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Some exciting observations about the new Model S60 (software limited 75 kWh)

Chopr147

Active Member
Apr 3, 2016
1,940
1,470
Wantagh, NY
If your theory is right, those 75 kwh put itself in a awkward position: worst $ spend for actual daily usage. why spend another $9000+tax for extra range only benefit a little in road trip?

This in a nutshell is why I think we do not have an answer from Tesla. If it is top limited why should Tesla make this known when they don't have to. They can still sell the 75kwh as a full 15 kwh more and 41 more miles than the 60. 41 more miles with a 75 can be the difference for some people. But if those same uninformed buyers learned it is actually only 15 more miles daily with the 90% charge , would they pay $9000? I know I wouldn't. So I don't have much confidence Tesla will give an answer to this question and I can't blame them.
When I purchased my 60D I did not even bother to entertain the thought of upgrading to a 75 and ignored that option completely.
Mainly due to TMC and the wealth of knowledge one can learn about a car. Geez, we have engineers and wanna be engineers calculating, crunching,researching and testing all manner of the tech in a Tesla. :)
 
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privater

2016 Model S and 2017 Model 3 owner
Jun 22, 2016
254
744
CA
Geez, we have engineers and wanna be engineers calculating, crunching,researching and testing all manner of the tech in a Tesla. :)

That's right, kudos for them!
And I concur with your assumption. It really put Tesla in a paradox position:
Locked top? it might agitate forever debate, S60 is essentially have an 20% battery buffer than others for free.
Locked bottom? bad customer experience, for an $70000ish EV, the daily usable range is around 160 Mi.
Maybe they find a neat solution on middle ground, who knows.
However, keep silent and keep the rights to change anytime might be the best option for them
 
Last edited:

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
The reason for the 60 was to create a low price of entry. Mission accomplished. Personally, I've seen more 75's, so someone is buying them. Nothing wrong with a 75 if you can afford it and need the extra range.

A neater way to handle the software limit would be a sliding window, where the "window" is in the middle most of the time, but when the BMS thinks the pack is out of balance, or on a set interval, it would slide the window up temporarily and force a balance charge. The only artifact would be that the user would see a longer than normal charge time. The CID could show a pop up to indicate that balancing is needed, and inform the user that it will add some time to the charge process, and ask for the user to decide if it's ok to perform it.

I think Tesla should do something like this to either automate an occasional 100% charge (all cars) or at least tell the owners to do it once in a while. There are people that NEVER do it and wonder why they are losing range.

The 100% charge also re-calibrates the BMS so it can better determine SOC and you get a more linear instrument.
 
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joeytree

Member
Jul 13, 2016
13
8
New Jersey
Someone correct me if I'm wrong but I believe this is due to a fundamental difference between Tesla and other EV manufacturers... Tesla actually permits you to make use of 100% of your battery if you so choose to do so. This is compared with nearly every other EV, including the Nissan Leaf and the BMW i3. In the case of the 24kWh Leaf, the cars systems actively manage things such that about 21.3 kWh is treated as 100% where in reality it's closer to 90%. It reserves/manages in this manner specifically for battery longitivity. Where as I think Tesla is treating us like adults, warning us about the tribulations of excessive charging, but letting us make our own decisions...
My understanding is that the LEAF is limited to discharge only 21.3 kWh. This is because discharging to true 0 would be very bad. VERY bad. I believe Something similar happens in the Teslas, but I can't find information on the exact number.

Another thing I've seen in Tesla posts here is that "0" miles left really allows you an 18-mile or so idiot buffer (so you don't get stuck if you really try to push the limit). While I can't vouch for that, I'm 95% sure this happens in the LEAF. I've run it down until everything is blinking, which is well under 5%. But I can see I've only used around 16.5 kWh when I check the app the next day. Even based off a 21.3-kWh discharge limit, I should have well over 4 kWh left. That's over 16% of the 24-kWh pack, let alone the 21.3-kWh discharge limit on which the % calculations should be based. So I tend to give credence to the reports of others that something similar happens in the Teslas.
 

joeytree

Member
Jul 13, 2016
13
8
New Jersey
I think that they are bottom limiting the new packs. This would explain how they can still balance a software limited pack, because it can still go to true 100%. This also means that 100% is really 100%, and you shouldn't do this daily. Ignore what the DS and Tesla Techs say, they are not engineers and have been proven to spew all kinds of incorrect information.

I'll start gathering proof for this as I can.

For now, an older 70 would be at about 343V when charged to 90%. I'll do some tests on a new 75 and see what it's voltages are, and then all we need is someone to report on a new 60.

Before anyone says it, the new battery cells can take a much higher charge rate, which explains why there is less taper.
See the posts on page 2 from privater:

Some exciting observations about the new Model S60 (software limited 75 kWh)

He has some charge date that only makes sense if the battery is top limited. Otherwise the car would be charging dangerously fast at the end, harming the battery and potentially leading to unnecessarily premature battery warranty claims. Also if the battery we're bottom limited, then 90% of the full 75-kWh pack is 7.5 kWh less than the 60-kWh limit. That means you should only be charging to 87.5% daily if you are to charge to 90% or less. But the car shows the daily charging window up to 90% of the 70-kWh limit. Again, I find it unlikely that Tesla would provide guidance that is known to decrease battery life. The only sensible conclusion is that the packs are top limited.
 

joeytree

Member
Jul 13, 2016
13
8
New Jersey
Even easier, run a 60 most of the way empty then unlock it. If the charge % goes up it's bottom limited.
Even easier, charge to full before a long trip and unlock. If your charge stays the same, then it's bottom limited. If it goes down to 80% then it's top limited. Anything else is a combination of the two.

As for the combination situation, 90% of 75 kWh is 67.5 kWh. And 90% of 60 kWh is 54 kWh. So you could limit the battery on both ends so that the two 90% points are the same in terms of the total pack. This would make a full charge 73.5 kWh, or 98% of the full pack. But this wouldn't make sense with the wattage at which the car charges at a SpC station when approaching "100%".
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
Speculate all you like, but the voltages don't lie. We'll know soon enough! I've got a few volunteers for data collection.

There is no "18 mile reserve" in a Tesla. There is a variable amount depending on how balanced your pack is and how calibrated your coulomb counter is. The car tries to estimate it accurately, but it will always err on the side of pessimism. This means it will give you power at least down to 0%, but any more than that is a bonus, and you can't count on it. You also don't really want to take it that low if you can avoid it.
 

emir-t

Member
Oct 28, 2013
452
553
Istanbul
Speculate all you like, but the voltages don't lie. We'll know soon enough! I've got a few volunteers for data collection.

There is no "18 mile reserve" in a Tesla. There is a variable amount depending on how balanced your pack is and how calibrated your coulomb counter is. The car tries to estimate it accurately, but it will always err on the side of pessimism. This means it will give you power at least down to 0%, but any more than that is a bonus, and you can't count on it. You also don't really want to take it that low if you can avoid it.

Ingeneer, please read my long post on the previous page. I want to know what you think about it.

In a nutshell I think Tesla is applying a higher overall C rate for the 60's supercharging and getting the cell voltage up to 4.2V quickly but that doesn't mean a 100% charge. They just stop charging as soon as they come to CV part of charging. If the intent was to charge to real 100% this wouldn't make sense as CV charging would take longer and nothing overall would change. But they don't care they only want 80%

So I think it is safe to charge to 100% AC daily but not so much at the superchargers.
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
What causes the degradation at high SOC's is the cell voltage. If we find out that the resting voltage at 100% on a 60 (not the supercharging voltage), is 4.2v then we know it's effectively at a high enough SOC to cause degradation. 90% on a new 75 is just under 4.1v. Fact. All we have to do is see what the 60's voltages are, no more speculation needed.
 

Master One

Member
Jun 19, 2016
69
32
Linz, Austria, Europe
What causes the degradation at high SOC's is the cell voltage. If we find out that the resting voltage at 100% on a 60 (not the supercharging voltage), is 4.2v then we know it's effectively at a high enough SOC to cause degradation. 90% on a new 75 is just under 4.1v. Fact. All we have to do is see what the 60's voltages are, no more speculation needed.
We don't have our new S 60 yet. What's needed and how to find out these voltages?
 

JRP3

Hyperactive Member
Aug 20, 2007
20,674
49,820
Central New York
What causes the degradation at high SOC's is the cell voltage. If we find out that the resting voltage at 100% on a 60 (not the supercharging voltage), is 4.2v then we know it's effectively at a high enough SOC to cause degradation. 90% on a new 75 is just under 4.1v. Fact. All we have to do is see what the 60's voltages are, no more speculation needed.

Can't someone just do a 100% charge using the AC charger and read the finishing voltage and current? That would show the taper, and the final voltage would be closer to resting voltage if they allow a full low current taper.
 

emir-t

Member
Oct 28, 2013
452
553
Istanbul
Can't someone just do a 100% charge using the AC charger and read the finishing voltage and current? That would show the taper, and the final voltage would be closer to resting voltage if they allow a full low current taper.

They can't, not using the charging interface at least. When you AC charge you get the voltage and amp rating of wherever you plugged in, 110V, 240V etc.

Charger transforms that into whatever the battery wants in DC and pumps into battery. So those voltage readings mean nothing. Supercharging bypasses the charger and puts in DC at whatever the battery wants so the interface reading is accurate.

We need someone to get BMS data from their AC charge. There are some apps that show it I guess but I don't know how it is done as a no Tesla owner.

My money is on 100% AC charge not reaching 4.2V per cell. As I've explained, Tesla is using higher c rates and putting in more current in the CC stage and they don't care about the otherwise would take longer CV stage because that other 20% of the battery doesn't exist in 60D.

So a 75D supercharging would either have lower relative current(earlier taper) than a 60D supercharging and reach max voltage ~90% or reach max voltage of 354 right at 80% and have same amperage. (Same taper curve)

60D just skips CV stage of charging and because of that luxury it makes CC stage faster. Easy.
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
If anyone is in the SF Bay Area with a new 60, I can easily give you access to the data. (and more) If you are not in the area, but can set up a Linux laptop or Raspberry Pi (or similar), I can work with you remotely, just not as easy. I'd prefer to have someone local. I'll give you access to the internal data for free in exchange for us sharing the battery data with the community. Drop me a PM if interested.
 
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Jlwine

Member
Jun 21, 2016
159
188
Indianapolis
As an 60D owner for six weeks now I am surprised this is still being discussed.
Multiple Tesla employees whose names I will not mention for obvious reasons, from both sales and service department have told me the exact same thing. Tesla's official word is "to just charge to what you need" they will not officially say one way or another. However, they all also said "off the record" charging the 60D to 100% is the same as charging the 75D to 80%, therefore there is no harm in doing such.
Additionally, when I am charged to 100% I do not experience any reduced regen--which I rely on heavily--rarely use the break peddle.
Finally, my three visits to SC's have all been similar, in that there is not a dramatic drop off in charging rate in the final 10-15% as would otherwise be expected.
For those who are interested in continuing to explore this from an academic perspective just for entertainment sake, I guess I understand. But in my experience and in my humble opinion there is no doubt--thus I charge to 100% ever time I charge.
 

RogerHScott

Active Member
Mar 2, 2016
1,893
1,926
Lafayette, IN
Additionally, when I am charged to 100% I do not experience any reduced regen--which I rely on heavily--rarely use the break peddle.
I asked this question before and no one answered, so maybe you can this time: what happens to your SoC when you start at 100%
and regen? Does it go to something greater than 100, or just plateau there? If you didn't live where you do ;) I'd suggest you could
try rolling down a hill starting at or near 100% and see what happens.
 

Master One

Member
Jun 19, 2016
69
32
Linz, Austria, Europe
Additionally, when I am charged to 100% I do not experience any reduced regen--which I rely on heavily--rarely use the break peddle.
That's something very important, that I have asked before as well without conclusion.

So it really is true, that full regen is available when the new 60 is charged to 100%? Did you check that also with the energy display in the dash?

That would totally make sense, with regular charging and charging from regenerative braking being two separate logics, and the software limitation only applied to the regular charging logic.

This will be very interesting to experience first hand, because we have to go downhill for about 1 km each time we leave the house.
 

emir-t

Member
Oct 28, 2013
452
553
Istanbul
I think at this point there's sufficient evidence to conclude 60 is indeed top limited and can be charged to 100% daily with no worries. However Supercharging to 100% is not the same story, it's the same as Supercharging another Tesla pack to 100%.

Only clue against it being top limited is the 354V Supercharging voltage (4.2V per cell) and I've explained how that is possible with the later taper and higher C rates (current)

Let's look at the data from a 60 to be sure anyway, it will only approve what we found out.
 

JRP3

Hyperactive Member
Aug 20, 2007
20,674
49,820
Central New York
As an 60D owner for six weeks now I am surprised this is still being discussed.
Multiple Tesla employees whose names I will not mention for obvious reasons, from both sales and service department have told me the exact same thing.

And it's quite likely this is correct, but we've also seen many examples of multiple Tesla employees being quite wrong, hence the discussion. We need solid data before we come to a concrete conclusion.
 
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S4WRXTTCS

Well-Known Member
May 3, 2015
5,727
6,877
Snohomish, WA
No Tesla keeps a portion of the bottom of the SOC off-limits as an anti-bricking buffer. I think we have heard it is around 5 kWh. The difference is that the Tesla batteries are bigger so you don't notice 5 kWh being unavailable as much.

They were referring to the top end, and not the bottom end. They were referring to what they felt was different in the Tesla versus the other EV's.

The funny thing is they asked to be corrected, but you didn't correct them. Instead you talked about something they didn't even mention.
 

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