Battery life - Charge to 80% or 100%

Back when I got my 2013 Leaf people were saying (I think) that charging to 80% would help lengthen battery life.

Lately I have seen threads where, from what I can infer, it seems that only charging to 80% can do the opposite.

So here is the question: Should I continue to run it to 80% or should I set it to 100%?

Basically what is the best way to extend battery life?

What is your location? Back before we knew about the battery capacity degradation caused by the high temperatures the car is exposed to, people made a big deal out of the 80% vs 100%. But, now we know your location has MUCH more to do with degradation than charging to 100%. I charge to 80% 5 days a week, but 100% on weekends, when I need it. I think this is great, because that gives the battery 2 days a week to go completely through an equalization cycle. From some posts recently, it appears to me that only charging to 80% may allow the pack to get more out of balance than often charging to 100%, which then limits your capacity to the weakest link, the lowest cell. My battery, although down to 77% capacity now, always shows no more than 12-17 mv difference between cells, very well balanced.

As a MY 13 S owner, I reviewed the data, and decided to charge to 100% daily, but to do it at 4-6AM using the built in timer, to simply reduce the number of hours spent at 100%.

I am in a medium climate (Philly), but have a very cool and shaded garage that runs from 50°F in the winter to 70°F in the summer. This coolness factored into my decision, as well as the fact that I am a 3 year lease....so if it does degrade a bit, I still get to give it back.

The timer approach does not significantly reduce usability (since I am at full range daily), but cuts down 100% SOC hours by >60% relative to not using the timer (charging starts at 4PM). If the battery does heat up during its daily outing in the summer, it also gets some time (12 hours) at 70°F to cool before it gets charged.

Is there evidence that long term 80% charging permanently limits capacity (due to lack of balancing)? My 2012 (12bar car, 16k miles since Jan2012 here in NH) is almost exclusively charged to 80% - end only timer during the week, immediate charge on weekends.

of course, I almost never drive more than 50 miles in a day, so I'm not really pushing this car very hard....

can't really give you a definitive answer but with more details from you, we can give you things to think about.

there is some data that suggests a better balance of the pack when LEAF is fully charged. keep in mind; fully charged does not mean 100% so its not as detrimental to charge your LEAF to its stopping point like your cell phone for example.

What you need to decide is can you live with less range? (not using that extra SOC?) If you are within 25% of your range in your normal commute, I would charge to full every day unless you have a lot of public charging options and don't mind stopping.

other than that; there is probably a very small benefit to keeping your SOC in the middle ranges but that comes with a strong possibility of a HUGE inconvenience if you need that range to get something done.

For some, its easy. They are organized, etc. for others, not so much.

I maxed it at 80% during the summer months but now that it is cooling off some I have started going to 100% with the timer set to finish just before I leave.

My take is that charging to 80% is better, as long as you also charge it to 100% and let it EQ and shut off regularly. This seems like sort of a false dilemma to me. Do both!

I agree, which is why I think my charging pattern is optimal. As I learned from my battery backup solar system, periodic equalization is a NECESSITY whenever you have this many cells in series. Although my solar is lead acid, and the Leaf is lithium, I'm sure the principal still applies.

keydiver said:

I agree, which is why I think my charging pattern is optimal. As I learned from my battery backup solar system, periodic equalization is a NECESSITY whenever you have this many cells in series. Although my solar is lead acid, and the Leaf is lithium, I'm sure the principal still applies.

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I have basically (except for very few exceptions) charged to 100%. I just broke 13,000 (17 months) and haven't lost a bar. I'm located in Milwaukee, which can have hot summers and cold winters, mostly cold....man I hate cold....

While I don't know how many GIDs I'm putting out, I can put it this way. My total commute is 55+ miles and about 95+% of it is freeway. Without heat or air running, I'm still averaging over 90 miles per charge (top speed of 60).

It should be noted that the Leaf's BMS appears to be set up like any other, to equalize at 100% and only then. If you never charge to 100%, the car never gets an EQ on the pack.

LeftieBiker said:

I should be noted that the Leaf's BMS appears to be set up like any other, to equalize at 100% and only then. If you never charge to 100%, the car never gets an EQ on the pack.

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That seems to be true in my experience. I had a long stretch (months) where I strictly charged to 80% with end-time timer. Then I made an extended drive. Once the battery got down to 1 bar, the GOM started losing range much faster than normal. I attributed this to cell imbalance.

And so for the next few days I charged to 100% also giving the car several hours of time on the plug after charge completion. One sign of a rebalancing is getting a second "charge complete" notice from carwings, and that happened on both subsequent charges. So it seemed to take at least 2 of these "rebalance" charges to get the cells equalized after months of 80% charging. A subsequent long-range drive showed the effect: The last bar was the "fat" bar once again.

I didn't have any OBD device at the time; just empirical observations.

essaunders said:

Is there evidence that long term 80% charging permanently limits capacity (due to lack of balancing)?

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As long as you're not discharging to a particularly low SoC, there should be no permanent harm in not balancing the pack. The reason I'd be concerned about low SoC is that in an unbalanced pack some cells will necessarily be lower than others. You don't want to be further stressing those low cells.

Thanks everyone for the feedback. (for some reason I was not getting any notices that anyone had replied. I just checked to wonder why and saw all these replies).

To answer an earlier question, I live in Atlanta. Car is 11 months old with 11K miles on it.

I have been charging to 80% because my normal routine was to plug in around 4:30PM and unplug about 14 hrs. later. This would have left the car charging with the battery at 100% for about 10 hours, and I wanted to avoid that.

I just changed to 100% and have not lost any bars yet. What I have noticed is that in the morning the battery would show 80% exactly, but lately it was going up a little higher when I started up (82-84%), but those first few percentage points dropped very quickly. Cells not equalized??

I am running at 100% for now. After reading these posts may switch back to 80% for the summer months to avoid heat stress.

For a test, I will try switching back to 80% after a couple of 100% cycles to see if it still climbs above 80% after 15 hours or so of charging. Would be interesting to see if equalizing changes it back to hitting 80% and stopping.

When Summer comes I agree about changing back to 80%, but as long as you pick a cool day and a cool pack, do an occasional 100% charge even then, to keep the pack balanced.

LeftieBiker said:

It should be noted that the Leaf's BMS appears to be set up like any other, to equalize at 100% and only then. If you never charge to 100%, the car never gets an EQ on the pack.

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This is not true. Leaf Spy or LeafDD or any other CAN device will confirm this.

The pack will get balanced at any time it deems necessary, even if you never charge over 80%.

All a 100% charge does is make any cell imbalance stand out more, so it will balance the pack a bit better when charged to 100% other than 80%.

I don't quite understand the obsession with cell balancing - nothing is harmed by the pack being a bit out of balance, though you may lose a couple miles of range when you do charge to 100% and drain it down below VLBW. If you really need every last mile and don't charge to 100% often, you'll need a bit of time and a number of 100% charges to get the pack well balanced. You'll see that after the first 100% charge it will shunt a lot of cells and will do so for at least a couple days (even if only charging to 80%), just with fewer shunts on subsequent days.

This is not true. Leaf Spy or LeafDD or any other CAN device will confirm this.

The pack will get balanced at any time it deems necessary, even if you never charge over 80%.

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What exactly occurs in sub-100% balancing?

ok, after 6 days of charging to less than full by

going 3 days without plugging in at all.
also have stints where I plugged in for just a few hours here and there never getting to 11 bars
so I did full charge last night

my ahr went from 66.39 to 63.57

kwh available from 22 to 21.4

GIDs from 284 to 276

so what does this mean? probably not a whole lot. if you can live with the reduced range of 80% charging then do it but if your day to day driving at 80% charging is bringing you down to 2-3 bars you probably should be charging to full anyway BUT

things to consider and I have no proof of anything I am about to say or how bad or good any action is its just general battery stuff.

** Minimize time spent at full charge. 12 hours is probably fine but the less the better.

**worse in my opinion is very low SOCs. If you have to, plug in for an hour or two when you first get home. This gets the pack off those > 20% SOC and plus gives u some range in case something unexpected comes up. Keep in mind; any cell that is out of balance, its delta is greatest at low SOC. This can cause IRREVERSIBLE damage

**ANY charge going in or out of the battery is "grains of sand" from your hourglass and its one way. IOW, the charge your battery takes or receives is absolute. putting charge back does not extend your battery's overall cycle count.

a LOT of people dispute my practice of steady speed driving using neutral to do so thinking its better to mitigate pedal pressure to "dead band" (centering the power meter) the LEAF. I do not believe this.

I feel that coasting is exactly that. putting miles on an EV with little or no impact to the cycle count of the battery.

now, we all have different driving conditions and neutral driving is far from easy and it does leave you vulnerable to a greater sin; using friction brakes instead of regen to slow down.

DaveinOlyWA said:

...if you can live with the reduced range of 80% charging then do it but if your day to day driving at 80% charging is bringing you down to 2-3 bars you probably should be charging to full anyway...

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While I don't have an issue with most of what you said, I disagree with this. 2-3 bars is in the 30% SOC range. That is a near ideal place to end the day's driving. If you look at the cell-pair voltages they will be way, way above anything that will remotely be deleterious to the battery. If I get home at 20% SOC I just leave the car until my next timer charge (midday for me, to use my solar power directly). The cell-pair voltages are well within the safe zone. No need to charge right away unless I need the car for another trip. It also helps keep the battery cooler.

The question keeps popping up, over and over and over!

http://daveinolywa.blogspot.com/2014/10/80-charging-why-i-dont-miss-it-and-why.html" onclick="window.open(this.href);return false;

dgpcolorado said:

DaveinOlyWA said:

...if you can live with the reduced range of 80% charging then do it but if your day to day driving at 80% charging is bringing you down to 2-3 bars you probably should be charging to full anyway...

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While I don't have an issue with most of what you said, I disagree with this. 2-3 bars is in the 30% SOC range. That is a near ideal place to end the day's driving. If you look at the cell-pair voltages they will be way, way above anything that will remotely be deleterious to the battery. If I get home at 20% SOC I just leave the car until my next timer charge (midday for me, to use my solar power directly). The cell-pair voltages are well within the safe zone. No need to charge right away unless I need the car for another trip. It also helps keep the battery cooler.

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you are right. I probably should have said LBW or something but not sure I can agree with 30% SOC being ideal. its probably good but my idea of ideal is likely to be 50% SOC. whether I am right or you are right probably does not mean a whole lot either way cause the difference is likely insignificant