Harris Ranch is getting first battery swap station

[RDoc]

It still seems to me that the batteries could just have an wear or degradation index saved with them or uploaded by the car to a central database. It would be based on whatever factors impact the batteries' lives and be constantly updated by the car. That would determine the pack's exchange value absent externalities such as running over trailer hitches, battery fires, etc.

There could be lots of operational/marketing models, but I'd imagine that normally people would swap for nearly the same value battery, but perhaps they could request a higher valued battery and pay the difference. Possibly, to join battery swapping, you'd register a credit card to start a running account with credits and debits depending on your swaps. Then, every 12 months or so, you'd settle up the account and continue.

Given accurate instrumentation and a centralized data base, none of this sounds very hard.

 

[jerry33]

It still seems to me that the batteries could just have an wear or degradation index saved with them or uploaded by the car to a central database.

This is the fly in the ointment. Battery degradation is very hard to measure without causing extra wear on the battery. They would only have to get the index wrong a couple of times for the public to stop trusting, so they would have to test often--which would increase the cost of the program.

 

[RDoc]

This is the fly in the ointment. Battery degradation is very hard to measure without causing extra wear on the battery.

Source?

 

[johnnyS]

I wonder how much it will cost to trade my "A" battery for the latest model.

 

[stopcrazypp]

Source?

The standard way to check the capacity (and thus degradation) is to do a complete cycle (complete charge and discharge cycle), which obviously adds extra wear.

Even if you have a constantly updating degradation/capacity index, at the very least you need a recent charge to full to be able to get a good idea of capacity (and likely a discharge near empty too). The pack also naturally drifts out of balance (which results in a much lower indicated pack capacity), something that has been discussed heavily in many threads here.

 

[RDoc]

Interesting, this prompted me to look into how remaining capacity in large Li ion batteries actually is measured. Obviously it isn't practical to do a complete charge/discharge cycle on large batteries on a regular basis, so there's been a lot of research into how to get a real time measurement of capacity. The methods seem to be accurate to about 5% which is certainly good enough considering the wide variation in actual range depending on the individual trip.

It sounds like the way to get the capacity remaining isn't so much to measure the conditions of the charge/discharge cycles, but rather to look at how the battery is behaving when subjected to loads and charging. Bottom line though seems to be that it's quite reasonable to get the current capacity of a battery without degrading it significantly.

From GM This uses data from the normal driving discharge / charge operations to provide data for a battery model. It seems to be accurate to about 5%.

Volvo supported thesis This compares a model to test measurements with similar results, less than 5% error.

 

[stopcrazypp]

Interesting, this prompted me to look into how remaining capacity in large Li ion batteries actually is measured. Obviously it isn't practical to do a complete charge/discharge cycle on large batteries on a regular basis, so there's been a lot of research into how to get a real time measurement of capacity. The methods seem to be accurate to about 5% which is certainly good enough considering the wide variation in actual range depending on the individual trip.

The slide by GM is actually quite good. It points out the difference of measuring SOC vs SOH (State of health). What we want is SOH (which is absolute capacity in kWh). Page 18 mentions the conventional method of measuring capacity (full charge/discharge) that I mentioned. The two proposed alternative methods by GM (Driving and PIC mode estimations) require a open circuit Voltage measurement (Voc) and looking up the SOC in a table before plugging it in to their equation. If you see page 20, you can see the Voc is almost flat vs the SOC near the middle. This is where the error rate tends to be high (page 5 of the Volvo link also mentions this; I'm referring to the numbered page on the corner, not the PDF document page number).

So if a consumer tends to charge near the middle, the estimate given by the pack may not be accurate, and the swap station may have to do additional charging near full or discharging near empty in order to get a better estimate. This is what I am talking about and I think jerry means the same. Unfortunately the GM slide doesn't mention what SOC window in their plot of estimated vs measured capacity (pg 26), so it's hard to tell how accurate their method will be for various SOC windows.

Also if the consumer's battery is out of balance, the swap station will have to balance it to get an accurate pack capacity estimation.

The Volvo link is less relevant. It measures SOC but not SOH (and doesn't deal with aging at all). And even though their graph says up to 7% max error (5% mean error) rate on page 30/31, on the first test on page 28 had 18% error, and second on page 29 had 21% error.

 

[strider]

So.... could we keep this thread confined to news/updates about the upcoming station and not treatises on the economics of swapping and measuring pack capacity? There are lots of threads on those exact topics already.

 

[FredTMC]

I hope we can get more confirmation of the Harris ranch rumor from a different source. I wonder when tesla will make an official announcement? I can't imagine they'd wait until it's operational.

 

[ken830]

I hope we can get more confirmation of the Harris ranch rumor from a different source. I wonder when tesla will make an official announcement? I can't imagine they'd wait until it's operational.

That's exactly what they did with the SuperChargers.

 

[apacheguy]

Anyone heard anything about this? I was really getting my hopes up. I'd be a huge let down if it weren't true.

 

[jerry33]

Anyone heard anything about this? I was really getting my hopes up. I'd be a huge let down if it weren't true.

Recall how long it took for the first Supercharger to be active. Waiting is always the hardest part.

 

[Lump]

Update?
Tesla Provides Update On Battery Swapping Status

 

[MikeC]

Seems like they may have just gotten the info about Harris from this thread, because it never confirms that TM said it. And I don't know why they would theorize that it would be for "Model S taxis" - Harris Ranch is not exactly a dense metro area requiring a fleet of Tesla taxis.

 

[markb1]

Seems like they may have just gotten the info about Harris from this thread, because it never confirms that TM said it. And I don't know why they would theorize that it would be for "Model S taxis" - Harris Ranch is not exactly a dense metro area requiring a fleet of Tesla taxis.

Yeah, they seem to present it as speculation, and they actually link back to this thread. And I agree, Harris Ranch doesn't make sense for taxis.

 

[apacheguy]

I think you guys are missing the point. While O'Connell does not explicitly define Harris Ranch as the location they have chosen, he does seem to confirm that a super swapper is in the pipeline. That's really all that I care about.

 

[palmer_md]

I drove through Harris ranch today and took a quick peek at the car wash. It was an empty building. It does not look like it had any car was equipment in some time. No signs of anyone preparing to use the space for anything. No construction signs of any kind. The original supercharger pedistal is still there next to the gas station restrooms but no cable. Not sure if it was vandalized or just decommissioned by tesla since the others became operational. It's the first time I've looked at it in a while. I did see my first model s with the aero wheels today charging. They look much different in person than in pictures. Not a huge fan but if they add freeway range as promised I'd consider them.

 

[FredTMC]

Any more news about this? Swapping... At Harris ranch or in general...

 

[apacheguy]

+1. Was hoping by year's end. Anything?

 

[Lump]

Back in June it sounded like the deal was just finalized but permitting, engineering & construction would take some time considering this one was the first of its kind, he guessed by year end we might se some construction but don't hold your breath.