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I wonder how level 1 vs level 2 charging affects battery life and efficiency. Does the battery take differently to fast vs slow charge in the long run?
 

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To recreate the experiment, I ran the car around town for several days without charging at night (my normal SOP). I made 285.3 miles on 56.2kW (5.1m/kW and the average temp was in the 70’s). The range read 3 miles when I dared go no further. The JuiceBox says it took 59.993 kWh to stuff 56kW into her. To be able to still use ~56.5kW of the 60kW battery seems pretty good.....to me anyway. That’s 94.2%.
You've got your units wrong again. In all of the above cases, kWh are the correct units.

kW and kWh are very different metrics. Please see https://www.mynissanleaf.com/viewtopic.php?p=520169#p520169.
 

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I wonder how level 1 vs level 2 charging affects battery life and efficiency. Does the battery take differently to fast vs slow charge in the long run?
On a Nissan Leaf forum a few years ago someone quoted a battery expert who said L2 provided enough power to burn off something that builds up in the cells that L1 charging could not. Sorry, cannot remember the specific terms used.
 

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[....]
And some interesting surprises

Depth of Discharge (DoD) is critical and can cut battery cycle life by a factor of four if constantly repeated. A model battery may have a 20,000 cycle life discharging 40% regularly and only 5,000 cycles discharging >95%. This condition may be an issue with drivers who adopt a 'gasoline' fueling model: run to near empty then hit the DCFC. Remember, this is not going to happen with one long drive; 5,000 daily cycles is well over 15 years.

I enjoyed the read and hopefully you can add to the forum.
As you say, it is not going to happen over one long drive, but it does beg the question of getting a sense of how much damage is done over just a few discharges >95%. For one thing, that is one method that some here seem to follow in order to get a sense of their own test their own battery capacity.
 

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I'm more paranoid than most when it comes to battery degradation but even I think the occasional discharge to 0% (or thereabouts) or the occasional charge to 100% won't be noticeable.
I think most of the paranoia stems from the days when the LION in our cell phones would degrade down to nothing in 2 years or less.
The biggest cause of that issue was that phones had no BMS AND people would leave them ON overnight while charging. The phones would literally charge 100%, stop, drop to 99% then charge back up to 100% again.. over and over, hundreds, maybe thousands of times overnight.

I'm not saying we've completely solved LION degradation issues, but with BMS to prevent the situation described above, and to regulate charging in other aspects as well, in addition to temperature management systems, and better chemistry, we should be looking at long battery life.
 

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On a Nissan Leaf forum a few years ago someone quoted a battery expert who said L2 provided enough power to burn off something that builds up in the cells that L1 charging could not. Sorry, cannot remember the specific terms used.
It's always been assumed slow charging conventional 12V batteries was better than fast charging, for longer lifetimes.
 

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To recreate the experiment, I ran the car around town for several days without charging at night (my normal SOP). I made 285.3 miles on 56.2kW (5.1m/kW and the average temp was in the 70’s). The range read 3 miles when I dared go no further. The JuiceBox says it took 59.993 kWh to stuff 56kW into her. To be able to still use ~56.5kW of the 60kW battery seems pretty good.....to me anyway. That’s 94.2%.

Armed with the comments in this thread, the paper I still need to read and the data I’ve gathered, I’m willing to put this to bed......for now. I think I’ll try seeing how far down I can take her every quarter or so and see what the long term data tells me. Stay tuned.
If I remember correctly, you could still have something like 10 miles of range left after the GOM stops displaying, which would represent about 2 kWh in your case. You also don't have a SoC figure when you had consumed 56.2 kW, so we don't know how much was left. My guess is you have better than 94% capacity remaining.
 

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A friend of mine has a B-I-L who's an EE and works at the local battery plant (XALT). They've tested and dissassembled a Bolt battery pack. His summary - the pack will last forever.
Michigan? I think the Bolt will rust out before the battery pack goes.
 

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Hey, @p7wang, it's cool that you've stumbled upon “Battery University”. As a relative newcomer to the forum, you might be unaware that its articles have been referenced on various threads on the forum (no surprise, since the site has been around for a while and its articles are usually pretty unchanged from several years ago).

It's worth remembering that
  • The article you took a screenshot of (but didn't link to) dates back to 2010. It has been updated periodically, but the tables you quote are from 2016.
  • The article is mostly about laptop and cell-phone batteries.
  • The NMC 622 chemistry in the Bolt isn't specifically discussed on that page (nor have I found much about them on the site as a whole). NMC 622 can apparently support higher voltages than the usual 4.2 volt maximum of most Lithium Ion batteries, although manufacturers like LG will still state 4.2 volts as a maximum voltage as they care about battery longevity in automotive applications.
  • GM has said that the Bolt has a (small) buffer at the top and bottom end, so when a Bolt charges to “100%”, ODB-II data indicates it's really charging to 96%.
  • Most published papers are on base-line cells, not automotive-grade ones with proprietary additives, which really do make a performance difference in practice.
The most important question is the one we don't have a full answer for. How many cycles does a Bolt battery need to go through before it starts to decline significantly. Is it 500? (119,000 EPA miles), or 1000? (238,000 EPA miles), or more? What factors influence that number.

What we do know is that there are Bolts out there with @NewsCoulomb and @wrillo both have well over 100,000 miles, with fairly harsh usage patterns, and modest degradation.

Maybe when we get people putting 250,000 miles on their Bolts, we'll know. But maybe not.
 

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I'm more paranoid than most when it comes to battery degradation but even I think the occasional discharge to 0% (or thereabouts) or the occasional charge to 100% won't be noticeable.
Interesting.

My own gut feeling is that discharging all the way to zero is much more harmful than charging all the way to full.

Not sure it's a fully justifiable position, though. Perhaps it's just the general feeling that I don't want to run any car all the way down to the dregs, because I'll start to get anxious and wonder if I'm going to make it. I'd prefer to avoid that anxiety anyway, regardless of whether it's good for the battery or not.

As such, the lowest I've ever gone is three orange bars (with ODB-II saying 13.33% displayed and 17.59% raw SoC), and that was just once.
 

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My own gut feeling is that discharging all the way to zero is much more harmful than charging all the way to full.
Since all OEM EVs are top balanced, discharging to zero would destroy your lowest cell. But the BMS on all OEM EVs monitors all 96 cells, and cuts off discharge before any one cell reaches anything close to zero.

12-29-18-3.jpg
 

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[...]
How many cycles does a Bolt battery need to go through before it starts to decline significantly. Is it 500? (119,000 EPA miles), or 1000? (238,000 EPA miles), or more? What factors influence that number.
Do you know if it is standard practice to treat a single cycle, by definition, as going from 100% to zero%? You seem to be taking the EPA miles of 238 and then assuming that as defined as one full cycle. I ask because I don't know what the standard engineering tests might be, or if there is one more generally accepted way to approach the matter.

Also, assuming some degradation with current mainstream battery technologies, the vehicle will not go its full EPA range by the end of the tests.
 

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Do you know if it is standard practice to treat a single cycle, by definition, as going from 100% to zero%? You seem to be taking the EPA miles of 238 and then assuming that as defined as one full cycle. I ask because I don't know what the standard engineering tests might be, or if there is one more generally accepted way to approach the matter.

Also, assuming some degradation with current mainstream battery technologies, the vehicle will not go its full EPA range by the end of the tests.
Yes, in the literature going 100%–0%–100% is a cycle, as is going 90%–40%–90% twice, as is going from 80%–60%–80% five times. Often people use the term “equivalent cycles” to make it clear that it's not necessarily 100%–0%–100%.

In a Bolt though, when you go from 80% to 30%, you probably got some regen, so maybe it's not right to say that's half a cycle, maybe it's more. Meh…
 

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132291 miles. We charge every day to 100% (no hilltop reserve) on a juicebox 40. In my field, we'd say that everyone is "nuking" battery degradation - over complicating and overthinking something insignificant. The simple truth is that the right pedal, ambient temps, and the climate controls have much more of an effect on our range than battery degradation... even after 106,xxx miles in two years as an Uber, and another 24,xxx miles under our care.

I'd like to hear from people that have run the battery empty and what effect that has had on their battery. That is going to have a more significant effect than daily charging 40% of capacity.
 

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I'd like to hear from people that have run the battery empty and what effect that has had on their battery. That is going to have a more significant effect than daily charging 40% of capacity.
Bought our 12/16 build Bolt LT, in July of 2017. Did a range test from 100% to 2%, per the Chevy app, in May of 2018...~56 kWh usable. Installed Torque Pro June of 2018...57.7 kWh batt cap reading. Ran capacity check, from 100% to 1.6%, per Torque Pro, in December of 2018...~57 kWh usable, 58.4 kWh batt cap reading. Ran the Bolt down to 3.6%, per Torque Pro, getting to an EA charger after an EV event in Blacksburg, end of April 2019. May 9th saw our highest batt cap reading ever...60.0 kWh. Since November we have been at our lowest batt cap reading ever...54.9 kWh.

As near as I can tell there is no clear cause of rise or fall of battery capacity...calculated or actually usable. My suspicion is that the original manufacture, and formation charge, of each cell has more to do with battery capacity, and ultimate life, than anything we owners can do.
 

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Yes, in the literature going 100%–0%–100% is a cycle, as is going 90%–40%–90% twice, as is going from 80%–60%–80% five times. Often people use the term “equivalent cycles” to make it clear that it's not necessarily 100%–0%–100%.

In a Bolt though, when you go from 80% to 30%, you probably got some regen, so maybe it's not right to say that's half a cycle, maybe it's more. Meh…
It has been mentioned that using regenerative braking has about 30% better range compared to when all he braking is done by friction. So in terms of cycles that might be adding a 30% extra. The problem is that it's not adding that in terms of linear discharge, so it's not a simple-and-cut case.
 

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It has been mentioned that using regenerative braking has about 30% better range compared to when all he braking is done by friction. So in terms of cycles that might be adding a 30% extra. The problem is that it's not adding that in terms of linear discharge, so it's not a simple-and-cut case.
My empirical data puts regen in about that 30% ballpark (in other words, if you used 10 kWh on a trip, really you pulled 13 kWh out of the battery but also put 3 kWh back in).
 
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