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80,90,or100% ?

15K views 84 replies 35 participants last post by  Entropy512  
#1 ·
New to EV with my 2023 Bolt.
factory setting is to charge to 100%
My electrician told me to change setting to either 80 or 90 % unless I’m taking an extended trip
What is recommended?
 
#8 ·
You want to stay out of the upper and lower 10-15% of the pack for routine charging, which keeps you in the area of the charge curve that puts the least stress on the cells. There's some permanently unused headroom in the pack, so charging to 90% is fine.

I'm one of those folks who charges to 100% every fourth or fifth time to let the BMS balance and recalibrate. Don't overthink this, you could charge to 100% every single time and the only real ramification is perhaps the battery capacity will degrade an extra percent or two every 100,000 miles.

I also like to let the car stay plugged into the charger for at least 4 hours after the traction battery is charged so it'll have a chance to charge the 12V battery too. Lead acid batteries take a long time to charge from 80% to 100% and their life suffers significantly if they're discharged more than 50% and/or not given a full recharge every week or so. For that reason, I always charge the car at least on a weekly basis. The car itself will keep the 12V battery from dropping too far but won't give it a full charge as frequently as I'd like unless it's plugged in.
 
#9 ·
You want to stay out of the upper and lower 10-15% of the pack for routine charging, which keeps you in the area of the charge curve that puts the least stress on the cells. There's some permanently unused headroom in the pack, so charging to 90% is fine.

I'm one of those folks who charges to 100% every fourth or fifth time to let the BMS balance and recalibrate. Don't overthink this, you could charge to 100% every single time and the only real ramification is perhaps the battery capacity will degrade an extra percent or two every 100,000 miles.

I also like to let the car stay plugged into the charger for at least 4 hours after the traction battery is charged so it'll have a chance to charge the 12V battery too. Lead acid batteries take a long time to charge from 80% to 100% and their life suffers significantly if they're discharged more than 50% and/or not given a full recharge every week or so. For that reason, I always charge the car at least on a weekly basis. The car itself will keep the 12V battery from dropping too far but won't give it a full charge as frequently as I'd like unless it's plugged in.
Thank you for your input👍
 
#71 ·

Nope, not actually an exception here.

BU-808: How to Prolong Lithium-based Batteries is a pretty good read in general on preserving your battery. In general, 90% is a massive improvement over 100%, 80% is a significant improvement over 90, 70% is another noticeable improvement, but past 70 or so, the improvement is less likely to be worth the tradeoffs. (See Tables 3 and 4. Keep in mind the Bolt has a somewhat different chemistry than listed there, so cell voltages don't directly translate, but general percentages still roughly apply)

Before someone says "well some GM engineer said 100% was OK" - remember the context. He's an engineer only being allowed to say what management (including marketing) approves. In this case, the context is, what is a failure? For GM, that's a warranty claim. That happens if you lose more than 30% of capacity after 100k miles or 8 years. (May have exact mileage/years a bit off). If that's perfectly OK with you, charge to 100%. If you want your battery to be likely in better shape than "bare minimum for no warranty claim", take better care of it.

Also remember that a few years later, when the s**t hit the fan with the recall, what did GM do as part of an interim fix? Outright block anything above 80%.

I charge to 70 in summer and 75 in winter - gives me plenty of spare range to work with unless I'm expecting to go long-distance. Also lets me get some "extra" juice if I hit a free public charger (that can hit 80... **** you recall). Also as others have mentioned, charging to 100% loses regen for your first few miles.
 
#11 ·
I am always the contrarian on this... and this site has many long threads on this topic with oodles of charts and lots and lots of facts theories.

I'll quote this line:

"Don't overthink this, you could charge to 100% every single time and the only real ramification is perhaps the battery capacity will degrade an extra percent or two every 100,000 miles."

Based on that statement I would argue that if you only charge to 80% then your battery is already degraded since you are not getting the performance you paid for.

But my opinion is only an opinion (and not a popular one). I bought the car for me, not the next person to drive it, and with the vagaries of the charging infrastructure I want my tank full.
 
#12 · (Edited)
I am always the contrarian on this... and this site has many long threads on this topic with oodles of charts and lots and lots of facts theories.

I'll quote this line:

"Don't overthink this, you could charge to 100% every single time and the only real ramification is perhaps the battery capacity will degrade an extra percent or two every 100,000 miles."

Based on that statement I would argue that if you only charge to 80% then your battery is already degraded since you are not getting the performance you paid for.
It's not "theory". Who is this quote from? Where does such data/claim come from?

You do realize that the battery warranty allows for up to 40% capacity loss within the 8 years/100K miles, whichever comes first, right?

If you don't need 100% every time, there's no reason to charge it to 100% each time. Sure, do it when you need it.

Notice slide 8 of https://www.nrel.gov/docs/fy16osti/66708.pdf suggests that a lower average SoC is better? Bolt uses an NMC-based battery. If you charge to 100% then say 1% to 20% each time, what do you think the average SoC will be vs. someone w/the same usage and charging to something lower like 80%?

I wouldn't go as far as VW (Charge to 100%? 80%?) where they don't want people parking their cars at above 80% or below 30% for more than 12 hours. They were also using LG Chem back then, like Bolt.

One roundtrip of my commute only uses about 10% of my battery on my former Bolt and current '22 Niro EV. If I charged to 100% each time at work, my average SoC is most of the time is going to be above 90%.

The times I need to actually charge my former Bolt or current Niro EV to 100% is only a few times/year.

Notice page https://www.chevrolet.com/bypass/pc...ALS/5000/MA5700/en_US/3.0/23_CHEV_Bolt_EV_OM_en_US_U_84953304C_2023MAR10_3P.pdf page 223 recommends long-term storage at 30%? This is inline w/known li-ion battery science. These aren't lead acid batteries which DO like being full.

We've been through this many times (e.g. What % Should I Charge To?) and it seems you also participated there.
 
#15 ·
What is recommended?
Here's a nice, easy to understand explanation of battery health from Recurrent.
EV Battery Health after 250 Million Electric Car Miles
These people monitor and study thousands of EV batteries.
Won't the traction battery keep the 12 volt charged, while the car is on, regardless of whether it is plugged in?
Well, you could leave the car on all the time and never have to worry about coming out to a dead 12V after a week of not driving. But it's easier for the car to maintain both batteries when it's plugged in. When the car is off and unplugged, it checks the 12V every four days. When it's plugged in , it checks it every six hours. Also, when it's plugged in, it will start charging the 12V sooner than when unplugged.

Imagine now that you make about a dozen 5-minute drives over a week's time and the car never runs long enough to fully recharge the 12V battery. It just gets lower and lower. Eventually it will get low enough that the car will charge it a little even when it's off and unplugged. But that chronic low voltage will take a toll on the 12V battery.
 
#17 ·
When I'm at HOME paying for power I have my settings at 80%. When I'm AWAY riding my bike at the park with free power I have my settings at 100%. I haven't had to pay for power away from home yet.
 
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#20 ·
The state of the batteries at 100% charge is well known, and this holds true for all rechargeable lithium based batteries (except lifepo4), 100% charged is the point of highest stress on these lithium cells. So charging to 100% every time does increase degradation, its not immense an extra 3-5% over 100k miles. It increases the possibility of failure, again not immensely but at 100% your chances are higher than those that only charge to 80-90 percent. Because of the battery recall the diagnostics and monitoring of the battery are much more aggressive than previous, so your chances of a fire are much lower as it seems to be doing a much better job at detecting the conditions that lead to a fire. There have been multiple posts here in this forum from members who have gotten the alert to not drive and get the battery serviced, aka, replaced.

Having said all of that, you should charge the way that fits your lifestyle and driving needs. If you need to be at 100% to get your normal drives in, charge to 100%. If you have shorter drives and don't need to be at full charge, set it lower and charge more often. Myself, I have hilltop on (I have a 2017 so I can't set a target percent) and I leave it that way unless I know I need to take a long drive. I do it more because I like to have regen 100% available from the start of my drives and I rarely do a trip that needs even half of the battery.

So while it is good to know all of that, as I said, the reality is you figure out what fits you and charge to fit that. Short of draining the battery below 15% often you really can't screw them up easily.
 
#22 ·
This is a hotly debated topic. Ideal is charge to 50%, store it in a climate control garage and don't drive it, the closest you can reasonably keep it in those conditions the longer your battery will last.

If charging is as simple as opening the charge door and extending your arm to your home charger and you can be 40-60%, what the heck, why not?

If you need 10-90% and only plan to keep the car for 5 years, why are you stressing?

How will all this impact your battery life you ask? Unknown, there are no modern packs that are at end of life. It seems the 10-90% people may just in fact have their battery packs last longer than the car, but again, it's unknown.

So, people want an answer. They want a thing they can just plan around and go. That's not how BEVs work, at least not yet. Not enough data.
 
#31 ·
I am among those who just plugs the car in whenever at home. It's just a habit I developed that reduces the risk of me forgetting to plug in and consequently being unable to use the car. Also, unless the car is kept in a heated garage, I believe the manual says to keep it pluggedin colder weather.

I don't know if the positive effect on the battery longevity, achieved by limiting the charge to 80-90%, is pronounced enough to bother. The battery already has some headroom to provide the necessary safety margin.

Also, for some drivers there is such a thing an unplanned trip. In my case my usual 100-something miles daily routine can turn into 180 miles in a heartbeat, and I really, really want to minimize the risk of the car battery' SoC dictating what I may or may not accomplish.
 
#42 · (Edited)
3.0 kWh. At the time (2015-16), to my knowledge it was 3X larger than any battery system in any clinical device on the market, all of which were used to provide standby backup power. In contrast, this system was designed to undergo three full charge/discharge cycles per workday (two day shifts plus an overnight run) over a four year service life with less than 20% battery capacity degradation in that time. It was a fun project and it turned out well, at least until the private equity folks got involved.

EDIT: regarding accelerating and DCFC, I don't sweat either. Most lithium batteries can handle extended 1C discharge and recharge rates without any issue at standard temps. With a pack capacity of 66kWh, you'd be hard pressed to stress the pack with hard driving and the Bolt's 55kW DCFC charger will never achieve even 1C. Even if it's extremely cold out, both power draw and DCFC can be throttled down by the car to keep things in a safe range.
 
#44 ·
This thread reminds me of OIL threads on all the ICE forums :ROFLMAO:
I live off grid and charge to 90% and add in battery balancing charges to 100%
for planned longer trips. I leave the car plugged in 100% when not in use.

I have not started 12 volt battery monitoring as of yet. That will happen soon!
My 2017 was used the same way, but, always charged to 100% and I found it
necessary to use my battery charger to maintain my 12 volt battery to "my"
desired level of conditioning. Again, YMMV!

My 12 volt battery never had an issue in my 2017.
I plan on the same service life and beyond for the 2023!
The OEM, AGM should last at least 7 years with proper service, IMO!
 
#65 ·
New to EV with my 2023 Bolt.
factory setting is to charge to 100%
My electrician told me to change setting to either 80 or 90 % unless I’m taking an extended trip
What is recommended?
I live at the top of a mountain (well, 4,000ft) and rarely drive more than 100 miles round trip so I usually leave it set to 80% - It's closer to 90% by the time I get to the bottom of the hill anyway ! The flip side of this equation is that I need 50 miles of range to drive the last 15 miles home.

However, if I am going anywhere further, I do change it to charge up to 100% - That is usually enough to get me to a place I want to stop for food even if I haven't arrived at the destination, so charging at a DC station is faster than filling up with gas (I'm eating while it's charging).

I do love never needing to stop at a gas station normally.
 
#66 ·
New to EV with my 2023 Bolt.
factory setting is to charge to 100%
My electrician told me to change setting to either 80 or 90 % unless I’m taking an extended trip
What is recommended?
Basically, as a battery charges it's resistance to excepting that charge goes up. That shows up in a few ways. 1st, heat. Battery becomes a shunt in many ways. Like the old incandescent light bulbs (pure resistance in those filaments) that produce light buy offering just the right amount of resistance to glow brite, but hot.
2nd, as the resistance goes up so does the time to charge. That last 20% seems to take forever, if you know what mean. And produces a lot a heat as in 1st above.
If you're just driving around the county like 99% of us, do you need to charge that last 20%? Up to you of of course.
 
#72 ·
It's important to keep in mind that most non-EV uses for lithium batteries call for charging on a daily or near-daily basis. In that case, charge cycle count is pretty important and it's the metric that most all these studies are aimed at maximizing. If charging to 100% gives you a useful life of 1000 charging cycles but charging to 80% yields 3000 charging cycles, you're talking a useful battery life of only 3 years versus 9 years in a daily charging scenario.

EV's are different. A Bolt will give you ~250 miles on a full charge, which equates to only 400 charge cycles for 100,000 miles. By extension, it only takes 1000 charge cycles to get 250,000 miles. In other words, you might in theory sacrifice a lot of charge cycles by charging your EV to 100% every time but in practice, cycle life is likely not going to limit the life of the vehicle.

This is why I say "don't overthink it". If you want to charge to 100% every time, go for it. You may sacrifice a bit more pack range late in the life of the vehicle but your GOM will likely be more accurate and if it gives you peace of mind to have a "fuller tank" or if you sometimes need to take a longer unexpected trip or you just want to plug in less often, it's a rational tradeoff.

If you want to baby your battery to get the longest cycle life or fear that the Bolt's batteries aren't as robust as they should be and want to limit the chance of them failing catastrophically, or you don't really know what the truth is but figure it can't hurt to follow conservative guidance, that's fine too.

I shoot for the middle ground because my use case is short trips around the city with an ICE vehicle for planned or unplanned longer trips. I charge to 90% routinely and to 100% every fourth or fifth charge to let the BMS top-balance the pack (which helps range) and recalibrate the GOM. If that drops my car's theoretical life from 600,000 miles to just 500,000 miles, I can live with that.
 
#79 ·
So, I'm going to guess that the automakers, not wanting millions of warranty replacements, built some room into the charging cycle that when you hit the maximum level of charge you can get, there is still more room at the top. You reach 100 percent of what you can charge, but they is probably another 5 percent left.

Sure, I'll normally charge to only 80 or 90 percent....
 
#80 ·
So, I'm going to guess that the automakers, not wanting millions of warranty replacements, built some room into the charging cycle that when you hit the maximum level of charge you can get, there is still more room at the top. You reach 100 percent of what you can charge, but they is probably another 5 percent left.
That varies. Some provide very little. And then there's Toyota who give a very big buffer.
 
#82 ·
Battery degradation is really a thing. My 2015 Spark EV (different battery from the 2014) was down to 14.5 kWh when I sold it. Plenty of range for things like grocery shopping and around town and not enough to qualify for warranty replacement, but definitely degraded and only at 8 years and 29K miles.

The Spark EV did not have the ability to limit charging at less than 100%, and for me the ability to limit charging at a level less than 100% is huge, not only for battery longevity, but to get full regen, since I live uphill from town about 1000 feet up. I don't have the numbers in front of me, but going off memory I think that I'm actually getting better efficiency in the EUV than in the Spark. I'm sure that's because of the regen factor.

The day before yesterday I ran into a 2017 Bolt EV owner from the next county over in the parking lot at Walmart. He flagged me down and we had a chat. His Bolt had 112K miles, he really liked it, and he said that he planned to drive it until the wheels fell off. I didn't bring the subject up, but it sounded like he didn't have any noticeable degradation. I asked him whether he used hilltop reserve, and he said that he did.

For me, I currently have the charge limit set to 75%. Charging stops a little short of that, but the GOM still shows well over 200 miles, and generally about 20 miles is the most I drive in a day. At this charge limit if I decide to take a long trip the next day I can bump the charge level up and still get to a full charge overnight at Level 1. I'll probably go up to 80% when the weather cools off and I no longer see the 200 miles. I just like seeing the 200.
 
#84 ·
Battery degradation is really a thing. My 2015 Spark EV (different battery from the 2014) was down to 14.5 kWh when I sold it. ...
I owned a '14 Spark EV for ~7 yrs and sold it recently with 98k miles. I don't have the exact spec but it had much less degradation than yours.
I would still see 71 miles on the GOM during nice weather. And that's with 80% interstate travel, and not in the slow lane.
I bumped the 92mph limiter about once a week commuting with my bros in the left lane! (y)
I know, that's not how you measure kWh capacity. The Spark EV gave you the numbers on the display to calculate kWh's. I kept a spread sheet of degradation, just too lazy to look now...

The '14 Spark EV's had the same LFP cells that the Fisker had back then. When they went teats up they took A123 with them and GM had to scramble to put the Volt cells in the '15+ Spark EV's.
I honestly don't remember having limited regen at the start of my commute,,, but then I live on a pancake...:cool:
 
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#83 ·
New to EV with my 2023 Bolt.
factory setting is to charge to 100%
My electrician told me to change setting to either 80 or 90 % unless I’m taking an extended trip
What is recommended?
Why would your 'electrician' be giving advice on operating your EV?
Did your Bolt come with an Owner's Manual?
Wouldn't that be a better place to get Bolt advice?

As stated, you don't get full regen power if it starts out at 100%.
And that's why it used to be called 'Hill Top Reserve'. If you live at the top of a mountain you want a place for the regen power to go.