AMPX SEC Filing News — Amprius Technologies, Inc.

Latest SEC filings for Amprius Technologies, Inc. (AMPX) explained in plain English. Covers insider buying and selling (Form 4), proposed insider sales (Form 144), material company events (8-K), and quarterly & annual reports (10-Q / 10-K). StrongBuyAnalytics provides navigation and brief excerpts or summaries; original filings remain at the SEC/source links and were authored by their filers, not StrongBuyAnalytics. Filing dates shown are source dates. Coverage and detection can be delayed or incomplete because of SEC availability, amendments, parsing, caching, or outages. Latest source filing date shown: 2026-09-28.

Amprius Technologies, Inc. develops, manufactures, and markets lithium-ion batteries for mobility applications. The company provides silicon anode lithium-ion batteries under the SiCore and SiMaxx product platforms. Its batteries are primarily used for existing and emerging aviation applications, including unmanned aerial systems, such as drones and high-altitude pseudo satellites. The company was founded in 2008 and is headquartered in Fremont, California.
Sector: Industrials Industry: Electrical Equipment & Parts Market Cap: $1.1B CIK: 1899287
20
Total Filings
0
Bullish Classifications
6
Bearish Classifications
9
Insider Transactions
4
Material Events (8-K)
1
Periodic Reports
Rule-based classifications for AMPX currently lean bearish. Of the 20 filing records displayed, 6 carry bearish classifications (such as insider sales or negative 8-K disclosures) versus 0 bullish. This does not necessarily signal fundamental deterioration — insiders sell for many reasons — but it is worth monitoring alongside the company's core financial metrics.
AMPX Filing Activity Snapshot 2026-06-04 — 2026-09-28
Insider Transactions (Form 4)
0 buys vs 6 sells
Net insider selling in this period — insiders sell for many reasons beyond conviction.
Largest Form 144 Filing
$2.36M
DIXON DONALD R · 2026-06-08
125,000 shares · Form 144
Form 144 Notices
6
Proposed insider sales filed — Form 144 is a notice of intent, not a confirmed transaction. Actual sales are confirmed via Form 4.
Insider Transactions 9 · Forms 3, 4 and 5

A Form 4 is filed within two business days of a company insider — an officer, a director, or a holder of more than ten percent of the stock — changing their position in the shares. All 9 filings in this group are Form 4s for Amprius Technologies, Inc.

The difficulty with reading these filings as a group is that a single form type covers transactions that mean entirely different things. An executive spending their own money to buy stock and an executive having shares withheld to pay tax on a vesting grant both appear as a Form 4. Every filing below is therefore tagged with the nature of the underlying transaction, taken from the transaction code reported on the form itself.

Across the 9 insider filings shown, the breakdown is 6 open-market sale and 3 compensation award. 6 of them involved a discretionary open-market trade; the rest are compensation and administrative mechanics.

What each transaction type means

Open-market sale ×6
The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.
Compensation award ×3
Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.
Form 4 Open-market sale Insider Selling 2026-08-25

AMPX insider Sun Kang (Director) sold 62,101 shares (~$642.2K)

Sun Kang, listed as Director at Amprius Technologies, Inc., reported an open-market sale of 62,101 AMPX shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code Nature Shares Price Value
S Open-market sale 62,101 $10.34 $642.2K
Filing: Form 4 (Insider Transaction) Insider: Sun Kang (Director) Shares: 62,101 Est. Value: $642.2K
View on SEC EDGAR → Open Filing Document →
Form 4 Open-market sale Insider Selling 2026-08-25

AMPX insider Stefan Constantin Ionel (Chief Technology Officer) sold 29,681 shares (~$306.9K)

Stefan Constantin Ionel, listed as Chief Technology Officer at Amprius Technologies, Inc., reported an open-market sale of 29,681 AMPX shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code Nature Shares Price Value
S Open-market sale 29,681 $10.34 $306.9K
Filing: Form 4 (Insider Transaction) Insider: Stefan Constantin Ionel (Chief Technology Officer) Shares: 29,681 Est. Value: $306.9K
View on SEC EDGAR → Open Filing Document →
Form 4 Open-market sale Insider Selling 2026-08-25

AMPX insider Stepien Thomas M (Director, Chief Executive Officer) sold 31,529 shares (~$323.6K)

Stepien Thomas M, listed as Director, Chief Executive Officer at Amprius Technologies, Inc., reported an open-market sale of 31,529 AMPX shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code Nature Shares Price Value
S Open-market sale 23,529 $10.34 $243.3K
S Open-market sale 8,000 $10.03 $80.2K
G Gift 5,000 — —
G Gift 5,000 — —
G Gift 5,000 — —
G Gift 346 — —
A Compensation award 346 — —
Filing: Form 4 (Insider Transaction) Insider: Stepien Thomas M (Director, Chief Executive Officer) Shares: 31,529 Est. Value: $323.6K
View on SEC EDGAR → Open Filing Document →
Form 4 Compensation award Tax / Compensation Filing 2026-06-16

AMPX insider Form 4 filed for equity award, exercise, or tax withholding

BAYLESS KATHLEEN A (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code Nature Shares Price Value
A Compensation award 10,423 — —
Filing: Form 4 (Insider Transaction) Insider: BAYLESS KATHLEEN A (Director) Shares: 10,423
View on SEC EDGAR → Open Filing Document →
Form 4 Compensation award Tax / Compensation Filing 2026-06-16

AMPX insider Form 4 filed for equity award, exercise, or tax withholding

SATTERTHWAITE LIVINGSTON (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code Nature Shares Price Value
A Compensation award 10,423 — —
Filing: Form 4 (Insider Transaction) Insider: SATTERTHWAITE LIVINGSTON (Director) Shares: 10,423
View on SEC EDGAR → Open Filing Document →
Form 4 Open-market sale Insider Selling 2026-06-16

AMPX insider DIXON DONALD R (Director) sold 85,000 shares (~$1.46M)

DIXON DONALD R, listed as Director at Amprius Technologies, Inc., reported an open-market sale of 85,000 AMPX shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code Nature Shares Price Value
A Compensation award 10,423 — —
S Open-market sale 85,000 $17.17 $1.46M
Filing: Form 4 (Insider Transaction) Insider: DIXON DONALD R (Director) Shares: 85,000 Est. Value: $1.46M
View on SEC EDGAR → Open Filing Document →
Form 4 Compensation award Tax / Compensation Filing 2026-06-16

AMPX insider Form 4 filed for equity award, exercise, or tax withholding

Chu Steven (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code Nature Shares Price Value
A Compensation award 10,423 — —
Filing: Form 4 (Insider Transaction) Insider: Chu Steven (Director) Shares: 10,423
View on SEC EDGAR → Open Filing Document →
Form 4 Open-market sale Insider Selling 2026-06-11

AMPX insider DIXON DONALD R (Director) sold 40,000 shares (~$765.2K)

DIXON DONALD R, listed as Director at Amprius Technologies, Inc., reported an open-market sale of 40,000 AMPX shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code Nature Shares Price Value
S Open-market sale 40,000 $19.13 $765.2K
Filing: Form 4 (Insider Transaction) Insider: DIXON DONALD R (Director) Shares: 40,000 Est. Value: $765.2K
View on SEC EDGAR → Open Filing Document →
Form 4 Open-market sale Insider Selling 2026-06-05

AMPX insider Stepien Thomas M (Director, Chief Executive Officer) sold 2,000 shares (~$41.9K)

Stepien Thomas M, listed as Director, Chief Executive Officer at Amprius Technologies, Inc., reported an open-market sale of 2,000 AMPX shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code Nature Shares Price Value
G Gift 30,384 — —
G Gift 36,914 — —
G Gift 36,914 — —
S Open-market sale 2,000 $20.97 $41.9K
Filing: Form 4 (Insider Transaction) Insider: Stepien Thomas M (Director, Chief Executive Officer) Shares: 2,000 Est. Value: $41.9K
View on SEC EDGAR → Open Filing Document →
Proposed Insider Sales 6 · Form 144

A Form 144 is a notice of intent to sell restricted or control securities. It is not a record that anything was sold. Amprius Technologies, Inc. has 6 such notices in this period.

The distinction matters because a Form 144 is frequently reported as though it were a completed insider sale. The filer may sell all of the shares covered, some of them, or none at all, and there is no obligation to update the notice either way. A sale that is actually executed by an officer or director shows up separately on a Form 4, which is the filing to check before treating a proposed sale as a real one.

Form 144 Proposed Insider Sale 2026-08-25

AMPX Form 144 filed for proposed insider sale by KANG SUN (62,101 shares) ~$642.2K

KANG SUN filed a Form 144 with the SEC indicating intent to sell AMPX (Amprius Technologies, Inc.) shares. Form 144 reflects a proposed sale, not a completed transaction. The actual execution, if any, would typically appear later in a Form 4.

Filing: Form 144 (Proposed Sale Notice) Insider: KANG SUN Shares: 62,101 Est. Value: $642.2K
View on SEC EDGAR → Open Filing Document →
Form 144 Proposed Insider Sale 2026-08-25

AMPX Form 144 filed for proposed insider sale by Constantin Ionel Stefan (29,681 shares) ~$306.9K

Constantin Ionel Stefan filed a Form 144 with the SEC indicating intent to sell AMPX (Amprius Technologies, Inc.) shares. Form 144 reflects a proposed sale, not a completed transaction. The actual execution, if any, would typically appear later in a Form 4.

Filing: Form 144 (Proposed Sale Notice) Insider: Constantin Ionel Stefan Shares: 29,681 Est. Value: $306.9K
View on SEC EDGAR → Open Filing Document →
Form 144 Proposed Insider Sale 2026-08-25

AMPX Form 144 filed for proposed insider sale by THOMAS M STEPIEN (23,529 shares) ~$243.3K

THOMAS M STEPIEN filed a Form 144 with the SEC indicating intent to sell AMPX (Amprius Technologies, Inc.) shares. Form 144 reflects a proposed sale, not a completed transaction. The actual execution, if any, would typically appear later in a Form 4.

Filing: Form 144 (Proposed Sale Notice) Insider: THOMAS M STEPIEN Shares: 23,529 Est. Value: $243.3K
View on SEC EDGAR → Open Filing Document →
Form 144 Proposed Insider Sale 2026-08-24

AMPX Form 144 filed for proposed insider sale by THOMAS M STEPIEN (8,000 shares) ~$80.2K

THOMAS M STEPIEN filed a Form 144 with the SEC indicating intent to sell AMPX (Amprius Technologies, Inc.) shares. Form 144 reflects a proposed sale, not a completed transaction. The actual execution, if any, would typically appear later in a Form 4.

Filing: Form 144 (Proposed Sale Notice) Insider: THOMAS M STEPIEN Shares: 8,000 Est. Value: $80.2K
View on SEC EDGAR → Open Filing Document →
Form 144 Proposed Insider Sale 2026-06-08

AMPX Form 144 filed for proposed insider sale by DIXON DONALD R (125,000 shares) ~$2.36M

DIXON DONALD R filed a Form 144 with the SEC indicating intent to sell AMPX (Amprius Technologies, Inc.) shares. Form 144 reflects a proposed sale, not a completed transaction. The actual execution, if any, would typically appear later in a Form 4.

Filing: Form 144 (Proposed Sale Notice) Insider: DIXON DONALD R Shares: 125,000 Est. Value: $2.36M
View on SEC EDGAR → Open Filing Document →
Form 144 Proposed Insider Sale 2026-06-04

AMPX Form 144 filed for proposed insider sale by THOMAS M STEPIEN (2,000 shares) ~$41.9K

THOMAS M STEPIEN filed a Form 144 with the SEC indicating intent to sell AMPX (Amprius Technologies, Inc.) shares. Form 144 reflects a proposed sale, not a completed transaction. The actual execution, if any, would typically appear later in a Form 4.

Filing: Form 144 (Proposed Sale Notice) Insider: THOMAS M STEPIEN Shares: 2,000 Est. Value: $41.9K
View on SEC EDGAR → Open Filing Document →
Material Events 4 · Form 8-K

An 8-K reports a material event in the window between scheduled reports. There are 4 in this period for Amprius Technologies, Inc. Each 8-K names the item number it is filed under, and that number is the fastest way to tell a routine disclosure from a consequential one.

Item 2.02 is an earnings release, Item 5.02 is a change of directors or officers, and Item 1.01 or 2.01 covers a material agreement or a completed acquisition. Item 7.01 and Item 8.01 are the general-purpose disclosure items and carry no fixed meaning on their own.

Form 8-K Material Company Update 2026-09-28

AMPX filed 8-K — material company event

Amprius Technologies, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)
View on SEC EDGAR → Open Filing Document →
Form 8-K Material Company Update 2026-08-13

AMPX filed 8-K — material company event

Amprius Technologies, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)
View on SEC EDGAR → Open Filing Document →
Form 8-K Material Company Update 2026-08-04

AMPX filed 8-K — material company event

Amprius Technologies, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)
View on SEC EDGAR → Open Filing Document →
Form 8-K Material Company Update 2026-06-17

AMPX filed 8-K — material company event

Amprius Technologies, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)
View on SEC EDGAR → Open Filing Document →
Periodic Reports 1 · Forms 10-K and 10-Q

The periodic reports are where the audited and reviewed financial statements live. This period contains 1 quarterly report (10-Q) for Amprius Technologies, Inc.

The two are not equivalent in weight. A 10-K is audited by an external firm and includes the full risk factor disclosure, business description and management discussion; a 10-Q is unaudited, reviewed rather than examined, and much shorter. When a figure in a quarterly report is later revised, the annual report is usually where the correction appears.

An amended report — 10-K/A or 10-Q/A — restates or corrects something in the original filing, and is worth reading against the version it replaces.

Form 10-Q Quarterly Report 2026-08-06

AMPX filed Quarterly Report (10-Q)

Amprius Technologies, Inc. filed its quarterly report with the SEC. This report includes unaudited financial statements and management discussion for the quarter.

Filing: 10-Q (Quarterly Report)
View on SEC EDGAR → Open Filing Document →

How we classify Amprius Technologies, Inc.'s filings

Straight from EDGAR

Each displayed record links to an original source document. StrongBuyAnalytics provides navigation and brief excerpts or summaries, not the filing itself. Parsing may omit context or contain errors, so read the original document in full.

Transaction codes, not guesswork

The nature shown on each insider filing comes from the transaction code the filer entered on the form itself — P for an open-market purchase, A for a compensation award, F for shares withheld to pay tax, M for an option exercise. Where one filing contains several codes, the transaction table lists them line by line.

Why the distinction matters

Insider activity is routinely summarised as buying or selling, which flattens together decisions that mean very different things. Shares withheld for tax on a vesting grant are an automatic administrative step; shares bought on the open market are someone committing their own money at the current price.

What this page does not tell you

A filing records what happened, not why. Form 4 does not always disclose whether a sale was executed under a pre-arranged Rule 10b5-1 plan, and no single filing is a basis for a decision on AMPX. Read these alongside the fundamentals rather than in isolation.

Frequently Asked Questions — AMPX SEC Filings

More Tools for AMPX

AMPX Full Stock Analysis AMPX Live Chart Institutional Ownership Earnings Calendar Options Flow Scanner Semiconductor Demand Zone Tracker Sector Scanner Browse All Stocks

Want deeper AMPX analysis?

View valuation, growth metrics, the rule-based stock-page score, demand zones, peer comparison, and more — all on the AMPX stock analysis page.

AMPX Full Analysis
Publisher, sources & limitations — September 15, 2026. StrongBuyAnalytics provides navigation and brief excerpts or summaries for educational use. Original filings remain at SEC EDGAR or other displayed source links; StrongBuyAnalytics does not author them. Filing dates are source dates, not publication dates for this page. Coverage can be delayed, incomplete, amended, or unavailable because of SEC/source availability, parsing, caching, or outages. Verify every material statement in the original filing.
Data Sources · Methodology · AI Disclosure · Corrections Policy · Disclaimer