NEW YORK, May 28, 2026 – Amprius Technologies (AAMI) experienced a dramatic rally Thursday, with its stock price climbing 26.5% to $21.70 on trading volume exceeding 13 million shares. The surge pushed the battery maker's market capitalization close to $3 billion, significantly outpacing the broader market, as both the SPY and QQQ indices gained less than 1%.
The sharp move came despite a lack of any single, clear catalyst. Instead, the rally appears to have been fueled by a confluence of factors: recent insider-sale filings, a bearish report from short-seller Manatee Research, and continued investor appetite for battery stocks with strong revenue growth. Amprius has not issued a new press release since May 19, when it announced a partnership with drone-delivery company Matternet.
Insider Sales and SEC Filings
SEC filings from May 26 revealed that CEO Thomas Stepien sold 60,702 shares at an average price of $14.7884 on May 21. The transaction was executed under a non-discretionary “sell-to-cover” plan to satisfy tax obligations related to the vesting of stock awards. Other insiders also sold shares: Chief Technology Officer Stefan Constantin Ionel disposed of 28,812 shares, and director Sun Kang sold 67,796 shares, both at the same average price. Additionally, director Donald Dixon filed a Form 144 notice for a planned sale of 17,895 shares, with a total market value of approximately $315,847, representing restricted stock units from equity compensation.
Short-Seller Report and Market Sentiment
Last week, Manatee Research announced it had taken a short position in Amprius, accusing the company of inflating order numbers, inadequate disclosures, and collaborating with weak manufacturing partners. While these remain allegations, they have sharpened trading activity in a stock already popular among momentum traders. The bearish bets add a layer of uncertainty to the company's near-term outlook.
Strong First-Quarter Results and Raised Guidance
Amprius reported first-quarter revenue of $28.5 million, a 153% increase year over year. The net loss narrowed to $5.0 million from $9.4 million in the same period last year. The company raised its 2026 revenue forecast to at least $130 million, reiterating its goal of achieving positive non-GAAP adjusted EBITDA. CEO Tom Stepien stated that Amprius enters 2026 “with momentum.”
Strategic Partnerships and Commercial Traction
The May 19 deal with Matternet provided further evidence of commercial progress. Amprius batteries already power Matternet's M2 drone, and the two companies are collaborating on next-generation batteries for future aircraft. Matternet CEO Andreas Raptopoulos emphasized that “every additional mile of range” improves network coverage, while Stepien noted that better battery performance expands “what is possible.”
Capital Structure and Dilution Concerns
Earlier this month, Amprius announced a plan to swap 2,726,631 shares for 7,128,458 public warrants, representing 62% fewer shares than if holders had exercised the warrants. This move aims to reduce potential dilution, but investors remain wary of the overall dilution risk from outstanding warrants and equity awards.
Peer Comparison and Risks
While other battery stocks also gained—Enovix up 3.8%, QuantumScape up 2.4%, and Solid Power up 3.6%—Amprius outperformed significantly, breaking away from the pack. However, risks remain. The company's 10-Q filing disclosed that three customers accounted for 49% of first-quarter revenue. Amprius also faces competition from larger, better-funded players in aviation and electric vehicles, and may require substantial capital spending and supply-chain upgrades to ramp production. The stock is currently trading more like a growth play under debate than a typical industrial, with the next challenge being to convert orders and guidance into actual deliveries and cash flow.
