Nvidia has spent the past year pushing data-center builders toward racks that draw a megawatt and run on 800 volts of direct current, an architecture that promotes energy storage from a backup accessory in a room down the hall to a component of the rack's own power design. That is the single most-cited reason to own a battery company right now. It is worth checking who actually gets the order.

The answer, so far, is contract manufacturers. Flex, the Singapore-based electronics manufacturer, launched an 800 VDC Power Rack built with Nvidia for the Vera Rubin platform, offering battery backup units and capacitor backup units as options on it. Delta Electronics, the Taiwanese power-electronics maker, shows in-row 660 kW racks with an 80 kW battery backup unit embedded per shelf. The cells behind those shelves come from Asian suppliers. None of the three US-listed battery names most often attached to the theme are in that path.

The incumbent sells the room, not the rack

EnerSys makes stored-energy systems for industry: uninterruptible power supply strings and DC power for telecom and data centers, forklift batteries, and defense cells. Its business is genuinely inflecting. In the quarter ended 5 July, revenue rose 4.8% to $935.6m while gross profit climbed 23.7% and operating income 75.1%. Data-center orders were up 80% with 12-to-36-month visibility, and total book-to-bill ran 1.06x. Its answer to the lithium transition, the DataSafe Noir cabinet launched in June, claims more than twice the output power of published rival specifications — and generates no revenue until fiscal 2028. That is facility-level equipment competing with Vertiv and Eaton, not rack content.

Two caveats sit inside the earnings. A $31m tariff refund added $0.63 a share; strip it and the 510-basis-point gross-margin expansion becomes 180. And $1.25 of the $3.66 adjusted diluted EPS was a Section 45X manufacturing tax credit, with second-quarter guidance implying that share rises toward 38%. The credit phases down from 2030 and expires in 2033, and its domestic-content threshold tightens each year — which is what the roughly $500m Greenville, South Carolina lithium plant is for.

Pipeline is not an order book

Eos Energy builds zinc-based grid storage — cubes sited beside substations and solar farms, outside the data-center fence. Revenue rose 351% to $68.8m and backlog hit a record $807m, up about a quarter sequentially. Gross margin remains negative at -71%, though that is the fourth straight improvement from -203% a year ago. Data centers are 32% of a $24.6bn opportunity pipeline; qualification for on-site co-location is still under way and nothing is contracted. Meanwhile the diluted share count grew 43% year on year, and $364m of cash faces a quarterly adjusted-EBITDA loss near $71m. Management trimmed the top of 2026 guidance to $350m from $400m, blaming a production-line consolidation rather than demand; consensus sits at $309m.

Phones, not infrastructure

Enovix makes silicon-anode lithium cells, and its customers are smartphone, smart-eyewear and drone makers. Second-quarter revenue was $9.0m, up 20.8% — a sharp deceleration from 85% growth three quarters earlier. It shipped 2,100 eyewear cells against a 50,000-unit order, and the lead smartphone customer's final qualification is not due to finish until end-2026. Chief executive Raj Talluri then resigned on 13 August to run Kulicke & Soffa, with the finance chief taking over on an interim basis; the shares lost 30% in five sessions on volume ten times normal.

What the prices say

EnerSys has nearly doubled over twelve months, but the shares are down about 10% from their May high and have traded sideways for a month, with the 50-day average now flat against the 200-day. The move was a re-rating: 19.9x trailing earnings today against roughly 11x a year ago, versus 14.4x forward and a 10.3% trailing free-cash-flow yield. Eos has fallen 47% in three months and is priced at 4.56x trailing sales against 3.16x forward — a spread that assumes revenue triples again. Enovix, down 66% over a year, still carries 19.3x trailing sales and 18.0x forward, meaning the market prices essentially no revenue inflection at all. Long-duration, pre-profit equities have also been fighting a 10-year Treasury yield near 4.64% after a 20-month high.

The setup

Where it stands — Only EnerSys converts data-center demand into profit today, and it does so outside the rack, at facility level. Would confirm — A named 800 VDC rack design win, or DataSafe Noir revenue pulled into fiscal 2027. Would invalidate — EnerSys data-center orders decelerating below book-to-bill 1.0x, or Eos converting none of its $807m backlog. Watch next — EnerSys fiscal Q2 results in early November; Eos third-quarter shipments against $300–350m full-year guidance. Valuation — EnerSys 19.9x trailing and 14.4x forward earnings, against roughly 11x trailing a year ago.