S40 Max range change with SW 6.2 (2.4.239)?

[tom66]

If an S40 gets traded in for a newer model, I wonder if Tesla CPOs it as an S60 with Supercharging. I guess the only way to tell would be to check the VINs of S60s in the CPO page.

They do. People who have traded in S40s have confirmed that a 60+SC with the same VIN and features is advertised on the CPO site.

 

[dragyoul]

That's not possible... The day when it became publically known (which include by store employees) that the S40 would be carrying a 60kWh battery, was simultaneously the end of the 40 line. Nobody who ordered a 40 placed that order with the knowledge that they'd be getting a 60 instead.

I did not say that I ordered it after I learned this. My reservation was placed 12 months before. When I learned I would get an heavier battery with the same capacity, I was not happy about it and I called customer service. This is when they told me about REDUCED degradation.

At that low a SOC the algorithm drifts quite a bit and it requires a 100% charge (on all cars) to reset it so that the car knows how much capacity the battery has. (There may or may also not be balancing taking place at the end of the range).

If the actual "degradation" comes from some drifting, some S40 owners would see an increase of range and some would see a decrease. Nobody reported an increase for now ...

Without that, the car effectively has to guess how much capacity the batteries has available. It does this by keeping track of charges & voltage, but it can only be so accurate. Imagine filling a cup 66% of the way full of water every day and draining some of it again. Every day some unknown amount of dirt accumulates and stays in the bottom of the cup. You can measure how much water you're letting in and letting out, and you can weigh the cup, but you can't measure how much dirt has accumulated. How accurate will you be in hitting that 66% mark after 2 years? Not very. HOWEVER, if I allow you to fill the cup all the way and drain it once - voila, you immediately know where the 66% mark is now and you can start filling / draining it correctly again until the dirt factor becomes significant again.

Not sure about this. If you charge a lithium battery from 3.1 to 3.8 Volt (approx 50% of the capacity), I think you can compute a very nice projection of the actual capacity.

I think Tesla should allow each 40 owner to do a 100% charge once a year, or do this at a service center overnight during the annual service.

You're right. This opportunity should be given to S40 owners.

 

[deonb]

If the actual "degradation" comes from some drifting, some S40 owners would see an increase of range and some would see a decrease. Nobody reported an increase for now ...

Nobody sees upward adjustments on 60's or 85's either. I think the Model S algorithm only does downward adjustment until you range charge.

Not sure about this. If you charge a lithium battery from 3.1 to 3.8 Volt (approx 50% of the capacity), I think you can compute a very nice projection of the actual capacity.

The voltage and capacity curves in charge/discharge cycles aren't perfectly parallel. So a degraded battery will have a different voltage indicating 50% than a non-degraded battery. Tesla does a great job of guessing it, based on averaging over the fleet & battery age. But it can never know exactly what the full capacity of an individual battery is without testing it. Each time you charge your battery it will be at a slightly different current, voltage, power quality, temperature etc. than the person next to you.


Why on earth for the S40 Tesla didn't just go and say "let's always charge to 140 miles of range" however, is beyond me. I guess they didn't want to invest in different software for the S40 and S60. But now you get an S60 that is charged every day to 66%, and even a S60 isn't terribly fond of that.

 

[Longhorn92]

So, on my S40, I switched the display to remaining battery % instead of rated miles at the beginning of the year (I believe when we got v6.1). So, I am unsure if my max charge rated miles dropped with the latest software version, but it still charges to the same max percentage (67 or 68%), so I have noticed no decrease in the percentage charge with any of the newer software upgrades.

 

[wk057]

Does anyone know what SoC window the S40 operates within? I'm curious as to if it actually uses 0 to 66% or 33% to 100% or 23% to 90% or so. I would think a SoC range in the middle like 16% to 84% would probably be best for least degradation.

 

[Longhorn92]

Does anyone know what SoC window the S40 operates within? I'm curious as to if it actually uses 0 to 66% or 33% to 100% or 23% to 90% or so. I would think a SoC range in the middle like 16% to 84% would probably be best for least degradation.

It's my understanding that it is 0% to 66% (67 or 68% in reality). That is, my battery pack would be out of juice if I went to 0% (plus the normal additional reserve). I think they took the easy way on the software side and just limited the "Set Charge Limit" slider to a max of 68%.

 

[brucet999]

As a somewhat random thought, I would be kind of mad if I ran out of power in a 40 knowing there is 20 kWh sitting there that I couldn't use...

I wonder if Tesla roadside assist could simply bypass the limiting firmware in such a case.

 

[wk057]

It's my understanding that it is 0% to 66% (67 or 68% in reality). That is, my battery pack would be out of juice if I went to 0% (plus the normal additional reserve). I think they took the easy way on the software side and just limited the "Set Charge Limit" slider to a max of 68%.

I'd actually be quite surprised if this is the case. It wouldn't make much sense to drain the battery so low with all of that locked up buffer. Anyone ever get an HV reads of a 40 at a known SoC? Peek at the diag screen with voltages for the same?

 

[Longhorn92]

I'd actually be quite surprised if this is the case. It wouldn't make much sense to drain the battery so low with all of that locked up buffer. Anyone ever get an HV reads of a 40 at a known SoC? Peek at the diag screen with voltages for the same?

I don't think they put much thought into it since it was less than 400 cars. The flip side is that full charge for us S40 owners is a great state for the battery. I almost never have less than 20% when I plug in, so the batteries usually stay between 20-66% charged.

I would be happy to perform some measurements, but I'm not sure I know how.

 

[dragyoul]

I'd actually be quite surprised if this is the case. It wouldn't make much sense to drain the battery so low with all of that locked up buffer. Anyone ever get an HV reads of a 40 at a known SoC? Peek at the diag screen with voltages for the same?

I really feel like Tesla made it really simple and limited the charge to 68%. Since the margin is low for the S40, I guess they did not invest a lot of engineering time on the battery re-programming. If the cells normally charge from 3.0 to 4.1V (as an example) and the algorithm for capacity calculation is based on this, it's much easier to allow a charge from 3.0 to 3.8V instead of 3.2 to 4.0V ... At least, I am pretty sure they did not make long-term testing on a battery that would charge between 3.2 and 4.0V, so it's kind of tricky to implement this on a new car ...

I wish they did a 16 to 84% implementation on the car, but I have no evidence of this. Supercharging voltage would have been useful, but since it not allowed, I have no hint about voltage VS SoC. Maybe this forum has some snapshot of the battery diagnostic tool of a fully charged S40. Would be very useful!

 

[deonb]

I'd actually be quite surprised if this is the case. It wouldn't make much sense to drain the battery so low with all of that locked up buffer. Anyone ever get an HV reads of a 40 at a known SoC? Peek at the diag screen with voltages for the same?

If you see the screenshots of the implementation - it really does look like a 60 in all ways, just that you can't move the slider past the 68% mark.

I think the engineering between the 40 and 60 basically boils down to 2 lines of code.

if (model() == S40 && sliderValue > 68)
sliderValue == 68;

 

[Papafox]

Interestingly, I saw my range creep back up to 133 miles today, a couple days after loading the latest software update.

 

[Fiver]

If you have a S40, it might be worth a phone call or email to Tesla to ask them what the trade in value is on it. You might be able to upgrade to a CPO 85 nicely optioned for less then $10k cost of unlocking your pack.

 

[wk057]

If you have a S40, it might be worth a phone call or email to Tesla to ask them what the trade in value is on it. You might be able to upgrade to a CPO 85 nicely optioned for less then $10k cost of unlocking your pack.

I'm pretty sure Tesla would factor that in, buy back at some lower price and resell as a 60.