Climate change is forcing governments and businesses all over the world to improve environmental sustainability by limiting industrial pollutants and CO2 emissions and subsidizing the transition from fossil fuels to greener, more energy-efficient technologies. Because of this, multicell electric batteries are being increasingly used in public and private transportation, sustainable energy storage, airspace and defense, unmanned vehicles and robotics, and other fields. Multicell batteries can vary in complexity, scale, cell’s chemistry, form factor and count, but despite the variety, they all face one common problem of uneven cell aging.
Subjected to multiple charging and discharging cycles each battery cell is degrading at its individual, hard-to-predict pace. Over time cells exhibit different residual health and charging capacity. Some cells fail prematurely, impacting the overall battery autonomy, reliability and operational life.
Just a few faulty cells might require a costly replacement of the entire battery. This is because the output of conventional multi-cell batteries is limited by the voltage and internal resistance of their weakest cells, no matter how healthy and charged the rest of the cells are. A stressful load on the weaker cells is wearing them out at a faster pace, accelerating with every power cycle. Thus, the states of cells tend to diverge over the lifetime of a battery: weaker cells degrade faster than the others and fail first.
To exclude this common precursor of the early battery failures, the industry is forced to opt for expensive, high-quality cells, matching them by initial capacity and voltage output. This important, albeit costly practice initially helps avoid problematic cells. However, right from the first discharging cycle every cell would still age at a different pace, subject to its chemical material qualities. While the modern battery management systems (BMS) do offer cell load balancing, they are still incapable of making cells age at a similar pace. The challenge of keeping cell health on a similar declining trajectory remains mostly unaddressed.
As a result, the low reliability of contemporary battery cells is inflating capital and operational expenses for battery users and inhibiting the wider adoption of the multi-cell battery technology.
Today’s electric vehicles rely on expensive batteries with thousands of cells, governed by intricate distributed battery management systems. Yet despite the larger number of allowed recharging cycles, automakers still can’t guarantee a million-mile EV range. Achieving it requires costly battery service, despite all the innovations that go into a modern electric car.
The problem is even more acute in the mission-critical application space. In-field cell replacement is rarely an option; owners must account for a regular professional battery service. Public buses are a great case in point, where battery packs are proactively replaced to avoid battery failures while on the go. Provisioning electric buses with spare battery packs is often economically unviable in smaller cities, impeding wider adoption of greener public transportation.
Proactive battery pack replacement also adds to staggering stockpiles of improperly disposed cells. They are highly toxic and expensive to take apart and recycle, adding to a fast-growing global e-waste problem. However, the majority of decommissioned cells are still in good enough condition to be repurposed for non-mission-critical applications such as solar energy home battery storage.
Yet selecting “good” cells is a time-consuming endeavor, requiring special recycling facilities, machinery, and professional staff to handle hazardous materials.
So, there we have it: the promise of a sustainable economy, running on clean, inexpensive electric battery power, is facing multiple technological, economic, and environmental challenges. And we're just scratching the surface by focusing on where the Nubacell architecture can challenge the global status quo and give users a better battery usage experience.
Stay tuned for our next blog, where we plan to explain the highlights of our technology.