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Comment by thrownaway2424 | Hacker News Reader

I don't get this article. The battery in a Tesla Model S is literally a huge array of Panasonic flashlight batteries. It is an off-the-shelf catalog item you can order from Panasonic. Admittedly, you should probably have prior arrangements before ordering millions.

The central insight of the Tesla founders was that people really will pay $85000 for an electric car. The other auto makers didn't believe that.

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> The battery in a Tesla Model S is literally a huge array of Panasonic flashlight batteries. It is an off-the-shelf catalog item you can order from Panasonic.

Um, no. Viewing the battery of a Tesla Model S as just a big flashlight battery misses the whole point of what Tesla is doing.

A flashlight battery does one thing: it discharges energy until it's empty. Even an ordinary rechargeable household battery only does two things: it recharges, and then it discharges.

The battery in a Tesla Model S, OTOH, is continuously computing whether to charge or discharge, how much to charge or discharge, what its current state of charge is, how to manage charging and discharging to maximize its life, etc. And it has to do this in a constantly changing environment--a car that is traveling at varying speeds over varying types of roads. (Doing it for a home battery is actually easier, in a way, because there is less variability in the load.)

This sort of technology is absolutely critical if batteries are going to become significant in our energy budget on a large scale. The energy storage medium of the battery is only a tiny piece of the whole picture.

> The battery in a Tesla Model S, OTOH, is continuously computing whether to charge or discharge

Is it? I would imagine the software does that. The battery really is a large array of commodity batteries made by panosonic. Tesla is doing the gigafactory for vertical integration and to bolster it's own supply. Obviously, they have done a lot of innovation around the pack in terms of heat distribution and cell construction, as well as the management system. The innovation is really about the macro-cell construction and the software to manage the array. On a micro-level it is just a bunch of commodity batteries wites into small cells, that make up a large cell array.

> I would imagine the software does that.

Obviously the lithium-ion cells themselves aren't doing the computation; software is. But the software should be considered part of the "battery" as a system. Without the software the lithium-ion cells are useless for this application, and indeed for any application more dynamic than a flashlight. So the software development that Tesla has done is essential for making batteries viable in the sorts of applications that people want to use them for to help solve our energy problems.

would "realtime battery management software company" be a better fit?

Possibly, but as I understand it, the software is tightly coupled to the battery hardware; if you were to swap in a different kind of cell, or even the same kind of cell but from a different manufacturer, you would have to rework much of the software. That's why I think it's better to view the storage cells and the software as a single integrated "battery" system.

> Is it? I would imagine the software does that.

It is. JB Straubel (Tesla's CTO) has done all of the hard work with regards to their energy management system.

Sure, babying the pack with a liquid medium for thermal transfer helps (compared to the inferior air cooling on the Nissan Leaf battery pack), but the foundation for both the performance and longevity of the Roadster and the Model S battery packs is Straubel's remarkable work.

The cells themselves are COTS Panasonic NCR18650A without built-in protection circuits.. The management circuits are probably developed by Tesla but are external to the batteries, most likely a circuit per array of parallel cells.

Having a protection circuit per cell would be wasteful and also result in quite a bit of power loss and complexity in wiring them up.

I toured the Tesla factory in Fremont, CA last Monday. During the completely awesome 1 hour tour, our guide answered many detailed questions about their cars and manufacturing processes, including how Tesla instruments battery cells.

We were told that they instrument every single one of the 7,000+ cells for temperature and voltage.

That's an overstatement. They do not have 7000+ temperature and voltage sensors per pack.

Each of the 16 modules is split into 6 blocks where the 70+ cells within a block are all wired in parallel -- so they are going to have the same voltage. The blocks within a module are wired serially and the modules are also wired serially.

Each module has a battery monitoring chip:

http://www.ti.com/product/bq76pl536a

It has seven voltage measurement inputs (between each block and before/after the outer blocks) so it can tell the voltage of each block. It can also control a bleed resistor per block (for balancing). There are two temperature sensors per module.

Each module also has an 8051 (C8051F530A) that talks to the battery monitoring chip and to the data network connecting the modules to the "global" battery management system which has a Altera CPLD and (probably) an ARM CPU.

http://www.teslamotorsclub.com/showthread.php/34934-Pics-Inf...

Thanks for clarification and link to the teardown pix. Very interesting.

They aren't really COTS. They were for the Roadster, but for the Model S they use a specialized chemistry as well as removing the protection circuit.

[Source](https://www.youtube.com/watch?feature=player_detailpage&v=9c...)

That's standard for NCR18650A cells though - they ship with no protection circuit and I believe the same chemistry that the Model S is using. The protection circuits are added by companies that buy raw cells from Panasonic.

Charge balancing is a common feature, often built in to charge controller ICs. Of course Tesla has to do this on a much larger scale, like with all of its power electronics. But so does a Prius.

I'm not sure how much of a technological lead Tesla has versus major car companies already producing hybrids and electrics, but it can't be that huge, and those guys have way bigger R&D budgets.

The cells used in Tesla's battery pack are a standard form factor, but they are not standard off-the-shelf parts. If you read up on the battery pack you'll find that it uses 18650 cells, and you'll find that you can buy commodity 18650 cells from all sorts of places. But 18650 is just the shape, not the contents. Tesla's 18650s do come from Panasonic, but they're not off-the-shelf items. They have a custom chemistry and they also don't include the standard battery protection circuits found in almost all such batteries (because Tesla provides that circuitry externally).

Sure. Similarly Google is just a bunch of commodity off-the-shelf hard drives.

If some talking head wrote a blog called "Google is a hard drive company" that would be a worthy retort.

Joking aside, one could probably write that article and make a good case based on the same logic.

They are very good at building cheap servers, and running them cheaply.

You say electric car like it's some souped up Prius (I own a Prius).

The Tesla Model-S is an amazing vehicle that's not only electric but amazing to look at and drive.

As an aspirational status symbol it's got a hell of a lot of cachet 3 years after it's introduction. That's a feat of product marketing and engineering.

Absolutely an achievement of marketing worthy of the best marketeers in history. But the article is wrong on it's face when it states "the Battery Tech they Developed While Building EVs" because Tesla has not developed any battery technology of any kind, ever.

And there's some deal with Panasonic for the Gigafactory as well — it sounds very much like it'll be manufacturing stuff that's basically Panasonic IP to start with.

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