How worried do I need to be about the effect of DC fast charging on battery longevity?

[billy_at]

My home charging station hasn't arrived yet, so I've so far been using DC fast chargers while I wait for it to arrive. It's only been two days, and two charges. I always charge only to 80%.

I've read that DC fast charging can reduce the lifetime of the battery. But how serious of an effect will it have?

Once I have the charging station, I plan to pretty much charge exclusively at home and use DCFC stations only on the occasional road trip.

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[Pibbman]

You’re probably fine. I think they say that in the context of using it almost exclusively. Unless you’re pushing off the home charger until next year you’re likely fine

 

[DaMeatMan]

It really depends on the speed as well and "DC fast charging" is a pretty relative term. With that said you could charge exclusively with up to 50Kw DC "fast chargers" and still be well within specifications of charging the cells at half their C rating for everyday charging. I actually do this myself and rely on 50KW charge stations exclusively since I live in a condo.

In other words the Mach-E with extended range battery is roughly 100 Kwh, and a 1C rating basically means charging at 100KW, 1.5C would be 150KW and so on. For lithium batteries in general, charging at rate that is up to half their capacity is standard practice for everyday charging.

Anything above 0.5c (in this case 50KW) would be considered detrimental to the life of the battery. That being said, even if you charge at a 150KW hour charger pretty often, that peak rate of 1.5c is only sustainable at lower battery levels when the pack is below 30% where higher rates of charge have minimal risk of degradation, after that the BMS (battery management system) starts to ramp down the charge rate such that you are actually charging at 1c to 0.8c for the majority of the charge cycle until you hit 80%, since it is at these higher states of charge where a high rate of charging has the most impact on the degradation of the cells.

And even when you hit 80%, your not actually hitting the true 80% capacity of the pack since only 88Kwh out of the 100Kwh pack is allowed to be usable, which means even when you charge to 100%, you've actually only charged the individual cells to about 88% of their actual capacity. When you also consider the fact that the BMS severely ramps down charging speed to 12KW after 80%, you are never really at risk of doing any sort of significant damage to the cells even if charging on the fastest DC fast charger possible due to how incredibly conservatively Ford has programmed the BMS to take care of the life of the battery.

All of this is a really long winded way of saying that Ford is doing allot here to ensure that battery degradation would be kept to an absolute minimum, and you can go nuts and fast charge whenever you like without worrying about doing any significant damage to the life of the battery. Not to say that there will be no degradation, but the degradation will be minimal and the life of the pack will far outlive the warranty on the battery.

 

[gafear]

I'm not sure why people even mention that. Ford warranty guarantees that the battery will maintain at least 75% of its capacity by 8years /100k miles

Use as much DC as you need, if it decreases the battery life just get a new one under warranty

 

[RonOinAZ]

https://www.ford.com/buy-site-wide-content/overlays/mach-e-overlays/mach-e-faq/
What is the warranty on the Mustang Mach-E?

Our New Vehicle Limited Warranty will help give you peace of mind with the following:

• Electric Vehicle Component Coverage: 8 years or 100,00 miles (whichever occurs first), with retention of 70% or more of the original High Voltage Battery capacity over that period.⁷
• Powertrain coverage: 5 years / 60,000 miles⁷
• Bumper to Bumper coverage: 3 years / 36,000 miles⁷
• Safety Restraint System coverage: 5 years / 60,000 miles⁷
• Corrosion coverage (Perforation only): 5 years / unlimited miles⁷
• Electric Vehicle Roadside Assistance Program: 5 years / 60,000 miles⁷

⁷ Whichever comes first. See dealer for details.

 

[stroszek]

A battery that declines more than 30% is almost certainly defective, the reason to baby your battery is so it only declines 5 percent instead of 10 (don't take these numbers I made up seriously).

 

[shutterbug]

My home charging station hasn't arrived yet, so I've so far been using DC fast chargers while I wait for it to arrive. It's only been two days, and two charges. I always charge only to 80%.

I've read that DC fast charging can reduce the lifetime of the battery. But how serious of an effect will it have?

Once I have the charging station, I plan to pretty much charge exclusively at home and use DCFC stations only on the occasional road trip.

Assuming you get your charger in a few weeks, I'd be more concerned with the cost of the DC charging.

 

[RedStallion]

Nothing really to be afraid of, It will kill the battery only after about 500 full charges. Typically the battery is considered dead after the capacity drops to 80%. Ford allows the capacity to drop to 70% (I guess from already 10% reduced value) before it will consider warranty replacement.

 

[RonOinAZ]

For what it's worth, here's what Ford's warranty says about battery replacement. In the event of a covered failure, receiving a "new" battery isn't guaranteed:

https://www.fordservicecontent.com/...E-Warranty_version-1B_frdwa_EN-US_11_2020.pdf
The high voltage battery and eDrive systems of your vehicle are
covered by the Electric Vehicle Component coverage for eight years or
100,000 miles, whichever comes first. High voltage battery and eDrive
components covered by this warranty include the high voltage battery
assembly, Bussed Electrical Center (BEC), Battery Energy Control
Module (BECM), on-board charger, Inverter System Controller (ISC),
DC/DC converter, and eDrive. If a covered component requires
replacement under the Electric Vehicle Component warranty, it may be
replaced with a new, factory remanufactured, or factory refurbished
component, at Ford’s discretion. Refurbished battery components
selected for your vehicle will align with your vehicle’s age and mileage
and meet Ford’s requirements and standards.

 

[gafear]

70%, thanks, for some reason I thought it was 75%

But again, it is enough security that you shouldn't care about battery going bad, you will get a new (or a refurbished which will have warranty just like new). Charge as much as you need to be comfortable and without range anxiety. This is a $50-60k car and you should use it all functions to the max and not be afraid of marginal impact in the battery

 

[praxiscat]

I wouldn't be too worried. There are people out there who just use fast chargers. Likewise the battery stopping at 80% is a way to prevent battery degradation as is the fact 88 out of the 99 kWh of the battery are usable. This is not something you are going to see out of the gate, and even then its not that severe.
Likewise try to find level 2 chargers in your area near grocery stores, movie theaters, etc. Since I got back from a road trip I have yet to to use a DCFC, and have used level 2 chargers exclusively. I don't have a charger at home. There is a free (on weekends and in the evenings) parking garage about a half mile from me with level 2 charging. Keep in mind, I live in a city. The weird part is they keep adding chargers around me.

 

[jlauro]

A battery that declines more than 30% is almost certainly defective, the reason to baby your battery is so it only declines 5 percent instead of 10 (don't take these numbers I made up seriously).

I have yet to see a phone without a defective battery after 5 years if you go by that 30% rule.

 

[engnrng]

Nothing really to be afraid of, It will kill the battery only after about 500 full charges. Typically the battery is considered dead after the capacity drops to 80%. Ford allows the capacity to drop to 70% (I guess from already 10% reduced value) before it will consider warranty replacement.

Where did you get 500 full charges from? Can you cite some test results?

 

[engnrng]

I have yet to see a phone without a defective battery after 5 years if you go by that 30% rule.

5 years, daily charging = 1825+ charges. Sounds about right. Now, take 2 full charges a week on an EV (500 miles every week - someone with a LOT of use/commute - yes, there are some that put 25,000 miles per year on a car) and the equivalent of 1825 charges is 19 years. I am not worried about the battery - the wheels will fall off much sooner...!!

And, that is assuming the battery management system on an EV is as primitive as the one on a phone! My company builds an EV off-highway equipment that we project 2500 to 3000 full charges to stay above 80% original usable capacity.

 

[RedStallion]

Where did you get 500 full charges from? Can you cite some test results?

It's a common knowledge, high capacity Li-ion batteries have a lifetime in 500-1000 range. LG Chem don't publish the numbers though, but they never claimed any miracle either.
I already provided the reference to the study that shows the batteries are dead after just 20 cycles without temperature management: https://news.ucr.edu/articles/2020/03/11/fast-charging-damages-electric-car-batteries
The goal is to achieve a million mile battery, best current numbers I've seen is about 300,000 miles, which is about 1000 full cycles.

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