JJnHAWAII
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 4:45 pm

It sounds like the jury is still out on waiting to charge after use. The battery should at least in theory last longer with a rest period before charging. Does it really matter that much though? I'm only using L1 and charge immediately upon returning home.

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surfingslovak
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 5:26 pm

JJnHAWAII wrote:It sounds like the jury is still out on waiting to charge after use.
Yes, I think your assessment is correct. We don't even have consensus on questions that should be more straightforward than this, such as charging to 80%. If you asked me, I would go with the conservative recommendation and say that it won't hurt to let the battery rest a bit before charging. I don't follow that approach personally though, and I'm not convinced that it would have any measurable benefit. In my experience, there is almost no discernible difference in pack temperature in day-to-day use.

Stoaty
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 5:42 pm

surfingslovak wrote:We don't even have consensus on questions that should be more straightforward than this, such as charging to 80%. If you asked me, I would go with the conservative recommendation and say that it won't hurt to let the battery rest a bit before charging. I don't follow that approach personally though, and I'm not convinced that it would have any measurable benefit. In my experience, there is almost no discernible difference in pack temperature in day-to-day use.
As far as I can tell, the effects of ambient temperature on battery pack temperature are far greater than the effects of charging, at least when going to environments of 90 degrees F. or more with the Leaf parked in the sun.
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surfingslovak
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 7:26 pm

Stoaty wrote:As far as I can tell, the effects of ambient temperature on battery pack temperature are far greater than the effects of charging, at least when going to environments of 90 degrees F. or more with the Leaf parked in the sun.
Yes, that seems to be a reasonable assumption. However, Nissan has gone on record saying that their batteries don't require a TMS. Well, at least not in the US market, and that they were considering active cooling for markets such as Dubai.

While it's reasonable to assume that it's safe to charge the Leaf to 100% each and every day and park it in an unshaded spot in a hot parking lot, Nissan does not tell us what a more careful approach would yield in relative terms. If an average pack degraded 20% after five years of careless use, and 15% after 60 months of babying, then perhaps the extra effort was not worth it. Obviously, it should be up to the owner to decide. And what if the difference was more significant? Unfortunately, Nissan is probably not going to tell us, and will continue to hide behind references to proprietary battery technology.

About the report we discussed earlier, I wanted to add that although the cells under test had the same basic chemistry, they were not optimized for EV use. I found a spec sheet for LG Chem's E1 cell. It's from 2004 and it's very likely that the cells they are using in the Volt have evolved quite a bit since then. Likewise, I imagine that the AESC cells the Leaf is using are similar in their characteristics. And again, we are only doing this comparison, because AESC does not tell us anything about cycle and calendar life of their cells.

The E1 cells have about ten times better cycle life than the ones we looked at earlier. They were cycled in a wider range too: 3.0 to 4.2V versus 3.4 to 4.2V. The capacity loss was about 15% after 500 cycles versus 15% after 60 cycles. Although LG Chem does not say anything about calendar life, it's likely that they optimized that characteristic too and E1 performed much better than the cells examined by the University of Michigan in their report.

I'm only saying this to underscore that anything we do, from charge protocols to storage temperature has only a relative effect on battery life and the pack has already been optimized for EV applications with everything that it entails.

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Last edited by surfingslovak on Fri Sep 30, 2011 7:56 pm, edited 3 times in total.

Stoaty
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 7:38 pm

surfingslovak wrote:Yes, that seems to be a reasonable assumption. However, Nissan has gone on record saying that their batteries don't require a TMS. Well, at least not in the US market, and that they were considering active cooling for markets such as Dubai.

While it's reasonable to assume that it's safe to charge the Leaf to 100% each and every day and park it in unshaded spot in a hot parking lot, Nissan does not tell us what a more careful approach would yield in relative terms. If an average pack degraded 20% after five years of careless use, and 15% after 60 months of babying, then perhaps the extra effort was probably not worth it. Obviously, it should be up to the owner to decide.
It might very well be worth it if the 4% a year vs. 3% a year was carried out to 10 years, though: 40% degradation vs. 30% degradation might very well be the difference between the car still being useful for a particular person or not.
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surfingslovak
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 7:51 pm

Stoaty wrote:It might very well be worth it if the 4% a year vs. 3% a year was carried out to 10 years, though: 40% degradation vs. 30% degradation might very well be the difference between the car still being useful for a particular person or not.
Yes, of course, and the relative difference could be more significant too. Unfortunately, there are too many unknowns and Nissan does not make this easy, since they don't offer any battery capacity warranty. But even if they did, there could be owners interested in extending the useful life of their vehicles. I think those wanting to beat the metrics Nissan has used for their battery warranty, deserve answers and AESC is best qualified to provide them.
Last edited by surfingslovak on Fri Sep 30, 2011 11:12 pm, edited 1 time in total.

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ElectricVehicle
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 11:04 pm

surfingslovak wrote:
Stoaty wrote:It might very well be worth it if the 4% a year vs. 3% a year was carried out to 10 years, though: 40% degradation vs. 30% degradation might very well be the difference between the car still being useful for a particular person or not.
Yes, of course, and the relative difference could be more significant too. Unfortunately, there are too many unknowns and Nissan does not make this make this easy, since they don't offer any battery capacity warranty. But even if they did, there could be owners interested in extending the useful life of their vehicles. I think those wanting to beat the metrics Nissan has used for their battery warranty, deserve answers and AESC is best qualified to provide them.
The SOC meters might help us to see some capacity effects in 2 to 3 years, but then we'll have to make assumptions about what that owner did that affected the capacity, assuming someone treats the batteries the consistently for 2 or 3 years!

We'll certainly want to hear from the first people that have the first one or two dots disappearing from the far right section (Capacity Level Gauge, Owner's Manual 2-10) of the battery gage which indicates the pack capacity relative to new. It looks like the Avalable Charge Gauge goes from 0-12 bars based on the battery's current capacity. So if the battery after many years degraded to 80 % of new capacity, and is fully charged, the Available Charge (pg 2-9) would show 12 bars, while the Capacity Level would show 10 instead of 12 rectangular dots.
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 11:26 pm

ElectricVehicle wrote:We'll certainly want to hear from the first people that have the first one or two dots disappearing from the far right section (Capacity Level Gauge, Owner's Manual 2-10) of the battery gage which indicates the pack capacity relative to new. It looks like the Avalable Charge Gauge goes from 0-12 bars based on the battery's current capacity. So if the battery after many years degraded to 80 % of new capacity, and is fully charged, the Available Charge (pg 2-9) would show 12 bars, while the Capacity Level would show 10 instead of 12 rectangular dots.
Right, that's a very good point. The two people I'm always keen to hear from are Jimmydreams and gudy. There is also a highly interesting and appropriately named thread: I want my 281. I have reviewed the relevant section of the owner's manual earlier today, and while Nissan is quite specific about what to do (practice moderation and avoid heat), they don't quantify the impact battery care can have on battery life. If our understanding of the capacity gauge is correct, then the first bar won't disappear until the pack has lost about 16% of its original capacity. This might not be practical for our needs, we would want to detect battery degradation earlier so that we can make adjustments and avoid some of the pitfalls.

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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 11:39 pm

surfingslovak wrote:Right, that's a very good point. The two people I'm always keen to hear from are Jimmydreams and gudy. There is also a highly interesting and appropriately named thread: I want my 281. I have reviewed the relevant section of the owner's manual earlier today, and while Nissan is quite specific about what to do (practice moderation and avoid heat), they don't quantify the impact battery care can have on battery life. If our understanding of the capacity gauge is correct, then the first bar won't disappear until the pack has lost about 16% of its original capacity. This might not be practical for our needs, we would want to detect battery degradation earlier so that we can make adjustments and avoid some of the pitfalls.
Of course the various communtiy SOC meters for the LEAF will give us earlier insight and a more reliable base line than the gauge. I meant to mention in my earlier post that I know one person who uses LEAFs in his security patrol business just for the economics of saving gas money, and I expect some clients prefer his firm for the fleet of EVs and Prius he uses, way cool..! Back on topic, he's got 12,000 miles on one of his LEAFs already and he didn't mention any degradation yet. The warranty is 8 years / 100,000 miles, so he's already 12% into the warranty life. I think he's at a rate of 20,000+ miles / year.

I also started this thread Quick Charge to 60% - Better Battery Life? to discuss how we can get the most use out of Quick Charging (QC) with minimal impact to battery life to extend the tripops and utility of our LEAFs. While the Quick Charge itself may be expensive - $10? $20? since has high peak power and will likely be used on peak electricity, the far greater cost to me is any singnificant battery degradation it may cause, especially when you need 2 Quick Charges, or more, in one day to make a 150+ ile round trip.
Last edited by ElectricVehicle on Fri Sep 30, 2011 11:46 pm, edited 1 time in total.
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Re: Prolonging battery life, temperature, state-of-charge

Fri Sep 30, 2011 11:44 pm

ElectricVehicle wrote:Back on topic, he's got 12,000 miles on one of his LEAFs already and he didn't mention any degradation yet. The warranty is 8 years / 100,000 miles, so he's already 12% into the warranty life. I think he's at a rate of 20,000+ miles / year.
Great, yes, it would be very interesting to get some data from his fleet vehicles. If he didn't have an SOC meter, perhaps a loaner could be found. Way to promote his business BTW, very clever. I believe that Jimmydreams was well over 10K miles as well. He is in SoCal though.
Last edited by surfingslovak on Fri Sep 30, 2011 11:48 pm, edited 1 time in total.

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