20/80 Li Ion Charging

[Crissa]

I thought 4680 battery architectue is dry chemistry and is not governed by the same 80/20 rule. Is that not the case?

No, the dry chemistry is just a manufacture detail. We don't have enough data to know if it has any other benefits other than cost.

-Crissa

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[Crissa]

Your objection is worse than pedantic.

That is gibberish. It's not pedantry - it's that there's no evidence that trickle charging or quick charging is worse.

Why would charging at 1.7kW vs 11.5 affect the battery negatively, when the battery is over 75kWh?

-Crissa

 

[moeali]

No, the dry chemistry is just a manufacture detail. We don't have enough data to know if it has any other benefits other than cost.

-Crissa

One of the main selling points for the 4680 batteries was presented in the battery day was that the dry chemistry was
less prone to degradation.

 

[Diehard]

Apple literally pays you for the old phone.

-Crissa

didn’t know that. Do they pay as much as it cost me to buy a new phone? Because that is the cost of not being able to continue using my old one by changing my battery. Regardless of what apple does, their way always comes with more dependency because it is simply good business. That is the problem. I thought you were pro right to repair.

 

[Crissa]

One of the main selling points for the 4680 batteries was presented in the battery day was that the dry chemistry was
less prone to degradation.

I do not recall this anywhere.

-Crissa

 

[Crissa]

didn’t know that. Do they pay as much as it cost me to buy a new phone? Because that is the cost of not being able to continue using my old one by changing my battery. Regardless of what apple does, their way always comes with more dependency because it is simply good business. That is the problem. I thought you were pro right to repair.

If you're buying a new phone, then why do you need to use the old phone? It's an old phone.

If you're just replacing the battery, they send you the phone back after they repair or inspect it.

Replaceable batteries can't be used as structure, so I don't know how the EU rule is going to work out. Are they just going to have phones that are more prone to damage and failure?

??‍

-Crissa

 

[Diehard]

Replaceable batteries can't be used as structure,

Assuming you are correct, why do you think they should? I have owned phones with replaceable batteries and have never had a problem with their structural integrity. remember like this:

but If you don’t like this design, there are newer options to comply with EU requirements:

Even with EVs there are a Lot of them on the road with serviceable batteries. Granted, not serviceable enough for an average joe like me yet but serviceable enough so they are not all or nothing deal.

we can argue over whether one design choice is better for consumer or manufacturer but we can not deny there is a choice (At least for the manufacturer). I personally don’t mind paying a little more upfront to make sure my device is a little less disposable.

 

[HaulingAss]

That is gibberish. It's not pedantry - it's that there's no evidence that trickle charging or quick charging is worse.

Why would charging at 1.7kW vs 11.5 affect the battery negatively, when the battery is over 75kWh?

-Crissa

In the cold the BMS is current limited and cannot draw enough current to keep the battery at a good temperature. It's also very inefficient because it must try to keep the battery warm over a much longer period. When there is enough power available to charge at a higher rate, the charging itself warms the battery from the inside out.

In short, the BMS is programmed to maximize battery life and can do a better job of that in the cold when it is not limited to the 1400 watts of a 120V 15A outlet.

 

[Crissa]

In the cold the BMS is current limited and cannot draw enough current to keep the battery at a good temperature. It's also very inefficient because it must try to keep the battery warm over a much longer period. When there is enough power available to charge at a higher rate, the charging itself warms the battery from the inside out.

In short, the BMS is programmed to maximize battery life and can do a better job of that in the cold when it is not limited to the 1400 watts of a 120V 15A outlet.

No, the thermal system can draw as much power as it needs.

It has a battery.

I don't know what you're basing this upon. At a certain point, yes, you can't charge fast enough to keep it warm. But that's like at <-30F.

You don't need to have the 'optimal' temperature if you're charging slowly. Because there's more than enough battery to absorb the power.

-Crissa

 

[HaulingAss]

No, the thermal system can draw as much power as it needs.

It has a battery.

I don't know what you're basing this upon. At a certain point, yes, you can't charge fast enough to keep it warm. But that's like at <-30F.

You don't need to have the 'optimal' temperature if you're charging slowly. Because there's more than enough battery to absorb the power.

-Crissa

I'm basing it upon charging my Model 3 outside in the N. Cascades on 120V 15A circuit for an entire winter. The BMS is reluctant (at best) to draw the battery down further to begin charging in cold temperatures because it knows it only has 120V 15A to keep it warm and charge it back up. The system needs more power than that to keep up so the BMS ends up charging a cold battery. It's not going to instantly ruin it but it will degrade more than if the BMS had more power to work with. If it used the battery to warm the battery in such a siituation, you could wake up the next morning with less SoC than you went to bed with.

 

[Crissa]

It will not hurt the battery.

You need optimal temperature to absorb a higher C rate. Not to absorb a tiny C rate.

-Crissa

 

[JBee]

I'm basing it upon charging my Model 3 outside in the N. Cascades on 120V 15A circuit for an entire winter. The BMS is reluctant (at best) to draw the battery down further to begin charging in cold temperatures because it knows it only has 120V 15A to keep it warm and charge it back up. The system needs more power than that to keep up so the BMS ends up charging a cold battery. It's not going to instantly ruin it but it will degrade more than if the BMS had more power to work with. If it used the battery to warm the battery in such a siituation, you could wake up the next morning with less SoC than you went to bed with.

That would only be true if the power input from 120V is less than the heating power required to maintain battery temperature so it could charge.

At low temperatures the COP of the HVAC heat pump might be around 1 meaning there is no efficiency gain from the heat pump, so if the pack heating is using 1400W there's nothing left for charging.

Now I'm not sure what the specific heat on the pack level is, but pure lithium is quite high and needs around 14kWh for 500kg and a 20'C temp rise, so that alone would be 10 hours at 1400W. That's only to get it up without factoring in heat loss along the way.

Now if you had above freezing things start to get better fast, firstly because the battery is already capable of taking 1400W, plus the heat pump can double it's COP and the heat loss would be less from a lower delta t.

If someone can find the specific heat on a pack level we could find out the crossover temp, where it becomes a net negative to charge a battery. Or maybe someone already publishes that?

We'd also need to know the charge rate allowed for low temperatures.

 

[PilotPete]

What's the name of the company that runs between SFO and LA?

I gotta go look that up. I saw their data on battery status and overall maintenance. I think they have MSs. I’ll look it up when I can and post it back.

 

[HaulingAss]

We'd also need to know the charge rate allowed for low temperatures.

I think when all that is available is 120V 15A, it will be a little more likely to go ahead and charge without waiting for the battery to warm up as much as it would if higher power levels were available. I've seen it not charge at all below 20F for 2-3 hours and then start adding about 2 mph. IMO, this is a compromise because it realizes it can never get the battery very warm at such temperatures and with so little power to work with.

With 50A or 60A 240V available, it can follow a temperature/charge rate schedule that is more ideal for battery longevity. With low available charging power, Tesla knows how to compromise and spend a little battery longevity for the ability to add some miles in very cold weather without waiting an eternity.

I also think the charge algorithms can become more conservative with regard to battery longevity if a particular battery already has too much degradation, so there are no hard and fast rules, everything is on a sliding scale, trying to keep the charging power for any given temperature in the sweet zone without being excessively strict about not deviating from the absolute ideal if it will add more miles of range overnight without causing unacceptable levels of degradation.

 

[samueldion1]

The less you cycle the battery state of charge the longer it lasts. The cycle life can be orders of magnitude more if you do this.

So recharging it often for small percentages is better than charging it seldom and only when at 20%. Same for driving it from 80%.

It's worth noting here that the 20/80 isn't a hard rule or point, it's just from where it gets considerably worse in comparison. Other factors like rate of charge/discharge and temperature also play a role in how often you can cycle a battery.

Basically the less extreme the conditions and state change, the longer they last.

But all this should be taken with a grain of salt, as many new batteries haven't even been around long enough to test full real-life life cycles. There's some data to support this though, and that has been extrapolated.

My research over the years has found that Li Ion batteries charged to 80% maximum and discharged to no more than 20% have an ‘indefinite’ lifespan. I understand there are many other factors but that this is a fundamental of this battery chemistry.
Will CT (or do any Teslas) allow programming for an 80/20 regimen?
If so… and this is recommended to maintain battery pack life, the a 500 mile range CT would be reduced to a functional range of 60% of that or 300 miles. And a 300 mile range CT would be reduced to 180 miles if these ship with Li Ion packs.
Im having a hard time with this functionality against hybrid tech.
Thoughts?

I have driven Teslas exclusively for the past 4-1/2 years. You do not need to worry about range or degrading of the battery. My Model 3 had 325 miles of range when I started out in March 2019 and Tesla recommended not more than 80% charge unless I was planning a long drive. I followed this recommendation and by the time I traded in for my Model S at the end of August 2023, I had 69,000 miles on the Model 3 and the maximum range degraded to 295 miles. Needless to say, the 10% loss never was a problem either. 295 miles is plenty of range. Now I have 405-mile range in my Model S and I follow the same regimen. In summary, you don't need to sweat it. Range anxiety is just anxiety. It is not based upon reality. I'm sure you don't analyze your ICE car in terms of range, but when you have a "full" (80% or more) charge every morning before you leave home, you are not going to worry.

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