Tesla now recommends charging to 80% daily instead of 90%

[Mach-Lee]

Just like the Mach-E, Tesla previously recommended a maximum daily charge limit of 90% to prevent battery degradation. However, they have just lowered their recommendation to 80% in the latest update (applies to NCA packs, not LFP packs):

Of course there is no official word from Tesla why the daily charge limit was lowered. But you can infer that there was probably too much pack degradation happening at 90%. Lower is better when it comes to charge limits—the lower the limit the longer the pack will last. Maybe they were getting too many warranty pack replacements?

Tesla lowering the limit to 80% is sort of a big deal because they are dominant in the industry and have some of the best battery experts in the world. If Tesla lowers their limit to 80%, I bet a lot of others in the industry will eventually do the same, including Ford. Rivian currently recommends only 70% for daily use.

Unfortunately, Ford doesn't educate the customer about high charge limits through intelligent user interface design like the Tesla app. The 90% recommendation is buried in the manual, and it doesn't help that the Mach-E still defaults to 100% and doesn't have a global charge limit setting.

I should note the "real" SoC for a given charge limit can vary significantly from manufacturer to manufacturer, so 80% displayed on a Tesla could be like 90% on a Mach-E or 75% on a Rivian in terms voltage level.

For more information about why high charge levels degrade lithium batteries (and why you should set your limit as low as possible), see the below Tweet and YouTube video:



More detailed scientific information about battery degradation can be found in this video.

P.S. - Still bothers me that Ford isn't more proactive about limiting pack temps while parked, nor enforcing global charge limits since both of these factors can significantly degrade lithium cell capacity.

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[MachA]

The lack of a global charge limit on the Mach E is a serious problem and a huge oversight IMO. It can lead to much unnecessary degradation for no reason at all, at least with the way I use my car.

 

[KevinS]

Do other manufacturers have a buffer like the MME does, or do they have availability to the entire battery capacity?

 

[AZBill]

For me personally, I am happy with having the location based limit. I am fine with allowing up to 100% when traveling. My Bolt, which I no longer have, had two limits, but I did not use the away one. My Rivian has only one global limit, which I do not like, because I have to manually set and reset it on trips.

100% occasionally, and when it is not stored for long times at that level, is not a big deal. In fact GM has a departure time setting that allows the car to complete the charge at departure time, so that it does not sit at the target charge limit for a long time.

 

[Mrn]

I've been using 40% 70% limits for my car since receiving it. That was based on research showing Lithium ion battery lifetime equivalent cycles being the greatest when staying near the middle of the batteries capacity.

It works for me since I don't drive very far on a typical day.

 

[voxel]

Do other manufacturers have a buffer like the MME does, or do they have availability to the entire battery capacity?

All do but some EVs have fairly small buffers like the Ioniq 5 and to some degree the Teslas.

A few things.

1) Mach-E has a large buffer compared to other EVs so maybe that's why Ford doesn't have an 80-90% rule?

2) Rivian recommends 70% for daily and warns of low regen even around 80-85% which is crazy because with Teslas don't unless the SoC is near 95% and no warnings at all in the LFP-based Model 3 RWD (probably because single motor regen is low). I've heard the Rivian buffer is tiny and folks only driving 3.5 miles after 0 so it make sense that the regen warning would appear around 85%

 

[SWO]

It's already been mentioned but the Mach-E having a relatively large buffer whereas the Tesla has a relatively small one is an important factor in the equation. Ford is already super conservative so I don't see them changing. That said, I usually charge to 80-85%.

Coincidentally, Bjorn has a new video up where he tests a 2021 M3 (Freemont build) with <60k mi and 16% degradation.

 

[mkhuffman]

All do but some EVs have fairly small buffers like the Ioniq 5 and to some degree the Teslas.

A few things.

1) Mach-E has a large buffer compared to other EVs so maybe that's why Ford doesn't have an 80-90% rule?

2) Rivian recommends 70% for daily and warns of low regen even around 80-85% which is crazy because with Teslas don't unless the SoC is near 95% and no warnings at all in the LFP-based Model 3 RWD (probably because single motor regen is low). I've heard the Rivian buffer is tiny and folks only driving 3.5 miles after 0 so it make sense that the regen warning would appear around 85%

This ^^^^

I think Tesla has almost no buffer. Same for Rivian. Our MME has a 4-5% buffer at the top. So charging to 90% is similar to charging to 85%. If Ford were to give us all the battery to use, they should also lower the recommended charge target.

I do agree that lithium batteries will last longer if you keep them within a tight range around 50%. But it is a car, and I don't like having the battery so low in case I need to take an unexpected trip.

Since my mom passed away, the need for an unexpected trip has significantly decreased, so I am not keeping the battery between 80% and 90% like I used to. But I still charge to 90% when I plug in, and 100% right before a trip out of town.

Range anxiety is a real thing, and public charging sucks. So the battery in my MME will just have to deal with a higher charge level.

 

[dj_stang]

The issue I have is power feels significantly reduced at the recommended SOCs. I only charge to 90% daily but I feel a linear lack of power as SOC goes down, and markedly less power even when you get to 87% and below. I have yet to positively confirm with my OBDLink, but that’s been my experience. Does anyone else (preferably with a GT or GTPE) notice the same?

I don’t think it’s due to heat because it feels the same even when the car has been sitting. For example, go to work at 95, come back at around 90-92, arrive at 85 or so.

 

[Mach1E]

The issue I have is power feels significantly reduced at the recommended SOCs. I only charge to 90% daily but I feel a linear lack of power as SOC goes down, and markedly less power even when you get to 87% and below. I have yet to positively confirm with my OBDLink, but that’s been my experience. Does anyone else (preferably with a GT or GTPE) notice the same?

I don’t think it’s due to heat because it feels the same even when the car has been sitting. For example, go to work at 95, come back at around 90-92, arrive at 85 or so.

Could be just in your head, or a coincidence of other factors (external temp, battery temp etc).

Luckily with the GT you don’t have to guess if power is limited. Just look for gray bars on your power meter.

SoC gray bars don’t seem to show up for me until below 60-70%. Someone who drives more than I do could probably chime in with an exact number. I rarely get below 70% and charge to 90%.

 

[mkhuffman]

Could be just in your head, or a coincidence of other factors (external temp, battery temp etc).

Luckily with the GT you don’t have to guess if power is limited. Just look for gray bars on your power meter.

SoC gray bars don’t seem to show up for me until below 60-70%. Someone who drives more than I do could probably chime in with an exact number. I rarely get below 70% and charge to 90%.

I have noticed that the gray bars appear earlier in the winter, when the ambient temperature is cold. In the summer, I also can get down to the 60% range before I see gray bars. In the winter, I start seeing them when it drops below 80%.

 

[dj_stang]

Could be just in your head, or a coincidence of other factors (external temp, battery temp etc).

Luckily with the GT you don’t have to guess if power is limited. Just look for gray bars on your power meter.

SoC gray bars don’t seem to show up for me until below 60-70%. Someone who drives more than I do could probably chime in with an exact number. I rarely get below 70% and charge to 90%.

Won’t deny the placebo effect could be coming into play, but “I don’t think that’s happening”

Gray bars are entirely separate though. Powering up your car at 50% won’t display any gray bars in my climate (although at lower SOCs they will), yet power will be quite a bit lower than at 100%.

 

[Mach1E]

Won’t deny the placebo effect could be coming into play, but “I don’t think that’s happening”

Gray bars are entirely separate though. Powering up your car at 50% won’t display any gray bars in my climate (although at lower SOCs they will), yet power will be quite a bit lower than at 100%.

You sure you don’t have gray bars at 50%? I’ve only been there a few times but in pleasant weather (80 degrees) the bars showed up right away even at low speeds (45 mph). There are many many factors that affect the gray bars though.

Either way, I’ve never felt power limited when the bars were not present and vice versa.

 

[kodiakng]

i just want to know how to get my preferred HVB SoH curve:

?

 

[Mach-Lee]

I think Tesla has almost no buffer. Same for Rivian. Our MME has a 4-5% buffer at the top. So charging to 90% is similar to charging to 85%. If Ford were to give us all the battery to use, they should also lower the recommended charge target.

I do agree that lithium batteries will last longer if you keep them within a tight range around 50%. But it is a car, and I don't like having the battery so low in case I need to take an unexpected trip.

That is a good point about the buffers being different Mike. I don't know what voltage levels correspond to what % in a Tesla, but here's what they are in the Mach-E:

Displayed SoC	Pack Voltage	Volts/cell
70%	363 V	3.86 V
80%	371 V	3.95 V
85%	375 V	3.99 V
90%	380 V	4.04 V

In the video, the battery scientist recommended keeping the cells below about 4.06V (what he calls 75%) for maximum longevity. It would appear Ford is tracking closely with that recommendation at the 90% level, so I think 90% is still okay for daily use in the Mach-E. And yes, it would be nice if Ford could give us an extra 5-10% from the buffer for trips, but they would have to guard that much better with software controls so it can only be set per use.

I'd be curious to know what the cell voltages are in a Tesla at 80% vs. 90% for comparison.

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