Second-Life EV Batteries Hit 50 MWh in Texas, But the Real Cost Advantage Stays Proprietary

B2U Storage Solutions announced September 9 that its Bexar Martinez battery energy storage system (BESS) entered commercial operation near San Antonio, delivering 28 MWh of grid services to ERCOT within CPS Energy's service territory^[1]. This is B2U's second Texas deployment, bringing the company's portfolio in the state to over 50 MWh, with roughly 100 MWh operating across Texas and California using more than 5,000 repurposed electric vehicle batteries^[1]. The milestone matters for grid resilience in one of the fastest-growing regions of the Texas market. But it also exposes a persistent transparency gap: B2U claims "significantly higher returns" and "lower-cost grid storage" than new-battery competitors^[1], yet publishes no $/kWh installed cost or $/kWh-cycled levelized figures that would let independent analysts, utility regulators, and competing storage vendors verify those claims.

Second-life EV batteries are thermodynamically sound for stationary storage. A pack that has cycled 80,000 miles in a Tesla or GM vehicle typically retains 80 to 90 percent of its original capacity, and the remaining cycles left on the pack, often 2,000 to 4,000 more charge-discharge events before reaching end-of-life thresholds, are well-suited to grid duty, where discharge depths are shallower and thermal swings less extreme than in mobile use. The scrap value of a used EV pack destined for recycling is roughly $50 to $100 per kWh; by aggregating, testing, and repackaging those cells into grid-ready BESS cabinets, a second-life integrator avoids the $150 to $200 per kWh cost of virgin LFP (lithium iron phosphate) cell procurement and can theoretically deliver installed systems at a materials cost advantage. B2U's patented EPS (EV Pack Storage) technology allows the company to deploy used battery packs "without modification," which it claims reduces the labor and engineering overhead^[7].

Yet "lower cost" in the abstract is not the same as "cost transparent." When a utility procurement officer or a municipal aggregator evaluates a 28 MWh BESS tender from B2U against offers from newcomers (Eos Energy, Energy Warehouse, Flux Power) or incumbents (Fluence, LG, Kokam), the decision hinges on installed $/kWh, round-trip efficiency, warranty depth, and degradation curves over the contract life. B2U advertises that its "projects deliver infrastructure investors significantly higher returns than those available from other domestic BESS vendors"^[1], a claim framed for equity buyers, not ratepayers. What it does not publish is the all-in cost to CPS Energy's grid and, by extension, to CPS customers. If Bexar Martinez cost $60 million to build and commission, that is roughly $2.14 million per MWh, or $21.40 per kWh of installed energy capacity. (Utility-scale BESS using new LFP cells typically runs $250 to $350 per kWh installed in 2024, 2025.) But without that number in a public filing, a regulator cannot check whether the storage was procured at fair value or whether B2U's cost advantage flows to the utility and then to ratepayers, or is captured as margin by the developer.

This is not unique to B2U. The broader second-life battery ecosystem, including Redwood Materials (battery refining), LG Chem's ESS division, and Nissan's xStorage pilot in the UK, routinely deflects cost queries on grounds of commercial sensitivity. The result is a market where the claimed advantage of repurposing (lower feedstock cost, extended asset life, reduced waste) coexists with a pricing black box. For grid economics and climate accountability, that opacity matters. A utility regulator reviewing a storage procurement has a fiduciary duty to determine whether the ratepayer is funding a genuine cost win or subsidizing a supply-chain arbitrage that benefits only the developer. Public filings, interconnection applications, power purchase agreements, NERC compliance certifications, carry cost data that disclosure rules in most states would require to be summarized in utility earnings reports or rate-case testimony. B2U and its peers resist that disclosure, framing detailed cost as proprietary.

The Bexar Martinez announcement also sidesteps a second transparency demand: ERCOT capacity markets and ancillary service revenues. If B2U's 28 MWh system earns $1 million per year in wholesale revenue (capacity, energy arbitrage, frequency regulation), and the developer captures $800,000 of that while CPS Energy retains $200,000, that ownership split is invisible in a press release. Utility procurement of storage increasingly bundles operational rights and revenue sharing; a ratepayer-owned utility or a public power authority should know upfront what the stored-energy earnings look like and who claims them. B2U's model, third-party development and long-term service agreements, is standard in infrastructure finance, but the terms should be auditable, not marketing spin.

The path forward is binding disclosure at the interconnection gate and in procurement filings. When B2U or any second-life BESS developer files an application to connect to a transmission or distribution network, the interconnection queue should require a summary cost table: installed $/kWh, expected round-trip efficiency, warranty cycle count and depth-of-discharge rating, and annual degradation rate. When a utility enters a power purchase or service agreement for storage, the capacity price ($/kW-year) and any energy or ancillary service revenue splits should be filed in the utility's next rate case or in a transparency docket. This would not reveal patented chemistry or cell-sourcing details; it would expose the financial claim being made on the grid and ratepayers. Regulators in California (CPUC), Texas (PUCT), and other RTOs already have precedent for requiring storage operators to disclose capacity and energy pricing in wholesale market filings. Extending that to developer-owned systems is not a ban; it is accountability.