It’s been nice to see the growing popularity of electric vehicles these last few years, but EVs need batteries and batteries don’t last forever. In fact, the first generation of EV batteries are already dying, and there’s an absolute dead battery typhoon coming. Lithium battery recycling is improving, but it’s still far from where it needs to be. Luckily there’s another option that’s pretty simple. Just take those used batteries and repurpose them for less demanding large scale energy storage. That’s exactly what’s happening at a recently opened 25 MWh grid scale energy storage system in California. But if these batteries are “dead,” how are they able to bring new life to renewable energy storage?

If you can get quality grid-scale storage from just daisy chaining a bunch of car batteries together, then why aren’t they everywhere? And why would someone string 1,300 “dead” car batteries together in the first place? The reasons might surprise you, but this weird solution will make sense in a minute.

California is famously sunny and warm. To beat the heat, many Californians rely on air conditioning. As you might expect this leads to a significant power draw during the day, which is not a huge problem as that’s when renewables are generally most productive.1 But the draw actually climbs even higher at night when people return to their homes, which is unfortunately right when renewables like solar start to fall off.1 So how does the most populous state handle these massive energy swings?

Right now, the answer is “peaker plants,” whose purpose – as you can probably guess from their name – is to supply not-quite-emergency power during these peak times. “Great, problem solved!” right? Well, not quite, because peaker plants get their power from natural gas. To be clear, natural gas isn’t as bad as oil or coal, but it’s still a fossil fuel that gets burned and puts carbon into our atmosphere.2 To quote the California Energy Commission Chair, Dan Hochschild, “Peaker power plants are the most expensive, least efficient, [and] most polluting part of our fleet.”3 Sure would be great if they could switch to renewables, but that brings us to our next problem, one that viewers of this channel will be all too familiar with: effective energy storage. It’s why I’m obsessed with this topic.

Luckily, electric vehicles are helping with decarbonization, just in their own way. They’ve been with us for years now and are becoming increasingly affordable and popular.4 For perspective, back in 2012, just 120,000 electric cars were sold worldwide. In 2021, more than that are sold each week.4 Unfortunately, all those cars are powered by batteries that will need to be replaced eventually. What the heck are we going to do with all of those batteries!? Well, reduce, reuse, recycle, right? We don’t want to see a reduction in electric cars and their batteries for plenty of reasons, so let’s not reduce here. Lithium battery recycling has made some great strides recently, with groups like Redwood Materials, Recyclico, and Li-Cycle working hard to make this process easier and more efficient.56 But the coming flood of used batteries, (or battery flood, which is coincidentally, the name of my new metal band) is a challenge too big for recycling to handle alone. That leaves us with reuse, but how can we reuse “dead” car batteries?

This brings us back B2U Storage Solutions and their seemingly super simple answer to all these issues. They’ve taken approximately 1,300 used Nissan and Honda batteries and strung them together to form the SEPV Sierra hybrid solar storage facility.7 Based in Lancaster, California this 25MWh facility is likely the largest, fully operational “second-life” battery storage facility on planet earth.7 But if these old EV batteries are dead, how does this even work? Has B2U discovered some sort of battery necromancy? (Actually, Battery Necromancy is the name of my new metal band)

Nope, way simpler than that.

If you own a rechargeable device (I’m willing to bet you do) you’re aware that their ability to hold a charge diminishes over time. The reasons for this are a little complicated, for more information check out some of our videos on batteries. But suffice to say, Li-ion batteries remain the gold-standard in consumer goods, especially in EVs, for plenty of reasons. This includes their solid capacity and longevity, their good energy-to-weight ratio, power density, swift charge/discharge times, affordability, reliability and so on.8 But life for a lithium-ion battery in an EV is pretty demanding, and once a battery starts to go, usually when it’s only able to hold around 70 to 80% of its charge, it can no longer live up to these standards and should be replaced.9 10

But hey, a battery’s life doesn’t end at around 80%, there’s still plenty of good times left in its golden years, just maybe not inside a brand new Tesla. Stationary, intermittent renewable storage is actually a great home for aging batteries, because in this application they’re allowed to charge and release energy more slowly, and the cycling needs and other demands are generally less intense than in a high performance vehicle. But their efficiency, reliability and safety are still appreciated.11 This is backed up by a 2019 McKinsey sustainability report, which found that even after 10 years an EV battery can be reused in markets that need stationary energy storage with less frequent cycling.12

Again, back to B2U, who saw the coming battery-pocalypse (okay, no this is the name of my metal band). Anyway, B2U put 2-and-2 together, and voila, turned these mountains of EV batteries into a grid scale storage facility. So, I know I said the solution was simple, but it’s not quite as easy as hooking a bunch of old car batteries up to some solar panels in the desert. There are some unresolved challenges to this, which we’ll get to in a minute, but more challenges have been solved than not.

One such challenge is the batteries themselves. With 1,300 batteries, all of different ages, from different makes and models of car, in different states of degradation … there’s a lot of variables to manage.13 Especially since we have literal tons of batteries working in sequence, and we don’t want the older or weaker ones to slow the system down. There’s also some safety concerns. Lithium batteries are notoriously (if, in actuality, very rarely) susceptible to overheating leading to dramatic cases of thermal runaway. Stacking a bunch of these batteries together in parallel strings in an especially warm and sunny state might seem like a disaster waiting to happen.

It’s here that B2U’s biggest innovation comes into the picture. Their software, in tandem with their cabinet controllers, monitors all those battery variables during charge and discharge cycles. It can connect and disconnect the batteries as needed, allowing the older batteries to take a break before they drag down the performance of their buddies. B2U CEO Freeman Hall claims that “this approach enables our system to achieve efficient energy yield despite the variance in capacity inherent in second life batteries.14 On the safety front, B2U’s EPS cabinet controllers monitor the health of individual batteries and flag situations where there are potential problems that can affect future performance. The operators can also set strict safety parameters and if any battery deviates from these guard rails, the pack is automatically disconnected, allowing it to cool down and be dealt with rather than risking disaster.15

This brings us to another innovation from B2U. Lithium car batteries are usually made up of thousands of roughly double-A-sized batteries, literally glued together. Close to 7,000 of them for a Tesla.16 Part of the reason it can be challenging to recycle or repurpose these batteries is because you normally have to break apart each pack to get to the individual cells. But not so for the Sierra facility. Their cabinets are designed to accept packs as they are, instead of having to jail-break each individual cell, which saves them time and money and allows replacement batteries to easily be tagged in when the time comes.17 Combined with their cabinet controllers and software designed to translate commands across different battery makes, means they’ve made the process of reusing batteries in grid-scale storage much cheaper – an estimated 40% cheaper.18 Hall claims it costs less than $200 per kilowatt hour to install, which is well below the norm for a lithium-ion storage plant.19 For context, a National Renewable Energy Lab study put the cost for a similar facility in 2023 at around $283 per KWH. And they didn’t project costs to dip below that $200per KWH until 2030!2020

And speaking of money, the EPS controller doesn’t just monitor the batteries, it monitors the market for the best deals too. By taking advantage of both predictable daily price shifts and unexpected price hikes, it automates bids and sends them directly to the California grid.17 Tesla has similar functionality with their Megapack installations. Essentially, it collects energy while the sun is shining, then when people get home at night it sells that energy to the grid when it’s most desired and valuable. A sort of “buy low, sell high” arbitrage strategy that has generated over $1 million in revenue for B2U in 2022.18 The fact that they’ve already proven they’re financially successful probably makes them more appealing to investors and lawmakers, which hopefully means more plants like this in the future.

The SEPV plant has already proven that it’s an affordable, reliable, and effective grid-scale storage solution for solar energy. It offers a home for older batteries and seems ready and able to start replacing those gas-burning peaker plants. That all sounds incredible, so what’s the catch? There’s always a catch. And yes, as we alluded to earlier, some challenges do remain.

B2U is mostly working with Nissan and Honda,13 so their system is largely designed around dimensions and shapes that work with those. If the batteries deviate from the standard shape, it might diminish some of the benefits of B2U’s ‘plug n play’ system. Though, at least on the software side, tests on the Chevy’s Bolt and Tesla’s Model 3 show the EPS system can communicate with just about any EV battery model.20 Ironically, the biggest issue is that the system is small. 25 megawatt hours of storage is a great start, but for context, peaker plants like the Hanford and Henrietta plants have 95 megawatt capacities each.2122 We’re going to need a lot more (or bigger) SEPV storage facilities and accompanying renewable power plants if we want to dump those polluting peaker plants.

But all in all these are some pretty minor hurdles to jump. Ultimately, B2U’s Sierra SEPV facility shows that we don’t have to wait for the next big battery paradigm shift to “up” our renewable energy storage game. The technology is already here, it’s safe, it works well, and it’s relatively inexpensive. As EVs become more popular and age there’s going to be no shortage of supplies. Plus, it’s not like the sun is going anywhere for another 5 billion years either.23 Speaking of which … B2U’s set-up isn’t limited to solar storage. There’s a lot of wind power in California, Texas and other states that could really benefit from a similar storage solution. Hopefully we will see more plants like this sooner rather than later.

  1. Energy Upgrade California ↩︎
  2. What are the safest and cleanest sources of energy? – Our World in Data ↩︎
  3. From Idea to Reality – Battery Storage Comes of Age on the California Grid ↩︎
  4. IEA – Global EV Outlook 2022 ↩︎
  5. Tesla co-founder has a plan to become king of EV battery materials—in the U.S. ↩︎
  6. The Lithium-ion Battery Boom & the Need for Recycling ↩︎
  7. B2U Storage Solutions Announces 25MWh of Second-Life EV Battery Capacity is Operational at its Hybrid Solar + Storage Facility in Lancaster, CA ↩︎
  8. DOE – Batteries for Electric Vehicles ↩︎
  9. The big reuse: 25 MWh of ex-car batteries go on the grid in California ↩︎
  10. Electric vehicle batteries alone could satisfy short-term grid storage demand by as early as 2030 – Journal of Nature Communication ↩︎
  11. Power System Design: Why Lithium is Taking Over Stationary Energy Storag ↩︎
  12. McKinsey Sustainability – Breathing new life into used electric vehicle batteries ↩︎
  13. Second Life: How One Energy Storage Company Plans on Recycling EV Batteries ↩︎
  14. B2U reaches 25 MWh storage capacity at California facility with 1,300 used Honda and Nissan EV batteries ↩︎
  15. Second life energy storage firm B2U expands California project to 25MWh ↩︎
  16. Tesla – A Bit About Batteries ↩︎
  17. 1300 recycled electric vehicle batteries used for biggest grid-scale storage system of its kind ↩︎
  18. EV batteries getting second life on California power grid ↩︎
  19. Canary Media – How a company turned used Nissan Leaf EV batteries into moneymakers ↩︎
  20. World’s largest used EV battery power facility in California ↩︎
  21. Hanford Peaker Plant ↩︎
  22. Henrietta Peaker Project ↩︎
  23. NASA – Our Sun ↩︎

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