The Quest To Find A Second Life For Electric Vehicle Batteries

Rechargeable lithium chemistry battery cells found their mass market foothold in the field of personal electronics. The technology has since matured enough to be scaled up (in both physical size and production volume) to electric cars, making long range EVs far more economical than what was possible using earlier batteries. Would the new economics also make battery reuse a profitable business? Eric Lundgren is one of those willing to make a run at it, and [Gizmodo] took a look at his latest venture.

This man is a serial entrepreneur, though his previous business idea was not successful as it involved “reusing” trademarks that were not his to use. Fortunately this new business BigBattery appears to be on far more solid legal footing, disassembling battery packs from retired electric vehicles and repacking cells for other purposes. Typically EV batteries are deemed “worn out” when their capacity drops below a certain percentage (70% is a common bar) but that reduced capacity could still be useful outside of an EV. And when battery packs are retired due to problems elsewhere in the car, or just suffering from a few bad cells, it’s possible to extract units in far better shape.

We’ve been interested in how to make the best use of rechargeable lithium batteries. Ranging from tech notes helping battery reuse, to a comparison of different types, to looking at how their end-of-life recycling will be different from lead-acid batteries. Not to mention countless project wins and fails in between. A recurring theme is the volatility of mistreated or misbehaving batteries. Seeing a number of EV battery packs stacked on pallets and shelves, presumably filled with cells of undetermined quality, fills us with unease. Like the rest of California, Chatsworth is under earthquake risk, and the town was uncomfortably close to some wildfires in 2019. Eric is quick to give assurance that employees are given regular safety training and the facility conforms to all applicable workplace safety rules. But did those rules consider warehouses packed full of high capacity lithium battery cells of unknown quality? We expect that, like the business itself, standards for safety will evolve.

Concerns on safety aside, a successful business here would mean electric vehicles have indeed given battery reuse a profitable economy of scale that tiny little cell phone and laptop batteries could not reach. We are optimistic that Eric and other like-minded people pursuing similar goals can evolve this concept into a bright spot in our otherwise woeful state of e-waste handling.

A Safer, Self-Healing Polymer Battery

Lithium-ion batteries are notorious for spontaneously combusting, with seemingly so many ways that it can be triggered. While they are a compact and relatively affordable rechargeable battery for hobbyists, damage to the batteries can be dangerous and lead to fires.

Several engineers from the University of Illinois have developed a solid polymer-based electrolyte that is able to self-heal after damage, preventing explosions.The material can also be recycled without the use of high temperatures or harsh chemical catalysts. The results of the study were published in the Journal of the American Chemical Society.

As the batteries go through cycles of charge and discharge, they develop branch-like structures known as dendrites. These dendrites, composed of solid lithium, can cause electrical shorts and hotspots, growing large enough to puncture internal parts of the battery and causing explosive chemical reactions between the electrodes and electrolyte liquids. While engineers have been looking to replace liquid electrolytes in lithium-ion batteries with solid materials, many have been brittle and not highly conductive.

The high temperatures inside a battery melt most solid ion-conducting polymers, making them a less attractive option for non-liquid electrolytes. Further studies producing solid electrolytes from networks of cross-linked polymer strands delays the growth of dendrites but produces structures that are too complex to be recovered after damage. In response, the researchers at University of Illinois developed a similar network polymer electrolyte where the cross-link point undergoes exchange reactions and swaps out polymer strands. The polymers stiffen upon heating, minimizing the dendrite problem and more easily breaking down and resolidifying the electrolyte after damage.

Unlike conventional polymer electrolytes, the new polymer also shows properties of conductivity and stiffness increasing with heating. The material dissolves in water at room temperature, making it both energy-efficient and environmentally friendly as well.

Lessons In Li-Ion Safety

If you came here from an internet search because your battery just blew up and you don’t know how to put out the fire, then use a regular fire extinguisher if it’s plugged in to an outlet, or a fire extinguisher or water if it is not plugged in. Get out if there is a lot of smoke. For everyone else, keep reading.

I recently developed a product that used three 18650 cells. This battery pack had its own overvoltage, undervoltage, and overcurrent protection circuitry. On top of that my design incorporated a PTC fuse, and on top of that I had a current sensing circuit monitored by the microcontroller that controlled the board. When it comes to Li-Ion batteries, you don’t want to mess around. They pack a lot of energy, and if something goes wrong, they can experience thermal runaway, which is another word for blowing up and spreading fire and toxic gasses all over. So how do you take care of them, and what do you do when things go poorly?

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Better Battery Management Through Chemistry

The lead-acid rechargeable battery is a not-quite-modern marvel. Super reliable and easy to use, charging it is just a matter of applying a fixed voltage to it and waiting a while; eventually the battery is charged and stays topped off, and that’s it. Their ease is countered by their size, weight, energy density, and toxic materials.

The lithium battery is the new hotness, but their high energy density means a pretty small package that can get very angry and dangerous when mishandled. Academics have been searching for safer batteries, better charge management systems, and longer lasting battery formulations that can be recharged thousands of times, and a recent publication is generating a lot of excitement about it.

Consider the requirements for a battery cell in an electric car:

  • High energy density (Lots of power stored in a small size)
  • Quick charge ability
  • High discharge ability
  • MANY recharge cycles
  • Low self-discharge
  • Safe

Lithium ion batteries are the best option we have right now, but there are a variety of Li-ion chemistries, and depending on the expected use and balancing and charging, different chemistries can be optimized for different performance characteristics. There’s no perfect battery yet, and conflicting requirements mean that the battery market will likely always have some options.

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Rescuing A Proprietary Battery Pack With A Cell From A Camera

If you have an older handheld battery-powered device, you may be fighting a diminishing battery capacity as its lithium-ion cells reach the end of their life. And if you are like [Foxx D’Gamma], whose device is an Alinco DJ-C7 handheld transceiver, you face the complete lack of availability of replacement battery packs. All is not lost though, because as he explains in the video below the break, he noticed that a digital camera battery uses a very similar-sized cell, and was able to graft the camera battery into the shell of the Alinco pack.

Cracking open the Alinco pack, he was rewarded with the rectangular Li-Ion cell and two PCBs, one for the connector and another for the battery management circuitry. By comparison the camera battery had a much smaller battery management PCB, and it fit neatly into the space vacated by the Alinco cell once those covers had been removed. A fiddly soldering job to attach the connector PCB, and he was rewarded with a working Alinco pack and an unexpected bonus when he found out that the transceiver was a dual band model.

Along the way he’s at pains to point out the safety aspects of handling Li-Ion cells, and to ensure that the polarity of the cell is correct. It’s also worth our reminding readers that these packs must always be accompanied by their battery management circuitry. The result though is pleasing: a redundant piece of equipment made obsolete by a proprietary battery, given a new lease on life.

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Solid State Battery From The Man Who Brought Us Lithium Ion

Who is [John Goodenough]? He’s 94, so he’s been around long enough that you ought to know him. He was one of the co-inventors of the lithium-ion battery. Think about how much that battery has changed electronics. [Goodenough] along with [Maria Helena Braga] may have come up with that battery’s successor: the solid state battery. There’s a paper available that is free, but requires registration. If you don’t want to register, you can read the news release from the University of Texas with no trouble.

Keywords used to describe the new battery are low-cost, noncombustible, long cycle life, high energy density, and fast charge and discharge rates. The pair is also claiming three times the energy density of a current lithium-ion battery. They also claim that the batteries recharge in minutes instead of hours. You can see a video from [Transport Evolved] that discusses the invention, below.

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Reverse Engineering A Nissan Leaf Battery Pack

Batteries wear out. If you are an electric vehicle enthusiast, it’s a certainty that at some time in your not-too-distant future there will be a point at which your vehicle’s batteries have reached the end of their lives and will need to be replaced. If you have bought a new electric vehicle the chances are that you will be signed up to a leasing deal with the manufacturer which will take care of this replacement, but if you have an older vehicle this is likely to be an expensive moment.

Fortunately there is a tempting solution. As an increasing number of electric vehicles from large manufacturers appear on our roads, a corresponding number of them have become available on the scrap market from accident damage. It is thus not impossible to secure a fairly new lithium-ion battery pack from a modern electric car, and for a significantly lower price than you would pay for new cells. As always though, there is a snag. Such packs are designed only for the cars they came with, and have proprietary connectors and protocols with which they communicate with their host vehicle. Fitting them to another car is thus not a task for the faint hearted.

Hackaday reader [Wolf] has an electric truck, a Solectria E10. It has a set of elderly lead-acid batteries and would benefit hugely from an upgrade to lithium-ion. He secured a battery pack from a 2013 Nissan Leaf electric car, and he set about reverse engineering its battery management system (BMS). The Solectria will use a different battery configuration from the Leaf, so while he would like to use the Leaf’s BMS, he has had to reverse engineer its protocols so that he can replace its Nissan microcontroller with one of his own.

His description of the reverse engineering process is lengthy and detailed, and with its many photos and videos is well worth a read. He employs some clever techniques, such as making his own hardware simulation of a Li-ion cell so that he can supply the BMS known values that he can then sniff from the serial data stream.

We’ve covered quite a few EV batteries here at Hackaday. Quite recently we even covered another truck conversion using Leaf batteries, and last year we featured a Leaf battery teardown. We’ve not restricted ourselves to Nissan though, for example here’s a similar process with a Tesla Model S pack.