Jul 24, 2025 · 28m · catalyst
Repurposing EV batteries for grid storage
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gold bands on the timeline = statements, start to end. Hover to read, click to jump. CC turns on captions
In this episode of Catalyst, host Shayle Kann and Redwood Materials CTO Colin Campbell explore how retired electric vehicle batteries can be efficiently tested, aggregated, and repurposed for stationary grid energy storage before undergoing mineral recycling.
How this conversation actually went
Every chapter scored 0–10 on four independent dynamics. Hover any point for the reasoning behind the score. Shayle holds 45.8% of the talking time here. How this is scored →
Shayle as informed peer 6.7 Guest teaching 3.2 Guest disagreement 1.3 Shayle pushing back 2.8
speaking balance: gold is Shayle, purple is the guest (3 minute bins)
Sharpest disagreement ▶ 14:54 Campbell defends technical complexity
Campbell pushes back against Kann's suggestion that anyone could easily plug old packs into the grid, highlighting the engineering required for heterogeneous high-power electronics.
Hardest push from Shayle ▶ 14:44 Kann probes for the core innovationKann bluntly challenges Campbell's oversimplified description of wheeling packs into a field, asking where the defensible innovation actually exists.
Biggest teaching moment ▶ 10:58 Campbell explains the additive lifecycle detourCampbell corrects the premise that recycling and grid deployment are mutually exclusive choices, explaining Redwood executes grid storage as an interim step before mineral recovery.
Shayle holds their own ▶ 25:22 Kann dissects duration economicsKann demonstrates expert knowledge of battery discharge rates and linear cost scaling for multi-hour storage, earning explicit praise from Campbell for his framing.
the scores for every segment, with the reasoning behind each
| Chapter | Topic | Shayle as informed peer | Guest teaching | Guest disagreement | Shayle pushing back | Why |
|---|---|---|---|---|---|---|
| Assessing Condition and Chemistry of Retired EV Batteries | 6 | 3 | 1 | 1 | Kann guides the discussion with solid background knowledge of battery degradation metrics and chemistry timelines. Campbell explains that EV packs usually arrive in very good condition with roughly 80% remaining capacity. | |
| The Economic Calculus of Repurposing Versus Recycling | 8 | 4 | 2 | 3 | Kann articulates a first-principles economic comparison between recycling cathode active material and grid repurposing against new LFP packs. Campbell reframes the issue by pointing out that repurposing is an additive detour before ultimate metal recovery. | |
| Engineering Integration and Redwood's Feedstock Advantage | 7 | 4 | 2 | 6 | When Campbell claims Redwood simply wheels packs into a field and plugs them in, Kann pushes back directly to demand where the actual technical innovation lies. Campbell explains the proprietary power electronics, site engineering, and software required to integrate heterogeneous packs. | |
| Forecasting Market Volume and Grid Capacity from Retired EVs | 6 | 3 | 1 | 2 | Kann presses Campbell on specific capacity figures, clarifying whether the five gigawatt-hours quoted is rated nameplate capacity or degraded available capacity. Campbell provides annual production and deployment benchmarks. | |
| Mid-Roll Sponsor Announcements: Bloom Energy, Engie, and Energy Hub | 5 | 2 | 1 | 1 | Following mid-roll sponsor reads, Kann queries how the incoming stream will be partitioned between EV packs and consumer electronics, and how LFP chemistry impacts the model. Campbell confirms their power electronics are chemistry-agnostic. | |
| Leveraging Retired Batteries for Long-Duration Energy Storage | 8 | 3 | 1 | 4 | Kann shows deep domain expertise regarding C-rate degradation and explains why lithium-ion is rarely deployed for 20-hour duration due to linear capex scaling. Campbell agrees with Kann's framing and outlines Redwood's target gigawatt-hour deployment. |
Statements from this episode (13)
Redwood Materials finds retired EV batteries typically lose only 20% capacity
“So from a physical perspective they're usually almost new. And then from an electrical and electrochemical perspective we receive them when a customer might get frustrated with them, typically. So that's something like I've lost 20% of my range, or the acceler…”
Redwood receives mostly 10-year-old NMC EV batteries for recycling
“Today they're predominantly NMC. You could think of it as what we get is what was built roughly 10 years ago. So we're time shifted from the manufacturing trends.”
Redwood repurposes 95% of retired EV batteries for grid storage before recycling
“We don't have to choose, right? So we Typically we'll do both. We will send a battery out to a grid scale energy storage site to provide grid services when that is economically sensible, which is 95% of the time, and then we will go on to recover the metals va…”
Second-life EV batteries require just one to two years to become profitable
“The life of the second life battery on the grid is, it's certainly long enough to be economically valuable, and that, in order to make economic sense, it's really one or two years, hundreds of cycles, low hundreds of cycles.”
Redwood repurposes retired EV battery packs without opening them or removing modules
“We do a very brief electrical inspection. Something like five minutes, cell balance impedance check, and we literally wheel it out to the field where we have a spot for it and plug it in. So we are not opening up the packs. We are not removing the modules. We …”
Redwood Materials collects over 80% of US end-of-life EV battery packs
“We are already collecting north of 80% of the end of life EV packs across the nation.”
About 5 GWh of EV battery capacity retires annually in the US
“So today it's on the order of five gigawatt hours a year that's coming off the road.”
New US EV production accounts for roughly 150 GWh of batteries annually
“And it's on the order of, ah, a 150 gigawatt hours a year new EV production that's going into service.”
EVs consume 80% of battery production, driving future second-life grid supply
“I think it's something like 80% of the energy storage is going into EV. So that's where most of the gigawatt hours are going to come out. Which is really good for grid storage because those are the packs that are going to be easiest to redeploy. Those are the …”
Proprietary power electronics allow Redwood Materials to use any battery chemistry
“We're totally agnostic to chemistry type. So because of the power electronics that we've developed, we can really easily integrate low capacity, high capacity, high nickel, LFP new, old, low voltage, high voltage packs, whatever it is we're ready to plug it in…”
Repurposing used LFP batteries for grid storage remains economically viable
“The economics are different for LFP, but they still solve. The metals values are lower. The cycle life is different. The degradation is different. The energy value is different, but it still makes sense to deploy them on the grid used LFP packs.”
Second-life EV batteries excel in four-to-twenty-hour long-duration grid storage
“We can certainly play in the two hour, four hour markets with repurposed EV packs, second life packs. Where we see them really starting to shine, though, is in the longer duration. Markets. So four hour, eight hour, maybe longer, maybe 20 hour. And that's beca…”