How much DCFC is too much?

[GrumblesTheDog]

Hi folks. I don't think I saw a dedicated thread for this, just individual posts about good battery management practices.

Does anyone have a sense of how much DC fast charging you'd need to do to result in noticeable battery degradation/capacity loss? I'm curious, since the MME has proven itself to be a very nice road-tripping car (and will be even moreso when BlueCruise launches) to the point that I've probably already charged around 700kWh on DCFC stations since I got mine. It's certainly a phenomenon in Teslas despite their thermal management, since they can limit your supercharger max rate, apparently, if you DCFC enough to result in battery degradation. That said, the one source I saw describing this said it happened to someone who'd put on thousands, if not TENS of thousands of kWh through DC fast charging.

I get that there's probably no threshold, but is the general principle the same as Tesla and supercharging? Or is the MME battery chemistry/management sufficiently different that you shouldn't need to worry about it unless you DCFC daily, for example (or some other extreme scenario like that)?

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[Murse-In-Airy]

I have no data. But I’m betting THIS is the reason we have the “slow charging curve” that people have been complaining about. AND the limit that we can’t DCFC above 80% (that people are also complaining about). So I’m not worried at all.

 

[timbop]

I have no data. But I’m betting THIS is the reason we have the “slow charging curve” that people have been complaining about. AND the limit that we can’t DCFC above 80% (that people are also complaining about). So I’m not worried at all.

agree with that sentiment. The chemistries of the M3 and MME aren't overly different, but as was pointed out Tesla pushes their batteries a lot harder. You're probably fine even if you do charge 10% to 20% of the time on DCFC, assuming that you only charge to 80% or 90% on L2. Of course that is all speculation, but it would be consistent with Ford's conservative approach

 

[theo1000]

I wouldn't worry about it at all. The only thing that matters is what the base cells see. The battery design is based on the Volt. My 10 kwh volt charging at 3.3 kw is the equivalent of running the mache 88 kwh battery at 40-50 kw. I have about 4,300 100% charge cycles on my Volt with no large degradation. Just last weekend my 12 year old volt gave me 39 miles of a original 33 mile rating. You could dcfc the MachE everyday 0%-80% or even 100% for 10 years and you would still get over EPA range.

 

[mr_raider]

I wouldn't worry about it at all. The only thing that matters is what the base cells see. The battery design is based on the Volt. My 10 kwh volt charging at 3.3 kw is the equivalent of running the mache 88 kwh battery at 40-50 kw. I have about 4,300 100% charge cycles on my Volt with no large degradation. Just last weekend my 12 year old volt gave me 39 miles of a original 33 mile rating. You could dcfc the MachE everyday 0%-80% or even 100% for 10 years and you would still get over EPA range.

In all fairness, the Volt never sees 0% or 100% charge cycles. GM keeps 4kwh in reserve that the user can't access.

 

[theo1000]

In all fairness, the Volt never sees 0% or 100% charge cycles. GM keeps 4kwh in reserve that the user can't access.

Neither does the 88 kw Mache. It has a 10 kw buffer as well as the 80% cliff so the last 20% actually charges at less than 50% of the Volt! cell level. It the same approach. The current EV from GM, Ford, VW, Audi, Porsche, Jaguar, Hyundai, Kia all have the same family designs with large buffers, excellent flat pack cooling and low cell level charging. I have a lot of confidence in that tree of engineers/engineering.

 

[ChasingCoral]

This is an important question to which we have no solid answer. You'll find some information on a this past thread:
https://www.macheforum.com/site/threads/does-dc-fast-charging-damage-batteries.2019/
in particular, a couple of scary articles about the damage from as few as 25 DCFC sessions. However, the Mach E has newer batteries, a 10% buffer, and the charge rate hits a cliff at 80%. It appears Ford has done a lot to avoid having to pay out on their battery warranty.

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