper limit, you could expect about 1500 cycles before the battery degrades too far to be useful. Leafs actually get that in cool climates. Nissan didn't account for degradation at higher temps though. The lack of a TMS in the leaf battery pack was a cost cutting measure that causes Leafs to significantly degrade in hot weather.

Lowering the upper limit to 4.0 vdc does improve battery longevity somewhat but the effect of lowering the upper limit still further is marginal.
The reason that lowering the upper voltage works to improve battery life is that the anode swells significantly as the battery approaches full capacity which causes mechanical stress.

The above is different from "Tests are typically made using full charge and discharge cycles, but my reading of this data is that every time you plug in to charge counts as a cycle." I don't agree that you just add fractions of cycles, regardless of their 'depth', but I'll admit that it may be right. I don't see anyone agreeing with you that any charge, no matter how short or shallow, counts as a cycle.
I never suggested that any charge/discharge no matter how shallow counts as a cycle. It counts as a fractional cycle. My point is that shallow cycles still add up and that limiting the depth of discharge may not be as useful as some claim and that limiting the max charge to less than 80% may not improve battery life.

In any case, this may be moot if Dahn's research is accurate. Minor changes in the anode composition and electrolyte could result batteries that could last through 3000-4000 cycles with less than 10% degradation. Batteries could outlast the useful life of the cars they are installed in.
2016 SV, New battery at 45K mi.
Jamul, CA
San Diego East County

LeftieBiker
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Re: What am I doing wrong? 2013 Leaf 28k 10 bars

Wed Jan 01, 2020 6:19 pm

You apparently didn't mean what you wrote the way you wrote "but my reading of this data is that every time you plug in to charge counts as a cycle." My feeling is that only substantial charging counts, but this is more gut feeling than based on hard evidence. This opinion is shared by many others in the electric bicycle community, and is based on often long ownership of smaller lithium packs.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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