Do lower-power Supercharger locations reduce strain on the battery pack?

[houstonian]

Title says it all - for any Tesla driver who's car can charge at v3/250kw does opting for an urban supercharger (i.e. 72kw max charge rate) or v1 reduce the strain on the battery pack when compared to charging at a v3 location?

Understand this is probably deep into the weeds for most folks but for those who do - or anticipate - heavily utilizing the Supercharger network, is any meaningful benefit achieved from opting to charge at lower speed superchargers over higher speed ones, when practical?

Goal is to be as gentle on the battery as possible while also being constrained to use the superchargers for a high percent of my charging needs.

Thanks.

 

[RayK]

If your goal is to minimize the damage done to the battery pack from DC charging, then I'd say, Yes, that using an Urban Supercharger is better than V3/250kW. I don't have any hard data but forcing higher power into a battery is generally seen as being harder on a battery than using something at a lower power. I've not L1/L2 charged my car for 3.75 years. I rely upon a CHAdeMO adapter (max. about 45kW) about 95% of the time, with 4% being an Urban SC and the other 1% being high power Superchargers when on a long trip. My estimated 100% range is just about 300 miles; varies between 268 and 271 miles at my normal 90% upper charge limit (27K miles on a 2018 LR RWD). I usually let the battery get down to about 50% and then charge back up to 90%. Since I'm not driving that much anymore, it's 2 to 3 weeks between charges for me so I don't believe that this qualifies as "heavy" usage in your definition but that's my data point from somebody that has exclusively DC charged for some time.

 

[fholbert]

Title says it all - for any Tesla driver who's car can charge at v3/250kw does opting for an urban supercharger (i.e. 72kw max charge rate) or v1 reduce the strain on the battery pack when compared to charging at a v3 location?

Understand this is probably deep into the weeds for most folks but for those who do - or anticipate - heavily utilizing the Supercharger network, is any meaningful benefit achieved from opting to charge at lower speed superchargers over higher speed ones, when practical?

Goal is to be as gentle on the battery as possible while also being constrained to use the superchargers for a high percent of my charging needs.

Thanks.

If you read about prolonging the life of your battery, it states to minimize the use of Super Chargers.

 

[houstonian]

If you read about prolonging the life of your battery, it states to minimize the use of Super Chargers.

Right as rain @fholbert.

And if you read my OP, you’ll note the context of “constrained” in that SCing is the only viable alternative to charge for my anticipated needs.

But as I also anticipate having some leeway in choosing SCers, I was curious as to if one option was less stressful on the battery than the other.

 

[houstonian]

@RayK - excellent post; thanks. The only other response so far missed the point.

I’m in RE with assignments from OR to FL so many miles on the road where SCers are my only option.

Go out of my way to use hotels with L2 chargers - and those helps - but does not fully address charging needs.

Will seek to first use UrbanSCs and V3 last when fate and circumstance compel supercharging.

 

[ucmndd]

If you read about prolonging the life of your battery, it states to minimize the use of Super Chargers.

Pretty sure Tesla says nothing of the sort.

Supercharge all you want. Is it worth waiting twice as long at a 72kw chargers to maybe have 9% battery degradation after 5 years instead of 10%?

Heck no.

Just hit 170,000 miles on my Model S. Have supercharged hundreds of times for many tens of thousands of miles. Degradation: 15%. Oh well. That 15% degradation has had essentially zero practical impact on my trips and driving. If anything I get down to the bottom of the battery faster now where it supercharges faster.

 

[stopcrazypp]

Title says it all - for any Tesla driver who's car can charge at v3/250kw does opting for an urban supercharger (i.e. 72kw max charge rate) or v1 reduce the strain on the battery pack when compared to charging at a v3 location?

Understand this is probably deep into the weeds for most folks but for those who do - or anticipate - heavily utilizing the Supercharger network, is any meaningful benefit achieved from opting to charge at lower speed superchargers over higher speed ones, when practical?

Goal is to be as gentle on the battery as possible while also being constrained to use the superchargers for a high percent of my charging needs.

Thanks.

What battery pack do you have? The strain on the pack depends on C-rate, which is the kWh capacity of the pack divided by the kWh speed. Higher C-rate theoretically does mean more wear than a slower rate, but temperature also plays a factor, as does the SOC range (what SOC are you charging in between?)

And by "heavily" how much supercharging are you talking about? How much percent of your charging (in terms of energy) would be supercharging? That makes a difference. It may be the case you still don't charge enough for it to make a significant difference. Also, don't forget batteries have calendar wear too (wear simply from battery sitting around), which sometimes can play the primary role. As such some tests show faster cycling actually results in less wear, but that's because the tests didn't account for calendar wear (the battery in those tests simply are younger because they finished accelerated testing faster, and calendar wear was the controlling factor).

 

[Olle]

A straighforward way to think about this is to consider what wears most on your battery during charging: Time and temperature spent at maximum voltage.

Take a look at this Model 3 supercharging curve. The downward slope of the charge curve starts exactly when the first brick reaches its maximum allowed cell voltage. The charge curve changes from constant power to constant voltage. As you can see, a V3 charging session spends more time than an ”Urban” session at maximum cell voltage. Maximum allowed temperature too is likely reached earlier in the V3 session, adding another multiple to the wear on your battery.

Another interesting detail that you will see in the 72 kW session is that if you were to stop at 70% SOC, you will not reach max voltage and thus have non of the typical supercharger wear.

Btw, your thermal management will likely work harder in V3, especially if it's outside with the sun beating on the car.

 

[golferguy]

If you read about prolonging the life of your battery, it states to minimize the use of Super Chargers.

"It states". Please provide a link.

 

[houstonian]

Supercharge all you want. Is it worth waiting twice as long at a 72kw chargers to maybe have 9% battery degradation after 5 years instead of 10%?

Heck no.

Just hit 170,000 miles on my Model S. Have supercharged hundreds of times for many tens of thousands of miles. Degradation: 15%. Oh well. That 15% degradation has had essentially zero practical impact on my trips and driving. If anything I get down to the bottom of the battery faster now where it supercharges faster.

@ucmndd - can report similar trend with my 2017 S75D; SC’d ~25% of the time and had ~11% degregation over ~215k miles.

Yesterday I was in Plano/Allen (North DFW area for all you folks reading along at home) and had several SCs to choose from before heading up to Amarillo. Opted for the Plano Urban SC as it’s close to dining, I wanted lunch, and needed to knock out some work...so in other words a longer charge time benefited me here.

This got me thinking if there was any if any material reduction on battery strain is realized by opting for lower speed SCs (or even 45kw CHAdeMO as @RayK notes in his post), when practical.

Not at all shy to charge to 100% or get close to 0%, but when I do so, the car never stays long at that level (i.e. I start driving as soon as I get to 100 or start charging immediately when stopping with a low %).

FWIW a ~5% → 100% takes ~1h10m on V3 and ~1h40m on an Urban SC for my X.

Stats from my S:

 

[RayK]

This got me thinking if there was any if any material reduction on battery strain is realized by opting for lower speed SCs (or even 45kw CHAdeMO as @RayK notes in his post), when practical.

Note: I'm retired - I can afford to spend time at the ChargePoint CHAdeMO station. A few days ago I charged the car when it displayed 128 miles of estimated range; about 43%. I added 144 miles in 46 minutes when it stopped at 90%. That's 272 miles. Or a bit more than 301 miles if fully charged. The car reported a maximum of 48kW, the most that I've seen in some time. It's usually in the low 40's but this time I preconditioned the battery before getting to the station. Air temperature was 73F and I was parked in the shade during charging. Here's the charging profile as recorded by my ChargePoint account:

 

[ucmndd]

Take a look at this Model 3 supercharging curve. The downward slope of the charge curve starts exactly when the first brick reaches its maximum allowed cell voltage.

Can you explain what you mean by this in more detail? Are you saying one of the bricks in the battery is fully charged at 20% pack SoC?

 

[Olle]

Can you explain what you mean by this in more detail? Are you saying one of the bricks in the battery is fully charged at 20% pack SoC?

Sure. Open circuit voltage (OCV) is a function of SoC in a cell, which you are probably familiar with. Because of the resistance in a cell, the charging voltage differs from OCV as a function of charging current.

OCV+ΔV_Chg=V_Chg, which has to stay below max allowed voltage (just over 4 V in ternary cells), else the cell would be damaged. At 250 kW, a Model 3 LR (the one in the chart), the charge current x cell resistance =ΔV_Chg fills the gap between OCV and V_max at around 20-25% SOC. From that point on, the charge goes slower and slower as ΔV_Chg and consequently charge current shrink with rising OCV from rising SOC .

A brick is a parallel group of cells btw.

 

[ucmndd]

Sure. Open circuit voltage (OCV) is a function of SoC in a cell, which you are probably familiar with. Because of the resistance in a cell, the charging voltage differs from OCV as a function of charging current.

OCV+ΔV_Chg=V_Chg, which has to stay below max allowed voltage (just over 4 V in ternary cells), else the cell would be damaged. At 250 kW, a Model 3 LR (the one in the chart), the charge current x cell resistance =ΔV_Chg fills the gap between OCV and V_max at around 20-25% SOC. From that point on, the charge goes slower and slower as ΔV_Chg and consequently charge current shrink with rising OCV from rising SOC .

A brick is a parallel group of cells btw.

Thanks for that.

How does this play out in cars that have a fatter charging curve and maintain peak power at higher SOC? Are they allowing a higher v_max? Different cell chemistry allowing a higher v_max? Just accepting a higher v_max and any longer-term degradation effects that might cause?

Pack architecture related somehow (400 vs 800v)?

 

[Olle]

Thanks for that.

How does this play out in cars that have a fatter charging curve and maintain peak power at higher SOC? Are they allowing a higher v_max? Different cell chemistry allowing a higher v_max? Just accepting a higher v_max and any longer-term degradation effects that might cause?

ΔV_Chg and Internal resistance are the chief variables that determine the slope of the highest possible charge curve. The absolute value of V_max falls out of the taper equation, when targeting 100% SoC where ΔV_Chg needs to end up at 0, which is the definition of 100% charge in a li-ion cell.
There is a trade off between resistance and energy density. Chemistry, like you say, is part of it. Cells with a high flat charge curve are optimized toward low internal resistance. This lets them retain a high current as OCV→V_max and ΔV_Chg →0. Also, Tesla as we know lets us charge to 100%, current will end up at 0 no matter how low the resistance. For a manufacturer that calls 90% 100%, the curve ends at some current >0 and thus looks flatter.

Intrinsic V_max is a pretty sharp limit for instant degradation that you can't cross for more than a fraction of a minute. Some manufacturers may want to play Russian roulette and get closer to V_max, relying on predictive BMS in the car and tight voltage regulation at the charger. Extra risky at third party chargers.

Pack architecture related somehow (400 vs 800v)?

The purpose of higher pack voltage is to save conductor cost and weight. For the case that pack voltage is in fact the limiting factor of your charge power, it shows in the peak plateau and not in the slope of the charge curve.

 

[geordi]

I'm at about 90% supercharging in my use of my cars, and have not seen more than a couple percent loss in 60k miles over the last year.

What puts wear on the battery is leaving it at 100% for extended time (several hours) rather than unplugging and getting going, or leaving it below 10% for any extended time. If you can plan out your usage to stop for a night with a partial charge that is above 20%, charge up to 80% overnight at that L2 destination... That will minimize the battery's time at any extreme when you aren't also simultaneously getting right back on the road with it. THAT keeps it in the thermal happy place, which also minimizes the wear.

Just use the thing, the car will manage the charging if you don't leave it to sit at either extreme.

 

[ucmndd]

What puts wear on the battery is leaving it at 100% for extended time (several hours) rather than unplugging and getting going, or leaving it below 10% for any extended time.

This is like 95% wives’ tale. Storing at 100% for many many hours isn’t really a problem until things get very hot, and it’s not much different from 90 or even 80%.

There is NO wear whatsoever from storing cells under 10% (so long as we’re not talking about a true zero%)

 

[geordi]

This is like 95% wives’ tale. Storing at 100% for many many hours isn’t really a problem until things get very hot, and it’s not much different from 90 or even 80%.

There is NO wear whatsoever from storing cells under 10% (so long as we’re not talking about a true zero%)

Ok... So if what I said is nonsense, then other than letting it go dead and leaving it there, what DOES hurt the battery? B/c my S has 50k miles on the new battery and already has 922 cycles on it, and is showing 1.6% degradation.... While the X has 1220 cycles and 127k miles (original battery) and is showing 14.3%. And that has jumped 2% in the last month, I bought it with 11.6% in February, 20k miles ago.

I'm not storing them at all obviously, but when I know they will be parked for more than a few hours (like when I'm actually at home rather than on a road trip) I'll cut the charge percentage back to 50%. The S hasn't been driven since February (when it was damaged and why I bought the X) and it hasn't shown any age on the battery while sitting, b/c it was at or above 50%.

I don't store the cars, but I DO use them fairly heavily, asking them to tow or supply the AC for camping for sometimes a couple weeks at a time while driving around for work. I try to avoid going below 10% before charging, but the distances to chargers - especially out west - makes that VERY difficult and there have been a few 100%-to-3% cycles on both cars because of that. Even now the X is showing me a 40 mile discrepancy between the rated range and the "real world" and I know the real world is STILL a bit higher than it would actually get.

Also for the Model S with 50k on the new battery - that's at least 90% supercharging for those miles. So if it was going to damage the battery.... I think I'd see it already.

 

[ucmndd]

Ok... So if what I said is nonsense, then other than letting it go dead and leaving it there, what DOES hurt the battery?

Mostly just the passage of time, and aggregate time spent at higher temperatures and higher states of charge.

B/c my S has 50k miles on the new battery and already has 922 cycles on it, and is showing 1.6% degradation.... While the X has 1220 cycles and 127k miles (original battery) and is showing 14.3%.

You are not defining a “cycle” correctly. A charge event is not a cycle - a cycle is a complete charge and discharge from 0-100-0, regardless of how many charge events.

Meaning two charge/discharges from 100% to 50% is “one cycle”.

Five charge/discharges from 80% to 60% is “one cycle”, and so on.

 

[geordi]

I know how to define a cycle - and that number I quoted is from Tessie, which pulls it from the car itself.

50k miles on the S from when I bought it, and was almost entirely road trips, I was doing AT LEAST 2 charges a day, of anywhere from 60-80% each. The number does seem a bit high, but not out of range for that kind of mileage and usage. About 8k miles was towing a Jeep Liberty behind the car, so the range sucked. Like 100 miles to a charge sucking. So yeah, it was using a LOT of cycles then.