Remembering Coda Automotive

It is always a pleasure to talk to people who contact Elithion with inquiries; with one noticeable exception: Coda Automotive.

Two years ago, we got a call from the Senior VP of Engineering at Coda Automotive. If memory serves, the gist of the call was this:

  1. Elithion owed Coda a free BMS because Coda was such a great company and Elithion was a peon of a company
  2. Coda was not going to wire the Elithion BMS as required, because Coda engineers were world experts in this field and Elithion didn’t know what the heck it was doing
  3. Coda planned to use battery modules that the car owner could hot swap  (!)

(Today, we are grateful to that same man, because, as president of EEtrex, he is shedding EEtrex’ best talent, and Elithion is busily hiring them.)

I have just reread my email correspondence with the Coda engineer at the time, and they confirm my recollections.

When the Coda engineers came to terms with the fact that they weren’t going to get a free BMS from Elithion, and that the Elithion BMS was Coda’s first choice, they finally relented and placed an order for one ($ 2911).

In the process of due diligence, I tried to asses whether the BMS would be used properly; but they very honestly told me, that, no, they would not let the BMS protect their battery.

So I wrote them: “Thank you for taking the time for researching those questions and providing me with the answers, which indicate very clearly that, unfortunately, our products are not compatible with yours. “;  “Please use our BMS selector to select a BMS that will work in your application: http://liionbms.com/php/bms-selector.php “; and “Even though Elithion was not able to provide you with a solution, I hope that I was able to help you in your assessment of your technical needs. I would like to wish you the best in your project. ”

To its credit, Coda did put out 100 cars. But, presumably, they did so without a fully functioning BMS.

Therefore, it is with poorly hidden schadenfreude that today I read about the bankruptcy of Coda Automotive.

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Hired Steve Mayer as General Manager

It is my pleasure to announce that today Elithion hired Steve Mayer as the General Manager.

Steve will be responsible for management, business development and mechanical engineering.

Steve was the Senior Project Manager at EEtrex since 2008, where he lead the development of key technologies.

Steve has a BS in Mechanical Engineering and an Masters is Engineering Management (BYU).

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EEtrex: the end of an era

EEtrex (a company with which Elithion has some indirect connections) is in bad shape.

On Wednesday it laid off a great number of employees, leaving only a skeleton crew in place.

One of the people who lost her job was N. B., who, together with me and 3 others, co-founded Hybrids Plus in 2006. In 2009, the newly formed EEtrex took over the assets of Hybrids Plus, and N.B. continued working at the new company.

To be sure, EEtrex is still open. But, in my thinking, the fact that EEtrex lost N.B. signifies at least the end of an era, and possibly the last nail in the coffin of what was once EEtrex.

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Enerdel battery blocks with BMS

In cooperation with Enerdel, Elithion now offers 1.5 kWh, 48 V Enerdel battery blocks with and integral BMS board, ready for easy inclusion in your high performance traction pack for a race EV.

One to 16 modules may be used for traction packs from 44 to 700 V, from 1.5 to 20 kWh, from 40 to 700 kW peak power.

A BMS master is also required for each system.

Please contact Elithion for more information.

 

 

 

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“Battery Power Management for Portable Devices” (Yevgen Barsukov and Jinrong Qian) , review

It has been my great pleasure to read a pre-release version of the book “Battery Power Management for Portable Devices“, by TI scientists Yevgen Barsukov and Jinrong Qian, and to then write a foreword for it.

Battery Power Management for Portable Devices

The book will come out in May 2013, but I’d like to share my thoughts about it today.

In contrast to my own book, “Battery Management Systems for Large Lithium-Ion Battery Packs “, this new book covers the other side of the spectrum: small batteries.

Some background is of order: open a small battery pack (such as for a laptop computer) and it is likely that the ICs on the protector PCB have a part number that starts with “bq“. If so, those ICs are made by Texas Instruments, and chances are that they use inventions and developments by the authors of this book. In other words, learning about small batteries and they management systems from this book is to learn directly from the masters who have, dare I say? the most intimate knowledge of how to make a safe and effective, small Li-ion battery.

And it shows.

The book is full of great information of the whys and hows of Li-ion cells, Small battery Management Systems, “fuel gauge” algorithms, communications with the host, and even how to prevent cheap knock-offs. It is a very practical book, complete with sample circuits (all using TI chips, of course, to the detriment of the competitors) for notebooks, cell phones, smart phones, and laptops.

TI’s patented “Impedance track” algorithm, arguably the best method to evaluate the State Of Charge of a cell or battery, is described in every detail, revealing all its glory.

The version I read was not yet proofread, and reflected the fact that the authors are not native English speaker (nor am I, for that matter). It lacked a few articles, but also had charming terms such as “back-bust” converter, with its vaguely sexual connotation. By the time the book will be printed, I trust it will be cleaned up (hopefully more than my own book, which went to press with too little proofreading and lots of errors).

The book is a great read for the designer of small batteries, engineering students, and technical managers. It is well organized, it flows nicely and yet it explores its subject in great depths. I cannot recommend this book enough.

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Unlike Dreamliner battery, Elithion batteries are safe

The only way that a battery manufacturer can insure the safety of a battery is if a switch is included in the battery and the BMS has full control of that switch.

The Li-ion batteries in the Dreamliner do include a BMS, but do not include a switch (the output terminals are always live). Therefore, if the BMS did detect a problem, it was powerless to fix it, as it had no switch to turn off.

On the contrary, Elithion batteries do include a switch, that is off by default, unless the BMS turns it on when it sees that the battery is safe. That is true of Elithion’s traction packs and of Elithion’s Lithiumod battery modules.

Therefore, Elithion can correctly claim that its battery packs are inherently safe.

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Boeing Dreamliner Li-ion battery fire

The entire fleet of Boeing Dreamliner aircrafts is grounded, because of a fire in a Lithium-ion battery. What do we know about the cause of that fire?

The cells:

Li-ion cells from GS Yuasa

  • LPV65, made by GS Yuasa.
  • Small prismatic, metal case, safety vents on the side
  • Standard Li-ion (LiCoO2) cell, which may suffer from thermal runaway
  • Specs: 65 Ah,  3.7 V nominal, 4.0 V at end of charge
  • Very High power handling: a short discharge time of 41 s places it in the top 20 % for Li-ion cells

 

 

 

Battery:

Battery pack for the Boeing DreamlinerMechanically:

  • Metal case
  • Approx 28 x 28 x 25 cm (11 x 11 x 14″)
  • Approx 28 kg (63 lb)
  • 2-pole blind mate power connector, Anderson power
  • Circular screw-in multi-pole control connector
  • The case does not seem to provide any space for the cell vents, should they open: the vents of at least 1/2 of the cells appear to be right against the outer walls

Electrically, power circuit:

  • 8S1P arrangement
  • 29.6 V nominal, 32 V max
  • 65 Ah, 1.9 kWh
  • 580 A peak, 17 kW peak
  • 5 mOhm internal resistance
  • Fuse between 2 and 3rd cell
  • No switch: the battery output is always live, and the BMS cannot directly protect the battery

Electrically, control:Dreamliner battery wit top removed

  • Centralized BMS, in two boards
  • Multiple wires to 8 cells, to sense cell voltages, with redundant connections
  • Multiple thermistors to sense cell temperatures
  • Hall Effect current sensor on board, output bus bar through it

 

The event

  • The damage occurred inside the case and was contained by it
  • The cells and all other battery components are relatively intact, though blackened and covered with the remains of burned materials
  • The only component that actually burned may be the translucent plastic sheet placed above the cells
  • The most evident effect may have been just the white smoke that is typically released by abused Li-ion cells’ electrolyte

The findings

My hypothesis

1) Over charge due to unbalance

The battery was not top balanced. Therefore, the 32 V was not equally divided into the 8 cells, meaning that some cells were at higher than 4 V, and therefore over-charged. LiCoO2 cells are prone to thermal runaway if overcharged.

2) Charging over current

The charger is capable of sourcing a very high current (on the order of 1000 Amps). The battery was discharged when the charger was turned on. The charger was able to overcome the very low resistance of this battery, and pump a very high current into it, at 32 V.
For example, it the battery was at a discharged voltage of 25 V (3.2 V / cell), then the current would be (32 – 25) / 5 mOhm = 1400 A.
The cells overheated and went into thermal runaway.

 

The underlying problem

  • Either the BMS did not detect the over temperature, over voltage on a cell, or over current
  • Or, the BMS detected the problem, but did not report it to the aircraft; the BMS had no recourse, as the battery does not have a switch that the BMS could turn off
  • Or, the BMS did report the problem to the aircraft, but the aircraft did not obey the BMS and shut off the current
  • Or, the BMS did report the problem to the aircraft, but the aircraft did acknowledge the problem, but it had no recourse, as it does not have a switch that it could turn off

 

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“Short Discharge Time”: a tool to compare cells and batteries in power applications

When selecting cells for a power battery, it is useful to have the ability to quickly compare various cell technologies, and calculate the resulting pack resistance and efficiency, independently of capacity, voltage or chemistry.

Here we propose a way of doing so, using the “Short Discharge Time”, the theoretical time required to discharge a full cell (or battery) through a short circuit. This constant is a characteristic of each battery cell technology, regardless of capacity, voltage or chemistry.

A lower Short Discharge Time indicates that the cell or battery is more efficient, which is important in power applications.

Short Discharge Time is calculated as:

short_discharge_time [h] = capacity [Ah] * resistance [Ω] / voltage [V]

Where:

  • Capacity is the nominal capacity of the cell or battery
  • Resistance is the DC resistance of the cell or battery at 50 % SOC
  • Voltage is the open circuit voltage of the cell or battery at 50 % SOC

Seconds is a more practical unit of short discharge time than hours:

short_discharge_time [s] = 3600 * capacity [Ah] * resistance [Ω] / voltage [V]

Short Discharge Time ranges from about 20 s (high power pouch cells) to about 200 s (Li-sulfur).

Of course, Short Discharge Time is just one parameter to consider. Others include energy density, cost, ease of connection and maximum rated current.

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Elithion: four years and counting

Four years ago today we chose the name “Elithion” (meaning “Electronics for Lithium ion”); we immediately grabbed the “Elithion.com” domain, and Elithion was born. The formation of an LLC was completed 9 days later.

Today, Elithion is a small but thriving corporation, with:

  • A complete product line of battery management systems (BMSs)
  • About 1000 systems installed, protecting an estimated 80,000 cells
  • Production of custom traction battery packs
  • A line of battery modules for stationary applications
  • Good name recognition and reputation
  • Six employees, a network of consultants, and a board of advisers formed by industry leaders
  • Product manufactured locally by 3 assembly houses, plus in-house final assembly and QA
  • Ability to ship product usually within 14 hours, and at most in 1 week

When we started four years ago, the only other providers of off-the-shelf BMSs were REAP and Lithium Balance. Today, there are some 40 companies offering (or claiming to offer) off-the-shelf BMSs. Of those, in our opinion, only 8 of them offer a quality BMS, and actually produce it: Clayton, Elektromotus, Elithion, Ewert, Ligoo, Lithium Balance, Tritium and Reap. Despite the competition, Elithion stands out with a strong name recognition  and reputation, in part thanks to the book “Battery Management Systems for Large Lithium-Ion Battery Packs “, which today is the authoritative book on the subject.

Elithion is self funded, and growing organically. With its small team it has developed products which larger companies develop using 1 million dollars, 2 years, and a team of 15 engineers.

We’re done well for ourselves.

Here is to more years of organic growth!

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Too small to fail

Over the years, various times companies designing a product asked us whether we would be able to ramp up production of our BMS to meet their production plan. We assured them we could, yet we did not get many orders on the grounds that we were too small a company.

Yet, today, we’re still around and thriving, while many of those very same companies are gone.

  • Better Place (May ’13, $ 800 M, EV infrastructure) – gone
  • Envia Auto (EV infrastructure) – gone
  • Evida (Dec ’12, $ 10 M, EV batteries) – gone
  • SAAB (Jan ’12, Auto manufacturer) – bankrupt
  • Coda Automotive (May ’13, $ 100 M, Auto manufacturer) – gone
  • Bright Automotive (vehicles) – gone
  • Azure Dynamics (motor drivers) – gone
  • Imara (cells manufacturer) – gone
  • A123 (Oct ’12, $ 500 M, cell manufacturer) – bankrupt
  • Zenn (vehicle manufacturer) – no longer able to make cars
  • EVX (vehicle manufacturer, X-prize contender) – offered to buy Elithion – gone
  • Arelec (Swiss, energy) – gone
  • Junco (battery packs) – gone
  • The Street Group (Motorcycles) – gone
  • Hi Tech Developments (battery packs) – gone
  • Ecos Motors (EV conversions) – gone
  • Energy Generation Technologies (battery packs) – gone
  • Red Cloud EV (vehicles) – gone
  • Jungle Motors (PHEV conversions) – gone
  • EV Performance Warehouse (wheeler and dealer) – mercifully gone
  • US United Energy Systems (wheeler and dealer) – mercifully gone
  • Ally Automotive (EV conversions) – good riddance!

My favorite story is about Technics (a vehicle manufacturer from Taiwan) . “CG” got very incensed with us: “I want to buy battery packs and in considerable amounts starting now, not follow links to some website, I simply don’t have the time nor the desire. It’s you’re product and I leave it up to you to specify and if you can’t, don’t.”. Well, Technics is gone, and “CG” if probably off to licking his huge, bruised ego.

We’re here to stay, and we’ll serve you, now with your prototype needs, and later (in our sincere hope that you are still around) with your production needs.

 

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