Charging to 100% at home vs Supercharging

[petecrayton]

What is worse for battery and leads to faster degradation? Let’s say I need to go 220 miles on my SR+, which would require me to charge to 240 miles/100% of battery capacity. Alternatively I can charge to 80% at home, which will give me 193 or so miles of range, probably ~170 of effective real world miles. In this case I would have to supercharge in the middle of the trip. What is better for battery?

This discussion can make your head spin and definitely take the "fun" out of the car. Maybe it is just enjoyable to contemplate, if you are a technocrat. After procuring my first 911 Turbo, it occurred to me that though I could afford to buy it, I couldn't afford to drive it, i.e. I felt the need to be so careful I couldn't experience the car's capabilities. So now I don't worry about preserving my battery. I plug and drive. When it wears out, I will get another one.

 

[Pilot1226]

Trade in for a LR? If this is going to be a long term habit.

However, if an SR+ has a 75/78KWh battery but limits a 100% charge to 58KWh of that 75KWh, wouldn’t BMS take care of the battery where 100% charge for SR+ is really only 58 of the 75? So their 100% is really not that big of a deal?

I think this may have been discussed before.

I can’t agree more. If you have a known daily commute that is pushing the limits of the vehicle, the LR is the way to go. There are multiple layers of stress here that become a non-issue for every single commute you do with an LR.

Yes, it’s more expensive, but if you’re going to spend 40k on an SR+ anyway, why not get an LR for around 8k more, which gives you comforts of the premium interior as well as the extra range which appears to be warranted here. We are talking around $1,250 a year for a 6 year loan. Your Supercharger fees will cut into the difference here.

Plus charging to 99-100% at a SuperCharger takes forever! Rarely do I ever stay past 70% while at a SuperCharger if I can get to the next one with anything over 15% if that makes sense.

I don’t think the OP is suggesting to charge to 100 via SC. I believe the OP was going to top off as needed for their commute including a buffer. Example, pull in at 40% charge, charge to 60-75%, and good to go.

Charging at home to 100% is “easier” on the battery (provided its 220v, not 110v) as long as you depart soon after fully charging. Supercharging will stress the pack more simply because of the dramatically higher rate of charge over the last 5%.

Realistically speaking though, it’s not a *huge* concern. It’s great to be mindful, but don’t stress about it. Go ahead and supercharge as needed, but don’t let the car sit at 100% for long - use that extra range as soon as you can and you’ll be fine.

Can you elaborate on why you feel 120V charging is bad for the pack?

 

[Drax]

@Pilot1226 Everyday charging using 120v is not a bad thing, though it is less efficient. The reason it’s not ideal for 100% charging is because your pack continues to sit at a higher state of charge for dramatically longer as the car approaches 100%.

Ultimately the goal should be limiting the time your SOC is over 90% and under 20%.

Hope that helps.

 

[Pilot1226]

@Pilot1226 Everyday charging using 120v is not a bad thing, though it is less efficient. The reason it’s not ideal for 100% charging is because your pack continues to sit at a higher state of charge for dramatically longer as the car approaches 100%.

Ultimately the goal should be limiting the time your SOC is over 90% and under 20%.

Hope that helps.

Makes sense. I’m figuring around a 20% efficiency loss with 120 vs. around 10% with 240.

 

[drdumont]

Although I have only had my "traveling" Model 3 since February, I have found that there's no reason to charge to 100% since I have SCs within 100 miles of my house. You may not.



My conclusion is that the car is smarter than I am, and I'm much happier letting it think for me. Except for FSD. I'll, drive, thank you very much... <ducking for cover>.

David, with what do you disagree?
That the A/C uses less energy in Recirculate?
That you don't want the car to think for you?
Or that I dislike the FSD?
I'd like to hear your thoughts...
I'm not trolling for a fight over FSD - if that is your issue, then fine, we disagree.

 

[PedramGh]

The difference in degradation we’re contemplating here is very, very small. Do what is the most convenient for you.

If the scenario is charge to 100% at home or a quick Supercharger session, I would always pick leaving at 100% to provide additional flexibility while driving. For example, if the weather is unexpectedly bad, you can always stop at the Supercharger later.

Remember! It's your car serving you. Not you serving your car. If your battery is degraded after 8 years you either upgrade your battery or your car...

 

[e-FTW]

I don't think that's quite accurate… or, at least not according to Tesla's battery consultant, Professor Jeff Dahn at Dalhousie University. He claims that time is the "bad actor," i.e., the slower a charge, the more TIME for the parasitic reactions to take place:

Couple of items I want to clarify after watching the whole thing (you want to stick around for Q&A): yes “time is the bad actor”, but that is for:

• Individual cells that are not temperature managed
• Running at high temps (40 Celsius and 60 Celsius. In Imperial units that is 104 and up)
• And at high voltages (which may represent a high state of charge).

The Tesla pack solves this with active cooling (unlike some other cars) and am sure the upper-limit on voltage is carefully set by Tesla.

I charge at 120v/12amps because that is my only option. I charge to 70-80% daily, and to 100% for long trips (I will simulate to see of going beyond 90% for a trip has a measurable time advantage. It probably does not, and you get to your coffee stop earlier).
Am not noticing a large drop in battery capacity.

 

[Atari2600]

Couple of items I want to clarify after watching the whole thing (you want to stick around for Q&A): yes “time is the bad actor”, but that is for:

• Individual cells that are not temperature managed
• Running at high temps (40 Celsius and 60 Celsius. In Imperial units that is 104 and up)
• And at high voltages (which may represent a high state of charge).

So your position is the only bad things you can do is keep the batteries under 10% or over 90%?

 

[Gasaraki]

What is worse for battery and leads to faster degradation? Let’s say I need to go 220 miles on my SR+, which would require me to charge to 240 miles/100% of battery capacity. Alternatively I can charge to 80% at home, which will give me 193 or so miles of range, probably ~170 of effective real world miles. In this case I would have to supercharge in the middle of the trip. What is better for battery?

Charge in the middle, get one charge in.

 

[e-FTW]

So your position is the only bad things you can do is keep the batteries under 10% or over 90%?

Yes. The battery pack appears to be quite skillfully managed by Tesla to avoid the issues that Professor Dahn described he saw in cells that are treated badly (by Nissan in 1st gen Leafs [Leaves?] for example).

Personally, I keep the charge to 70-80% at home. I crank it to 90-100 for trips exclusively.

 

[e-FTW]

(I will simulate to see if going beyond 90% for a trip has a measurable time advantage. It probably does not, and you get to your coffee stop earlier).

ABRP reports a 4 minute increase in total trip time for San Francisco to Bryce Canyon. For a 14:40:00 trip, that is a ridiculously low difference. So am going with 90% charge before leaving for a trip going forward.

Important note: I have seen nothing to indicate what amount of time spent at or near 100% is considered “bad” for a Tesla battery pack (not an abused cell in a lab). Is spending the night going from 90% to 100% measurably bad? Is “bad” on the order of minutes, hours, days, weeks? I would love to know.

 

[Atari2600]

If guess if you are going to charge often to 100 from home it might be useful to have a 48 amp charger then try to keep it over 90 for the least amount of time?

 

[Pilot1226]

Every lithium based battery tends to try to hold off on charging to max until the last possible moments to reduce stress on the battery and improve longevity.