P85D Power draw numbers do not add up...

[kennybobby]

Tesla cell-level fuse bondwire material?

Aluminum
0.28 mm diameter
8 mm length

 

[Zetopan]

It was Elon Musk during some Q&A call if I recall correctly. Might even have been the "Three Dog Day" call. Not sure, but I did hear the claim that around 90% SoC was optimal.

The only verification that I have found for the 90% number had nothing to do with the battery resistance. Elon has stated that the regenerative braking had the best response when the batteries were not charged to more than 90%. Since the regenerative braking tries to charge the battery and a fully charged battery cannot accept any more charge, the regenerative braking can't really function and the non-regenerative (conventional friction) braking must be used under those conditions instead. None of that has anything to do with the battery internal series resistance being lowest at a 90% charge. Hence, it is unsurprising that you have not found any correlation with the "a 90% charge exhibits the lowest battery resistance" claim in your testing.

 

[MuppetOwl]

Best performance at 90% is the answer from Tesla on the 691 hp issue.

Hi Ken,
I work in Elon Musk’s executive office at Tesla. Elon received your email and wrote the following reply, which he asked me to share with you.

There is a software update in V 7.0 (only for performance versions of the Model S) that allows the driver to command the battery to the optimal temperature and charge state for maximum power. Normally, the battery is optimizing for range and long life, so 0 to 100 kmh acceleration can be affected by 0.2 seconds or more if too cold, too hot or at the wrong charge state. Occasionally pressing max performance will not have a noticeable negative effect on battery life, but it should not stay there all the time. It is important to note that being at 100% state of charge does not deliver the best acceleration -- lowest impedance is at ~90% SoC.

I do want to emphasize that there has not been any reduction in insane mode performance for customers from the benchmark vehicle used by Motor Trend to establish the 0 to 60 mph (96.6 kph) in 3.1 sec. This was achieved at the 1300 Amp level, with no upgrade to the fuse, contactor or battery spine. However, they used a base vehicle and medium weight driver. Larger occupant weight and adding options that increase weight will reduce the acceleration. Also, the Motor Trend standard excludes the first 28 cm of rollout. Including this rollout adds approximately 0.2 seconds to the acceleration.

One final note is that, while gasoline cars get worse with altitude, electric cars actually get faster. All cars experience reduced air resistance, but gasoline cars become increasingly oxygen-deprived the higher they go. The Motor Trend test was done at approximately sea level, so the Model S will outperform a combustion car of the same nominal acceleration as altitude increases.

All the best,
Sam

Email Elon | P85D Owners Missing Performance

 

[JRP3]

lowest impedance is at ~90% SoC.

I would love to know the physics supporting this claim.

 

[kennybobby]

AC/DC

AC testing at 1kHz gives cell impedance, which is a different value from the DC load test measurement of resistance.

Two different test methods give different results yet both are correct. From battery university,

Smaller batteries often use the popular 1000-hertz (Hz) ohm test method. A 1000Hz signal excites the battery, and the Ohm’s law calculates the resistance. It is important to note that the AC method shows different values to the DC load, and both readings are correct. For example, Li-ion in an 18650 cell produces about 36mOhm with a 1000Hz AC signal and roughly 110mOhm with a DC load. Since both readings are correct, and yet they are so far apart, the user needs to consider the application.

The pulse DC load method provides valuable readings for a DC application such as driving a motor or powering a light, while the 1000Hz method better reflects the performance requirements of a digital load, such as portable computing and mobile phones that rely to a large extent on the capacitive characteristics of a battery. Most resistance values indicate the test method used.

The Physics:
When a cell is 100% full it won't accept the positive-going half of the 1kHz sinewave as well as if it is partially discharged (e.g. 90%), which allows current flow in both directions.

 

[JRP3]

But does that have any real world relevance to DC current flow?

 

[kennybobby]

The Winning Guess...

Congratulations to Jason for being the first whiz-kid (wk057) on the block to identify the 691hp issue, report it, and stand up to abuse to the point of banishment to defend his position without caving. We should all send him a prize of sorts, but he already has more toys than anybody else...LOL!

 

[lolachampcar]

Second but I'm afraid I'm going to have to see that toy list before I sign up for the second half of that statement

 

[Zybane]

Anyone else notice the Ludicrous HP is now listed as a maximum of 532 HP due to battery constraints on the Tesla web site?

 

[Canuck]

Congratulations to Jason for being the first whiz-kid (wk057) on the block to identify the 691hp issue, report it, and stand up to abuse to the point of banishment to defend his position without caving. We should all send him a prize of sorts, but he already has more toys than anybody else...LOL!

I read the posts where he was banned and it had nothing to do with him identifying "the 691hp issue, report it, and stand up to abuse". It had to do with him being extremely rude and condescending thus breaking forum rules.

 

[wk057]

I read the posts where he was banned and it had nothing to do with him identifying "the 691hp issue, report it, and stand up to abuse". It had to do with him being extremely rude and condescending thus breaking forum rules.

You realize this is completely off-topic here, right? I'm getting pretty tired of your repeated accusations and slander on this topic (and others where you feel the need to single me out for one reason or another). You were not a party to any of the conversations that resulted in my ban, nor were all of the conversations involved publicly presented and preserved.

So, respectfully, just stop and mind your own business.

 

[Canuck]

You realize this is completely off-topic here, right? I'm getting pretty tired of your repeated accusations and slander on this topic (and others where you feel the need to single me out for one reason or another). You were not a party to any of the conversations that resulted in my ban, nor were all of the conversations involved publicly presented and preserved.

So, respectfully, just stop and mind your own business.

I posted in response to kennybobby who said "(wk057) on the block to identify the 691hp issue, report it, and stand up to abuse to the point of banishment." That was not a correct statement and I corrected it. Nothing I have said is slanderous although you probably meant libelous since slander is spoken and libel is written. In any event, it's a public forum so I will not be minding my own business. But I will always post the truth, as I see it, and in a respectful manner. Sorry if that offends you.

 

[llavalle]

Congratulations to Jason for being the first whiz-kid (wk057) on the block to identify the 691hp issue, report it, and stand up to abuse to the point of banishment to defend his position without caving. We should all send him a prize of sorts, but he already has more toys than anybody else...LOL!

Hats off to you wk057.

 

[wk057]

Canuck has now been successfully added to your ignore list.

This is most certainly the only viable option since derailing topics by attacking people doesn't seem to matter around here much. There's no value in it whatsoever and it contributes nothing useful to the conversation.