70% SOC/charge for "daily" vs. 80%

[gregtay]

Slightly off-topic, but I wish we could set charge limits based on location. We have chargers at work, so I usually charge to 85% every other day (M,W,F) at the office, but sometimes I'll charge at home if I end up driving a lot during the weekend, in which case I only charge to 70%. It doesn't actually take that long to change it through the UI, but it would be nice to set that up automatically.

Audi allows for this with the etron. Charging profiles based on location. Audi's software doesn't do much... but this was one feature they had implemented.

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[txtravwill]

I recall 30-70% as lithium being happiest so I usually use 60% for daily lately and cycle about 40-60% most days max, sometimes more.

 

[Mathme]

I charge to 80% when needed and I like to charge during the day (WFH here) as that way my solar panels offset the charging costs.

We drove back from the holiday trip Wednesday night and I only had about 80 miles of range left. My plan was to charge yesterday during the day to give more buffer to drive up to a local outside amphitheater for a concert last night (it's about 25 miles away each way). Low and behold PG&E (our crappy electric company) decided to have an outage at my place from 7-3 yesterday.

The easy-solution was a trip over to the local Walmart and use the EA supercharger for about 100 miles of range.

Morale of the story: sometimes it makes sense to use a local fast charger.

 

[mkg3]

My R1S w/ 22" wheels in sport mode w/ lowest ride height gives me a 285 mi range when charged 100%. I have a 100+ mile daily (6 days/wk) commute. If I were to charge only to 70% or 80%, that would only give me a 200 or 228 mile range and I'd have to plug in daily or if every other day, face range anxiety if any unexpected additional miles were required.

Are there any negative consequences to charging DAILY to 80%?

If so, then I'd prefer charging every other day to 90% for a 257 mi range.

This past year, I was involved in looking at hybrid electric turboprop aircraft. The part of the efforts included power density, charging cycles and management of parallel versus serial use of electric motor for most effective use.

In this process, every DOE, NASA and industry papers I looked at essentially said Li-Ion (liquid or air/solid state) batteries like to live between 20~80% range to maintain optimal operations.

Does it mean you cannot charge it to 100% or run it down to 5%? - No, of course you can. It's just that its should not live in those SOC. In other words, don't let your vehicle sit idle at 100% or below 20% for any significant amount of time.

 

[Steve A.]

This past year, I was involved in looking at hybrid electric turboprop aircraft. The part of the efforts included power density, charging cycles and management of parallel versus serial use of electric motor for most effective use.

In this process, every DOE, NASA and industry papers I looked at essentially said Li-Ion (liquid or air/solid state) batteries like to live between 20~80% range to maintain optimal operations.

Does it mean you cannot charge it to 100% or run it down to 5%? - No, of course you can. It's just that its should not live in those SOC. In other words, don't let your vehicle sit idle at 100% or below 20% for any significant amount of time.

Define *significant*. Hours? Days? Weeks?

 

[LevelHeaded]

They simply figure 70% is more than enough for most peoples’ daily driving.

This, combined with the fact that a battery sitting in your garage will experience less degradation the closer the SoC is to 50% at rest (calendar aging) is why they don’t just say “charge it to 100% daily;” it makes sense for them to recommend the lowest SoC they think (1) doesn’t sound crazy and (2) will satisfy a majority of users’ daily driving.

 

[mkg3]

Define *significant*. Hours? Days? Weeks?

The underlying assumption is that the battery is in use all the time. What I meant by significant is more than 24 hours/1 day.

If the vehicle is not being driven, definitely keep in below 80% or above 20% SOC. I've never read or heard anyone say 50% is optimal for storage/non-use. Not saying is or is not. It's probably just one of those intuitive ideas that has no real scientific basis. Or that I'm just ignorant about it.

 

[Trandall]

I charge to 90% because I charge infrequently, once or twice per week when I drive into the office. I don’t like going below around 50% ever (except on road trips) because of the loss of performance anyway.

You lost me on the loss of performance below 50%. Are you at the drag strip daily? Even for spirited driving I have not noticed any loss of performance until very low like <10%.
To the OP's original question all battery chemistries are not created equal and even among categories such as "LFP" or "NCM" many OEM's have varying chemistries that will have more or less plating on the anode when nearing full charge. I also think Rivian is being very cautious with this recommendation.
70% works for most daily driving for me but if I needed 85% SOC daily I wouldn't loose sleep. Since we now have the slider option I use 95% for road trips where I plan on DCFC'ing instead of 100%

 

[mikehmb]

You lost me on the loss of performance below 50%. Are you at the drag strip daily? Even for spirited driving I have not noticed any loss of performance until very low like <10%.
To the OP's original question all battery chemistries are not created equal and even among categories such as "LFP" or "NCM" many OEM's have varying chemistries that will have more or less plating on the anode when nearing full charge. I also think Rivian is being very cautious with this recommendation.
70% works for most daily driving for me but if I needed 85% SOC daily I wouldn't loose sleep. Since we now have the slider option I use 95% for road trips where I plan on DCFC'ing instead of 100%

I’ve not noticed any significant performance degradation at any SOC. It’s possible I’m driving too conservatively most of the time.

My solution, therefore, is hoon at every SOC. For Science.

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