Tag Archives: li-ion

Apple’s Batteries, Apple Cars?

Earlier this year, a series of rumors and reports emerged that Apple may (or may not) be making serious investments in developing an electric vehicle. Taken as a whole, the rumors and reports are intriguing, if not convincing, but there are also plenty of alternative explanations for the circumstantial evidence.

This isn’t a site about Apple though, or cars, or technology in general, it is about batteries, and my purpose with this post is to note some interesting tidbits about Apple and batteries that have emerged in the attention to the Apple Car.

First, Apple has been recruiting people from battery companies. They are being sued by A123 for hiring some of their employees. A123 is a battery company specializing in Lithium Iron Phosphate (AKA LiFePO) cells. The employees in question were A123’s former CTO, Mujeeb Ijaz, and various engineers responsible for developing and testing lithium ion batteries. A123’s earliest design wins were in batteries for tool packs, but there current focus is squarely on providing batteries for the growing electrical vehicle market. They also faced bankruptcy recently, so it is not surprising that their employees were open to be recruited to working on battery technology at Apple, whether or not those batteries will be used in electric cars.

In the complaint, A123 claims that Apple has hired employees from other li-ion battery companies A123 has ties to, including SiNode Systems, Samsung, Toshiba, LG, and Panasonic.

Apple is clearly interested in advancing the state of the art for battieries in service of its publicly known product lines. The design of the upcoming Apple Watch seems strongly influenced by the issue of battery life and the new MacBook goes to extraordinary lengths to maximize the volume of the device occupied by the battery.

This isn’t anything new for Apple, but they’ve gone to extraordinary lengths with the new MacBook.  Apple used to use battery packs built around the cylindrical, metal encased, 18650 cell, but about 10 years ago, they were pioneers in the use of pouch cells, which use a plastic pouch, rather than a metal can, and are shallow rectangles, rather than cylindrical. Apple’s move to pouch cells allowed thinner systems with less space wasted in the baps between cells. The followed up by forgoing field-replaceable batteries, for battery packs installed in the main cavity of the computer. The space saved was used to increase battery capacity. The Retina Macbook Pro went even further, gluing the cells directly to the laptop case. It also used a mix of cell sizes.

The latest MacBook goes even further. The logic board is tiny compared both to past Apple laptops, and the batteries, which occupy most of the volume and floor-plan of the computer, are unprecedented. The cells aren’t simple rectangles, they have rounded and notched edges.

Screen Shot 2015-03-17 at 3.36.43 PM

For even more battery density, they are stacked in a terraced fashion.

Screen Shot 2015-03-17 at 3.36.51 PM

Whether an Apple car makes it to market, if it is being developed at all, I am certain that Apple wants to stay on the cutting edge of battery development, whether in packaging, chemistry, management or manufacturing. Whether it is Apple, or its suppliers in the lead, Apple needs people who know all about the development, manufacture, and use of lithium ion batteries. It is no surprise they’ve been hiring them.


Used Tesla 444 cell 6s74p Modules for Sale

Last night, a new member on the EEVBlog forums posted that he had  ten battery modules from a Tesla Model S for sale. The asking price? $1,900 each, shipped within the US.

According to the poster, it is a rev b pack from a car with ~4,000 miles on it. Each module has 444 18650 cells, configured as six in series, 74 in parallel (6S74P). Capacity is 233Ah and 5.3 kWh. Each module has its own Tesla BMS (battery management system), and plumbing for heating/cooling.

I also found another thread about the same modules in in a DIY electric vehicle forum. There is more discussion there, including some testing results by one of his collaborators. And here is a thread on another EV forum where the collaborator posted earlier in the month about hunting down the source pack and break down some of the modules into cells for sale.

Doing a little math, this works out to $4.28/cell, $0.12/Ah and $2.78/Wh. Back in November, I came across a Hack-a-Day interview with the first person I know of to publish a Tesla Model S pack teardown. I noted that he’d paid ~$20 for his pack, which worked out to about $3/cell, so, this is ~40% more expensive/unit, but with the advantage of 1/10th the initial outlay.

The cells in these Tesla packs are a variant of the Panasonic NCR18650 cells. The exact variant isn’t known, and is probably Tesla-specific, but there are NCR18650 cells with similar capacity on the market. Like all 18650 Li-ion batteries, any NCR18650 cells available retail, or in smaller wholesale quantities have passed through a few middle-men, making the wholesale prices hard to estimate. What I do know though is that it is hard to find such cells for less than $6.50. Laptop packs with 9 similar cells are over $100 new, though you can generally find surplus packs for $50 or $5.50/cell. With only 4,000 miles on the battery pack, and given that Tesla treats them pretty gently, the cells in these packs are going to be pretty close to new condition.

Given all this, these modules seem like a reasonable price if you can use the entire module intact.

On the other hand, using cells from these packs individually probably doesn’t make sense. In addition to the effort required to disassemble the module, these cells may need to be wrapped. It is also quite possible that these cells don’t have some of the safety features people expect with 18650 cells, since the pack has other provisions for dealing with cell shorts and overheating.

If you buy any of these modules, I’d be interested to hear about your plans for them. If you’ve seen other Tesla modules for sale, I’d appreciate a link, or information about the pricing.

DIY Programmable Lithium Ion Charger Shield

Update:  According to this comment on Dangerous Prototypes, the charger chip’s support for lithium ion charging is quite primitive, and so this project depends on the Arduino to properly manage the charging. Too bad.

ElectroLabs has published a nicely documented programmable single/multi cell lithium battery charger shield for Arduino. It is based on the LT1510 Constant Current/Constant Voltage Battery charger IC.

Features include:

  • Display for battery/charge status and configuring charging parameters
  • 50mA 10 1.1A charging current.
  • 2-10V charge cut-off voltage

Those voltages don’t make a whole lot of sense for Lithium Ion, but it appears the charger IC they are using also works with other chemistries.

I don’t know the BOM cost, but an assembled version is $75 on Tindie (ouch).

I don’t think I’ll be building one of these, but I am very interested in having examples of using commercial charger ICs outside their default configurations.

[via Hack-a-Day]