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

Electroman

Supporting Member
Supporting Member
Aug 18, 2012
6,395
7,532
TX
I have see 50kw right up to 100% before also.


Well.. well. Then how can that be true 100%. Ingineer had to explain this before he can say with certainty that it is bottom limited.

50kw near 99% means it is not true 100%.

Although now I am wondering if the kW rate we see on the screen is a running average just like mph value
 

jelloslug

Active Member
Jul 21, 2015
4,728
6,405
Greenville, SC
Well.. well. Then how can that be true 100%. Ingineer had to explain this before he can say with certainty that it is bottom limited.

50kw near 99% means it is not true 100%.

Although now I am wondering if the kW rate we see on the screen is a running average just like mph value
Well, you have the amps and the volts right there on the other side....
 

chris5639

Member
Jul 8, 2016
149
145
San Diego, CA
That would be a big disappointment if it's bottom limited. I really like the idea of having full range without degrading the battery as much as a full charge would. I'll call and ask them about it.

I have a new 60D and recently completed a road trip in Texas from Dallas to Galveston utilizing the Corsicana, Huntsville and Houston superchargers. In almost all cases I range charged to 100%. The charge rate never tapered off and again, in almost all cases the car waited for me rather than the other way around. I was telling my wife that it almost charged too fast. Like others, this leads me to believe the 60 is software limited at the top end and not the bottom end. What would be the alternate explanation? That due to a software bug, the superchargers are charging at an unsafe rate for all new 60's that have the 75 kWh batteries? Wouldn't we have overheated batteries in that case? At times when I returned to the car right after it finished charging (I HATE taking up a space), I did not hear the battery management system cooling the battery. Perhaps I missed it but I usually can hear it.
 

⚡️ELECTROMAN⚡️

SS of 96 and falling
Jul 15, 2016
2,872
5,443
Pacific Northwest
I called the service number on the website. It took ten minutes of trying to explain my question and what made the question significant. The conclusion was, that the guy I talked to, had no idea if the battery pack was 80% charged or 100% charge when the 60 kWh car's screen said 100%. Should I call and ask sales? I'm guessing they would be even more clueless, if that is possible. So, is anyone out there getting ready to pay for the upgrade to the 75 kWh?

Even easier, run a 60 most of the way empty then unlock it. If the charge % goes up it's bottom limited.
 

MikingCO

2021 MX LR+
Jun 22, 2016
138
133
Dallas, TX
I called the service number on the website. It took ten minutes of trying to explain my question and what made the question significant. The conclusion was, that the guy I talked to, had no idea if the battery pack was 80% charged or 100% charge when the 60 kWh car's screen said 100%. Should I call and ask sales? I'm guessing they would be even more clueless, if that is possible. So, is anyone out there getting ready to pay for the upgrade to the 75 kWh?
I've already volunteered my car if someone will simply volunteer the funds. I will even take time out of my schedule to get it rebadged. I'm 90% of the way to solving this puzzle. Who is going to help me the last bit?
 

⚡️ELECTROMAN⚡️

SS of 96 and falling
Jul 15, 2016
2,872
5,443
Pacific Northwest
It's very tempting to pay for your upgrade just to find out, but I'm kind of a tightwad. Maybe it's top limited now, but with the pack needing to be 100% charged a few times a year, for balancing, they might make it bottom limited with an over the air update. Maybe I should call the service center again and ask how I'm going to balance my batteries if it's not actually charging to 100%. :rolleyes:
 

chris5639

Member
Jul 8, 2016
149
145
San Diego, CA
It's very tempting to pay for your upgrade just to find out, but I'm kind of a tightwad. Maybe it's top limited now, but with the pack needing to be 100% charged a few times a year, for balancing, they might make it bottom limited with an over the air update. Maybe I should call the service center again and ask how I'm going to balance my batteries if it's not actually charging to 100%. :rolleyes:

Here's a blurb from BU-803a: Cell Matching and Balancing – Battery University

active balancing shuttles the extra charge from higher-voltage cells during discharge to those with a lower voltage. Active balancing is the preferred method for EV batteries, but it requires DC-DC converters. The corrected currents are in the mA range only. Applying a heavy load during acceleration, followed by rapid-charging with regenerative braking requires well-tuned cells in a high-voltage battery to attain the anticipated life. EV batteries in the Tesla, BMW i3 and other EVs employ active balancing to minimize cell stress.

This would suggest balancing by charging to 100% is not necessary?
 

Steveb48

Member
Aug 25, 2016
33
11
San Jose Ca
I was told by sales last weekend that you could charge a 60 to 100% without degradation of the pack and that supercharging would be faster due to the later taper.
 

emir-t

Member
Oct 28, 2013
452
553
Istanbul
OK so I'll try and comment on this confusion with the limited scientific knowledge I have and try to clean things up a bit. I've been obsessed with batteries since I got into EVs about 4 years ago and have been reading about them ever since. I'm no engineer by any means so take everything I say with a grain of salt but here goes;

I'll write my conclusion first for TL;DR: I think we need more data to tell if it is perfectly OK to charge to 100% daily, but it most defintely is. Here's why;

All the data we have so far has been from the superchargers. And superchargers have one thing in mind; charging really really fast. Also becaue lithium-ion batteries use CC-CV charging method (constant current, constant voltage) battery charging current reaching 4.2V per cell (~353V) doesn't mean the 'real' 75 pack is actually full and the pack is bottom limited. (I'll have to disagree with Ingeneer on this upon second thought)

We have to first get rid of looking at only the kW. We should be looking into amps and voltages. A CC-CV charge means the battery is applied a constant current (give or take) until it reaches max. allowed voltage of 4.2V and then it is at CV stage. At constant voltage stage the voltage stays the same and current tapers off. From 60D supercharging data we have so far we can conclude that it indeed does enter the CV stage since voltage at 100% is 354V --> 4.2V per cell.

Here's the tricky question; at what percentage does the battery switch into CV stage? Definitely not 100% because as soon as it reaches that state if you disconnect you'll see voltage going down. This is determined by the C rate of the battery. (C rate: current the battery is charging/discharging at compared to capacity, for example a 3Ah cell charging at 3 amps is 1C, same cell charging at 1.5 Amps is 0.5C)

Now this article briefly mentions the CC-CV charging and C rates used. It says; (I quote)

When charging at higher currents, the cell voltage rises more rapidly due to overvoltage in the electrode reactions and the increased voltage across the internal resistance of the cell. The constant-current stage becomes shorter, but the overall charge cycle time is not reduced because the percentage of time in the constant voltage stage increases proportionately.

So this leads me to believe - again, I might be wrong - that Tesla is comfortably using higher C rates in supercharging the 60, getting the cell voltages up very quickly and not worrying about CV stage taking long because they never have to CV charge all the way anyway. The battery is limited to 80% max charge with the limit at the top. (Tesla isn't using a strict linear CC-CV because cell amperage and voltage taper gradually per Tesla's algorithm, so I mean they can taper the current rate later on and afford that higher overall C rate)

Let's look into the new 75 pack configuration to get Amp and voltage levels, using the 3.3Ah cells all Teslas use right now;

Pack capacity; 3,3Ah cells, 74 in parallel = 244Ah.
Pack voltage: 3.7V nominal cell voltage, 84 in series (14 modules in 6 strings each) = 311V (nominal)

311*244 = 75,8kWh. (around 72kWh should be usable for the owners)

Now let's "reverse engineer", so to speak, the virtual capacity of the software limited 60 pack; (because 100% is from the virtual standpoint)

Voltage should be the same for motor and drive train usage, so 311V.

60kWh/311V = 193Ah


To support my argument I'll look at the very limited data we have. Everyone either shares their data in kW, miles added or SoC % all useless from this standpoint. We need amperage and voltage. Here's an old video of Bjorn's 85kWh pack Supercharge video. Notice the empty pack starts charging at about 1.25C (charging at 286 amps with the old 229Ah pack; 286/229) Tapers to 1C around ~45% and continues below 1C. Pack starts CV charging (404V) around 90%.

Comparing this 60D supercharging data and privater's data form this thread with Björn's we can see that at 37% virtual SoC (real 30%), 60D is charging at ~295A (1,21C) and 85kWh's 30% supercharge speed is 1.16C. Further into the charging at virtual 80% (real 64%) 60D is pulling from both reddit and privater's data average 0.77C. Whereas at that point 85 is pulling 0.64C.

So the actual comparable speed difference got from 4% faster to 20% faster, 60 didn't taper as much as 85 did. As a result 60D obviously gets to CV stage way earlier than 80%, allowing for faster supercharging. (actually from reddit data it's as if it's getting to 100% right around the beginning of CV stage)

I'm pretty sure about my theory but I need an engineer's input.

With all this in mind, AC charging is a different thing. Because they don't need speed there, the charger probably doesn't charge all the way up to 4.2V per cell. We need much more Supercharging videos and BMS, CANBUS information to be perfectly sure about this but I would think that it is OK to charge 100% daily on the new 60D, just not on the Supercharger, because upper level voltage is what hurts the battery.

All in all we need a Supercharging video of 60D vs 90D in amps and voltages. Since at the proof I provided I compared old 85kWh 3100mAh cells with new 3300Ah cells. They could've improved cell chemistry too to accept higer C rates but I don't think by that much.

I know it has been a long read but I finally feel like I figured it out, what do you think?
 

privater

2016 Model S and 2017 Model 3 owner
Jun 22, 2016
254
744
CA
I know it has been a long read but I finally feel like I figured it out, what do you think?
I think we only need a 75 kwh Model S supercharger data to compare with soft-lock 60 kwh. All myth will be debunked. My personal bet is front 0-80% is same with 60kwh 0-100%, and last 80-100% is similar to S85/90


But the truth is those 75 kwh Model S are extreme hard to find in here.
And also don't forget about this soft lock is meant to be modified from Tesla, they can lock bottom, top, or both whatever they like, whenever they like.
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?
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
I've collected detailed data logs from a refresh 75 (not locked), but not yet on a locked car.

The 75 behaves exactly like the older 70's voltage-curve wise, with the exception that the new 75 charges with higher current and way less taper. I think this may be due to 3 things; improvements to electrochemistry, thermal management, and the doubling up on the bond wires that connect each cell to the bus plates.

Until I get real data myself from a new locked 60 pack, I can't state for sure, but evidence presented from several members here indicates that the pack voltage is at 352 volts when completing a 100% supercharge. This means 4.2v/cell, which is 100% charge. Going over that is instant damage to the cell. There has been a theory proffered by some here that Tesla/Panasonic changed the electrochemistry such that is supports a higher 100% charge voltage, which is highly unlikely due to the way voltage is established in the cell. Also, if this were the case, then I'd see it on the 75 pack. Nope!

If there is anyone with a new 60 in the SF Bay Area and you'd like to participate in this experiment, please PM me. We will take detailed logs from your car and get to the bottom of this once and for all.

You absolutely cannot go on the word of a random Tesla employee. They have been proven to be wildly inaccurate with technical information time and time again. Until Tesla releases a public statement which will have been vetted by engineering, you cannot place your pack's longevity on their guesses!

For health and accuracy of the SOC information, I recommend an extended 100% charge on AC power at least 3 times a year, preferable done when the pack is cool. This means plug it in and wait until about an hour after the UMC disconnects (the green Xylon LEDs stop sequencing), before you drive the car.

What's most damaging to a pack is to charge it to 100% and let it sit there unused. This is exacerbated as the pack's temperature rises. It's also good for the pack and your range to ensure it's balanced, so this is why I recommend a 100% charge on occasion.

For daily use, only charge at most to 90%. If you can comfortably only take it to 80%, that's even better. Anything lower is not going to really be observable. Lithium packs like to be treated like people. Fed, but not too much, and kept comfortably cool. Over-eating, especially when it's hot, is not good! =)

Right now I can't provide any proof, but I'm convinced enough by the anecdotal evidence. Don't keep your pack at 4.2v/cell! You will definitely cause degradation!
 

Alketi

Member
May 3, 2016
875
2,464
U.S.
I've collected detailed data logs from a refresh 75 (not locked), but not yet on a locked car.

The 75 behaves exactly like the older 70's voltage-curve wise, with the exception that the new 75 charges with higher current and way less taper. I think this may be due to 3 things; improvements to electrochemistry, thermal management, and the doubling up on the bond wires that connect each cell to the bus plates.

Until I get real data myself from a new locked 60 pack, I can't state for sure, but evidence presented from several members here indicates that the pack voltage is at 352 volts when completing a 100% supercharge. This means 4.2v/cell, which is 100% charge. Going over that is instant damage to the cell. There has been a theory proffered by some here that Tesla/Panasonic changed the electrochemistry such that is supports a higher 100% charge voltage, which is highly unlikely due to the way voltage is established in the cell. Also, if this were the case, then I'd see it on the 75 pack. Nope!
Ingineer, Randy Carlson at Seeking Alpha is speculating that Tesla is using a new chemistry to finally exceed the 4.2V threshold for their 60/75 pack. He wrote a long post about it here: http://seekingalpha.com/article/4001134-tesla-already

He derives his theory from weight measurements of the S70 vs S60/75 vehicle, concluding that the weight difference doesn't match what one would expect by the difference in battery capacity (5kWh). It's an interesting, if not enticing theory. One confirmation, as he mentioned, would be to measure the pack voltage of a fully charged 75 and back-calculate to see if the 4.2V threshold has truly been breached. Hopefully someone may be able to do that soon. Let me know your thoughts. [Sorry for the off-topic nature of this post]
 
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Reactions: privater

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
Here's a partial data dump from a new Refresh 75 recently charged to 100%. This proves there is no new electrochemistry that allows charging over 4.2v/cell.

Code:
bms_cac_min    243
bms_contactor_state    OPEN
bms_current    -0.10A
bms_inlet_active_cool_target    52
bms_inlet_active_heat_target    8
bms_inlet_passive_target    30
bms_iso    3.58MΩ
bms_max_temp    84.2°F / 29°C
bms_min_temp    82.4°F / 28°C
bms_nominal_fullpack    73.4
bms_pack_temp    80.6°F / 27°C
bms_pack_temp_pct    44
bms_state    STANDBY
bms_values    4.185,4.185,4.185,4.185,4.185,4.185,4.185,4.185,4.184,4.184,4.183,4.184,4.185,4.185,4.185,4.185,4.184,4.183,4.185,4.184,4.184,4.185,4.184,4.184,4.184,4.184,4.183,4.183,4.183,4.184,4.185,4.185,4.185,4.186,4.185,4.185,4.184,4.182,4.183,4.183,4.183,4.185,4.183,4.183,4.185,4.183,4.183,4.185,4.185,4.185,4.185,4.185,4.185,4.185,4.182,4.182,4.182,4.182,4.183,4.184,4.185,4.185,4.185,4.185,4.186,4.184,4.185,4.185,4.185,4.185,4.186,4.185,4.185,4.185,4.185,4.185,4.185,4.184,4.185,4.185,4.185,4.185,4.185,4.185,--,--,--,--,--,--,--,--,--,--,--,--,28.43,28.43,28.55,28.54,28.45,28.52,28.45,28.69,28.48,29.05,28.27,28.70,28.04,28.60,28.19,28.02,28.09,28.56,28.36,28.75,28.23,28.37,28.36,28.55,28.20,28.23,28.09,28.16,--,--,--,--
bms_voltage    351
cfg_efficiency_package    S2
cfg_energy    Energy75
cfg_pack    80
cfg_soft_pack    0
SOC    100
SOE    100
soft_pack_energy_limit_pct    100
USOE    100
 
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Reactions: MP3Mike and Alketi

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