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gbarry42
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Re: Battery degradation info, 80% vs. 100% daily charge

Tue Jul 12, 2011 1:18 pm

electricfuture wrote:The good news concerning new batteries is that my understanding is that you don't have to replace all of them at once. The battery 4? packs are individually monitored. Thus you could just replace say 20% to bring your range back to the original 100 miles. As time goes on I plan to replace them in stages over a 5 year period starting 8-10 years from now.

I'm afraid it doesn't work that way. The above seems to imply that one module will go "bad" before the others do. If this were to happen in a dramatic way, it would show up sooner than later, and would be replaced under warranty. The Battery Monitoring System, plus all the research that went into the battery, suggests that they won't get out of balance in the first place. And if they did nonetheless, the most difference you could have by changing out one module of 48 would be 1/48 or 2 percent of the total.

Replace 20% of the modules? That would be 10 modules. But if the new ones were at 100%, and the ones you didn't change had 80% capacity, the total capacity would be...80%. That's because they're in series, and the weakest module limits the total. Remember that the BMS can monitor the differences, but it can't modify the current draw pattern from them.
And there goes the first capacity bar! At 24,000 mi on 9/9/2013.
Second bar at 30,500 mi on 2/7/2015.

solartim
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Re: Battery degradation info, 80% vs. 100% daily charge

Tue Jul 12, 2011 2:12 pm

The 4K charges aren't public, that's why they don't show up. Ecotality put one in my garage, and it works fine.

sfosri wrote:In response to a comment:

Ecototality is a scam company..they collected money from DOE to install chargers...they don't have a map of the chargers on their website nor a list...they don't even have an app they announced with big fanfare. This company put out big press releases but nothing really materializes.

I joined the Blink network which belongs to them and there I saw a map with a total of 26 chargers around the whole country...what a joke. They need to be investigated and so do all these companies that are getting lots of our tax money to build charging infrastructure.

wallybucks
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 4:10 am

The best way to keep any lithium ion battery healthy is to avoid low and high charge levels. High level charges are especially damaging if the battery temp is high (that may be why the manual says to avoid charging on Level 3 more than once a day since it makes heat). I have read where damage at high level charge while at an elevated temperature happens regardless if you are charging so do not charge to 100% then park it in extreme heat for an extended time. Low charge is so damaging that lithium batterys MUST have protection to keep them from being completely discharged. Even lithium ion cellular phone batteries have a small onboard computer to protect them from being dischrged less than 20% or overcharded.

The faster the battery is charged or discharged the more damage it does. Avoid level 3 charge and always use the trickle charger that came with the Leaf when you have the time.

If you only use your car to go a short distance every day always keep it between 40 and 60 % charge to extend the life of the lithium batteries.

These tips will not help much per charge cycle but will add up to make a large one over years of use.

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Stanton
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 5:32 am

wallybucks wrote:The faster the battery is charged or discharged the more damage it does. Avoid level 3 charge and always use the trickle charger that came with the Leaf when you have the time.
These tips will not help much per charge cycle but will add up to make a large one over years of use.


I agree with most everything you said save the statement above: Level 2 (220v) charging should do no more harm than Level 1 charging. Charging to 80% using Level 2 on a daily basis should have no long-term negative effects on the battery pack (remember Nissan has already built-in a buffer on the top and bottom ends).
2011 Blue Ocean SV w/floor mats & window tint
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Herm
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 10:11 am

wallybucks wrote:The best way to keep any lithium ion battery healthy is to avoid low and high charge levels. High level charges are especially damaging if the battery temp is high


Some alarming statements from the lithium-ion wikipedia, probably written by a republican oil executive:

http://en.wikipedia.org/wiki/Lithium-ion_battery

"A Standard (Cobalt) Li-ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively.[51] In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge.[52]"

Stoaty
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 3:11 pm

Herm wrote:
wallybucks wrote:The best way to keep any lithium ion battery healthy is to avoid low and high charge levels. High level charges are especially damaging if the battery temp is high


Some alarming statements from the lithium-ion wikipedia, probably written by a republican oil executive:

http://en.wikipedia.org/wiki/Lithium-ion_battery

"A Standard (Cobalt) Li-ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively.[51] In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge.[52]"

That's why Nissan doesn't allow you to charge the battery fully, there is some (unknown) amount of headroom at the top you can't access.
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rwherrick
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 3:47 pm

Stoaty wrote:
mark13 wrote:I charge the leaf 100% every other day..I don t remember the salesmen ever saying to only charge at 80% to save the battery for a extended life..

I wouldn't pay attention to the salesmen. Nissan didn't name the 80% charge "Long Life Mode" for nothing. It's right there in the manual. However, we don't know exactly how much this will prolong battery life.


I believe I can shed some light on this question.

1) One of the Nissan Engineers that I met questioned why I wasn't using the 80% charge feature, given that I have a short commute. He claimed that Nissan's testing shows that only charging to 80% will double the battery pack life on average, when compared to fully charging the battery pack. This was the first time I'd heard a quantitative comparison like this (as opposed to "80% will give you longer battery life" without letting you know if it's just 5% more life, in which case I'd never use it). I did some more research on the subject, and found that other than deep discharge or very rapid charging, one of the worst things you can do to a lithium battery is to fully charge it, and then leave it fully charged at high temperature. Evidently, crystal structures will form that inhibit the normal chemical reactions from taking place in some spots on the battery, thereby reducing its ability to charge and discharge in those areas.
2) I had been 100% charging every other day to prevent "memory" effects from occurring, which are a problem with NiCd batteries. The engineer told me this is unnecessary; this type of battery does not develop memory if you just use it around the middle of its range. In fact, that is desirable.
3) I told him how I was going to have a L1 and L2 charger, and only use L2 when I absolutely needed it, since I wanted to be "gentle" and keep the battery cool when recharging to minimize stress. The engineer told me that although L3 charging will definitely heat things up and reduce battery life, L2 is not much different than L1, since in both cases you're charging the pack up over many hours. I had requested a feature where you could limit charging current to reduce the thermal load on the battery pack - they told me this was not worthwhile, at least at the 3.3kW level that L2 has available now.

As a result of the conversations, I changed to plugging in every night, using the timer set to 80% max, and stopped worrying about what L2 charging will do to long-term battery life. I have encouraged Nissan to publish more quantitative details of their life testing, but until then, I hope this helps answer some of the questions on this thread.

- Bob

Herm
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 4:35 pm

I am very surprised a Nissan engineer admitted that, it could turn into a marketing disaster.

From a recent thread that talked about the cell voltage when fully charged to 100% we found out that when Nissan says 100% they mean it. Still it could be easily verified by ANY owner that owns a DVM and knows what they are doing... please post your results so we can move on.

I do believe that Nissan reserves about 3kwh on the low side of the battery, and you can never access it, not even in turtle mode.

The question is, will people that routinely charge to 100% reach 100k miles of battery life?.. or perhaps 150k?

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planet4ever
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 7:12 pm

rwherrick wrote:1) One of the Nissan Engineers that I met questioned why I wasn't using the 80% charge feature, given that I have a short commute. He claimed that Nissan's testing shows that only charging to 80% will double the battery pack life on average, when compared to fully charging the battery pack.

I probably don't know what I'm talking about, however it was my impression from more knowledgeable posters on other threads that lithium cells can be charged to 4.2v, but the LEAF never lets you charge beyond 4.1v, because it switches to constant voltage charging at that point. I wonder if we might not have a semantic confusion here. Perhaps by "fully charging" the Nissan engineer meant 4.2v, while the LEAF literature means "all you can stuff in at 4.1v" when it refers to 100% charging.

I am prepared to believe that 100% charging can shorten battery life somewhat, but cutting it in half is way beyond what I am ready to accept.

Ray
End of April 2013: Traded my 2011 SL for a 2013 S with charge pkg.

Herm
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Re: Battery degradation info, 80% vs. 100% daily charge

Sat Jul 16, 2011 11:16 pm

most likely 4.15v, which is for most purposes is 100% charge. Someone reading this right now may be the first one to actually measure the voltage and forevermore settle the question!.

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