Battery Depletion before Recharging

[michael]

I have experience with battery fade. It happens!

My Focus Electric faded about 22% over three years, 50,000+ miles
My close friend's RAV-4 EV (with Tesla power train and batteries) faded about 20% over three years 75,000+ miles.

In both cases, this was enough fade to make the cars marginal for their intended use. Thank goodness both were leased, now someone else's problem.

The fact that the RAVs battery faded less over more miles is not testament to Tesla durability...it's due largely to the fact that the RAV battery is nearly twice as large as the Focus battery (42 vs 23 kWh) so it went through fewer cycles even though over more miles.

 

[Anonymous]

I have experience with battery fade. It happens!

My Focus Electric faded about 22% over three years, 50,000+ miles
My close friend's RAV-4 EV (with Tesla power train and batteries) faded about 20% over three years 75,000+ miles.

Yes! Until they invent a battery that does not fade with time (doubtful), we do not know if the fade was primarily a factor of time vs. style of charging.

Until the Bolt EV has been out there 8 years and GM compares the battery packs from those who decided to not charge to 100% vs. those who did, we really won't know which and how much!

 

[Anonymous]

But always be charging, no. That's the worst practice for battery life.

And yes, to agree with GetOffYourGas, there is good reason to believe that lower is even better than mid. But whenever I have made that point I get pushback, so I refrain from making that assertion.

So you do NOT plug in your Volts every night?

...If I know I'm not going to use the car for a few days, I don't charge it until the night before I will need it.

This sounds like the exact reason Neil Cavuto, the former business editor on FOX News used to rant against the Chevy Volt time and time again because his wife was too stupid to remember when to plug in an electric car! I was shocked she took such abuse on national network television:

The first 1:48 of this video:

https://www.youtube.com/watch?v=JiUcNGAJMSw

 

[michael]

I have experience with battery fade. It happens!

My Focus Electric faded about 22% over three years, 50,000+ miles
My close friend's RAV-4 EV (with Tesla power train and batteries) faded about 20% over three years 75,000+ miles.

Yes! Until they invent a battery that does not fade with time (doubtful), we do not know if the fade was primarily a factor of time vs. style of charging.

Until the Bolt EV has been out there 8 years and GM compares the battery packs from those who decided to not charge to 100% vs. those who did, we really won't know which and how much!

Of course we will, and in fact we already do. This subject has been studied at length and reported in scientific journals.

If one Googles "lithium battery aging model" it will produce over 2 million results.

The cells in the Bolt are well characterized by their manufacturer. We don't have to wait around 8 years to find out that cells installed in a Bolt perform in the same manner of all the other cells that come off the assembly line.

Fade is influenced by time, style of charging, temperature, depth of discharge, and other factors.

But batteries that are charged fully fade faster than those that are not. If someone knows how to change this, it will be an important breakthrough. But for now, it is inescapable electrochemistry.

 

[JerryBob]

Thank you for all the suggestions. It seems to be about getting the most charging cycles out of the battery. Liquid cooled (sorry Egolf & Leaf) battery packs help. If the battery reads fully charged on the Bolt is it actually only 85% charged? My i3 has a 22kw battery but it is rated at 18.8kw of usable which is the Hilltopper 85%. Timing the charging to 85% indicated sounds kind of tricky. Looks like buying a pre-owned EV adds another concern not knowing how the previous owner maintained the battery.
https://cleantechnica.com/2016/05/31/battery-lifetime-long-can-electric-vehicle-batteries-last/

 

[IMAdolt]

As it's been said and studied at length many times (other factors aside) the end user has little control over lithium chemistries degradation and can really only effect a few things. Lithium chem degradation is most significant at the top and bottom ends of there SOC to varying degrees, the only way the end user can control this at all is with charging habits (rates of charge included) and to some degree use and storage during temperature extremes.

Maybe LG chems proprietary tech is more resistant to SOC degradation but I bet if it's at all belter its negligible, we can guess/assume the engineers built in a SOC buffer to not allow us to actually charge to 100% SOC but I don't think that info has been made public.

So if we can't assume or we know there's no built in buffer then not charging to 100% all the time will make a noticeable difference to capacity over time, whether 1, 5 or 10 or 20% over whatever time/usage span, weather or not its significant or insignificant is up to the user or person buying you used car.

If the OP is concerned about any sort of degradation telling them to always be charging, 100% as often as possible all the time is irresponsible or ignorant.

the owner manual also states an acceptable battery degradation within warranty is 40%, I personally hope after 10 years and 100,00 miles I'll have more then 80% capacity, but time will tell.

 

[Anonymous]

the owner manual also states an acceptable battery degradation within warranty is 40%, I personally hope after 10 years and 100,00 miles I'll have more then 80% capacity, but time will tell.

Could you point us to where this is stated in the Bolt EV owners manual?

 

[IMAdolt]

the owner manual also states an acceptable battery degradation within warranty is 40%, I personally hope after 10 years and 100,00 miles I'll have more then 80% capacity, but time will tell.

Could you point us to where this is stated in the Bolt EV owners manual?

All mauls may not be the same but the one I found is page 322

"Propulsion Battery Warranty
Policy (Bolt EV)
Like all batteries, the amount of
energy that the high voltage
“propulsion” battery can store will
decrease with time and miles
driven. Depending on use, the
battery may degrade as little as
10% to as much as 40% of capacity
over the warranty period. If there
are questions pertaining to battery
capacity, a dealer service technician
could determine if the vehicle is
within parameters."

Now to clarify you may not see 40% or even 10% but it's what the warranty covers I'd hope it's a warranty intended to not be utilized due to typical wear and tear and only for catastrophic failures but if Chevy engineers foresee a typical depletion of even half the warranty maximum then reducing your typical 20% wear to 10% due to responsible driving, charging and maintenance habits could be very important to some people and not worth worrying about for others.

 

[Anonymous]

Thanks for that reference.

I will note that there is no discussion here in the manual about how to charge to minimize battery degradation.

 

[michael]

While it's not the very cell used in a Bolt, it is interesting to look at the specification for a modern LG brand lithium battery

https://www.imrbatteries.com/content/lg_HG2.pdf

Note that after 500 charge/discharge cycles, the battery is rated to retain 70% of its initial capacity. Coincidentally, 500 full cycles of the Bolt battery correspond to about 100,000 miles.

Bolt battery degradation can be reduced by controlling the charge/discharge limits (1000 cycles between 75 and 25% will be easier on the battery than 500 full cycles, for example) but it will be increased by calendar fading over 8 years (LG's tests would take only a few weeks, not years, and they make no claim about calendar fade).

I can easily imagine the Bolt battery being down 40% after 8 years if treated harshly (for example, fully charged, allowed to sit for a few days, and fully discharged, this pattern repeated for 100,000 miles/8 years)

 

[Anonymous]

Toyota was way ahead of the curve with the Prius and yet virtually skipped BEV's altogether!

What if they are right and hydrogen is the answer.

Will we then care about the Bolt EV's battery mileage 8 years from now?

If the new Leaf gets 150 miles and the 8 year old Bolt EV gets 150 miles, what's the difference?

If 8 years from now, as part of the cost of financing solar for my home, what if I put my Bolt EV battery in my garage to maintain a nighttime energy source and get a new fresh battery for my Bolt, am I ahead of the curve?

And during these 8 years I did not have to "baby" my battery by turning my 230 miles Bolt EV into a lower capacity car and instead enjoy it to its full capacity while I am paying the most for it!

 

[SeanNelson]

If the OP is concerned about any sort of degradation telling them to always be charging, 100% as often as possible all the time is irresponsible or ignorant.

It's not as bad as all that.

First, the "100% charge" indicated by the Bolt is still less than the battery's true capacity because the engineers left a buffer at the top end of the charge range. This did this precisely because because they know that fully charging the battery is hard on it. So you already have a safety margin built in to the design of the car.

Secondly, while consistently charging to a higher level is likely to be harder on the battery, there's still a big question regarding how much harder it actually is. So far example, if after 100,000 miles of use you end up with 75% of the original capacity because you always charged to 100% vs. 80% of original capacity if you always undercharged it, then the result isn't exactly a catastrophe.

 

[SeanNelson]

Toyota was way ahead of the curve with the Prius and yet virtually skipped BEV's altogether!
What if they are right and hydrogen is the answer.
Will we then care about the Bolt EV's battery mileage 8 years from now?

Hydrogen was all the rage 10 years ago. Many jurisdictions announced "hydrogen highways", but they have pretty much withered on the vine. I very seriously doubt that the next 8 years is going to bring hydrogen back into vogue.

 

[cyaopec]

I guess Volt owners are good test subjects. My Volt has about 60k on the battery and I see no degradation. I used to get 10.4 kWh out of the battery and still get 10.4. If you google Teslas on the subject there are a few high mileage Teslas (including one that runs daily from Los Angeles to Vegas) with no where near 30-40 per cent degradation. I could live with 10% degradation at 150k miles and perhaps 20% at 200k. But if BEVs are really going to degrade 20-30 percent under normal consumer driving conditions at 100k miles, then current BEV technology is DOA. If you can get Volt like performance by keeping your battery between 25-75% charged that might work for early adopters. But no *normal* consumer would put up with such nonsense.

This is all very depressing . . .

 

[WetEV]

My Volt has about 60k on the battery and I see no degradation.

Doesn't mean that there wasn't any degradation. Just that the larger battery allows the car to hide it.

With a software change, the Bolt could do the same. Reduce the available battery to 42kWh, and there will be zero degradation visible to the driver.

 

[IMAdolt]

We don't know whether the battery has a buffer or not, look around, there's sources and testing done out there with conflicting information both ways, It seems like a no brainer to me to put in a 10% or so SOC buffer but it also seems like a solid corporate decision to make the battery have as high a range as possible with it's storage capacity despite all that just to be a market leader.

Unless a GM or LG chem engineer comes onto one of these forums or a news site and says so we can only guess.

We can also really only deal with the tech present to us at the time, we can't work of the possibility or likelihood of a hydrogen revolution or some other battery tech leap, there's lots of promising chemistries and battery designs out there, look up saline flow batteries or graphine aluminum or any number of other promising techs, the problem is we can't just wait for the next best thing because there will always be something possibly significantly better 5 years down the road.

If you want to get on-board, whatever your motivation, you deal with what's in front of you, or behind you or maybe what's in the immediate future. It's also a bad idea to bank on a replacement battery for any of these cars, unless you're buying a tesla or willing to build/refurb your own, Chev/Nissan/VW whoever it is isn't in the business of making you're 10 year old car good to go for another 10 years, they're in the business of selling new ones, the chance of an after market company making this happen is also pretty unlikely with as low a market share as we're looking at for the near future, until that changes.

 

[SeanNelson]

But if BEVs are really going to degrade 20-30 percent under normal consumer driving conditions at 100k miles, then current BEV technology is DOA.

Please don't take my example as gospel - nothing could possibly be further than the truth. I just picked those numbers out of the air to point out that "more degradation" isn't necessarily a show-stopper - it really depends on how much more we're talking about.

 

[Anonymous]

If the OP is concerned about any sort of degradation telling them to always be charging, 100% as often as possible all the time is irresponsible or ignorant.

It's not as bad as all that.

First, the "100% charge" indicated by the Bolt is still less than the battery's true capacity because the engineers left a buffer at the top end of the charge range. This did this precisely because because they know that fully charging the battery is hard on it. So you already have a safety margin built in to the design of the car.

Secondly, while consistently charging to a higher level is likely to be harder on the battery, there's still a big question regarding how much harder it actually is. So far example, if after 100,000 miles of use you end up with 75% of the original capacity because you always charged to 100% vs. 80% of original capacity if you always undercharged it, then the result isn't exactly a catastrophe.

Thank you Sean...

 

[Anonymous]

I have experience with battery fade. It happens!

Michael: It's been 100+ all week here in the San Fernando Valley and probably hotter in my garage!

If I am not always plugged in, as you suggest, then what triggers my Bolt EV's coolant system, to protect my battery pack?

 

[SparkE]

I have experience with battery fade. It happens!

Michael: It's been 100+ all week here in the San Fernando Valley and probably hotter in my garage!

If I am not always plugged in, as you suggest, then what triggers my Bolt EV's coolant system, to protect my battery pack?

Software.