Stihl AS 2 Battery 5-Pin Pinout for GTA 26, HSA 26, SEA 20 – Functions and Identification

User question

what is the stihl AS2 battery pinout (5 pins) ?

Artificial Intelligence Response

Direct answer to the question

• There is no officially published 5‑pin pinout for the Stihl AS 2 battery in Stihl’s public manuals and product pages. Stihl documents voltage, energy, and charger compatibility, but not the individual terminal functions. (stihlusa.com)
• Based on reverse‑engineering of similar tool packs and standard practice, the 5 terminals are very likely:
  • B+ (main positive)
  • B− (main negative)
  • NTC (temperature sense, typically an NTC thermistor)
  • DATA/COMM (one‑wire or proprietary low‑speed communication)
  • ID/WAKE (battery identification and/or wake/enable)
• Exact pin positions can vary by revision; verify on your pack before use.

Detailed problem analysis

• System context:
  • AS 2 is the 10.8 V nominal battery for the AS‑System tools (e.g., GTA 26, HSA 26, SEA 20), energy ≈28 Wh. These facts are documented; pinouts are not. (stihl.de)
  • Tool batteries with multi‑pin blocks typically split functions into high‑current power rails (B+, B−) and low‑current control rails (NTC, ID, COMM) so chargers can validate pack type/temperature and negotiate charge. Stihl’s AL 1/AL 5/AL 5‑2 pages discuss diagnostics/charging behavior but do not publish pin assignments, indicating the interface is intended as proprietary. (stihlusa.com)
• Likely electrical makeup:
  • Cell topology is almost certainly 3S Li‑ion (10.8 V nominal; ~12.6 V fully charged, ~9 V protection cutoff typical for 3S). This aligns with the stated nominal voltage and common design practice for 10.8/12 V class packs.
  • One small pin is typically an NTC referenced to B− (often ~10 kΩ at 25 °C in many packs); remaining small pins are commonly an ID resistor/line and a data/wake line used by both tool and charger. This arrangement lets the charger refuse charging if temperature is out of range or if the pack is not recognized.
• Why the exact pinout isn’t public:
  • Stihl’s public AS‑System documentation lists performance, charge times, compatible chargers, and environmental ratings, but provides no terminal map. That omission persists on current (2024–2025) product pages, suggesting the pin map is considered service‑level or proprietary. (stihlusa.com)

Current information and trends

• As of November 2025, Stihl has expanded AS‑System charging options (AL 5, AL 5‑2), added on‑board charger diagnostics, and continues to publish charge times and specs—still without terminal‑level pinouts. (stihlusa.com)
• Public retail pages consistently cite AS 2 as 10.8 V, ≈28 Wh, but none include a pin map. (lumberbarn.com)

Supporting explanations and details

• What each pin does (most probable):
  • B+ / B−: High‑current rails feeding the tool; also used by the charger after a “handshake.”
  • NTC: Lets charger/tool ensure safe charge/discharge temperature.
  • DATA/COMM: Proprietary one‑wire or UART/LIN‑like signaling for SoC/SoH, fault, enable.
  • ID/WAKE: Pull‑state or coded ID; may be used to wake the BMS from low‑power and to authenticate the pack.
• Orientation caution:
  • Do not assume “outer two pins are power” without measurement. Different connector geometries and revisions exist; confirm with a DMM on your specific pack.

Ethical and legal aspects

• Miswiring or bypassing the BMS can cause thermal runaway. Only work on Li‑ion packs with appropriate PPE, isolation, and current‑limited supplies. Follow local hazardous‑battery handling and transport regulations.

Practical guidelines

• Safe, non‑destructive identification procedure (suggested):
  1. Visual/physical inspection: Identify which contacts are physically larger or have heavier busbars; these are usually B+ and B− (but still verify).
  2. DMM voltage check:
     • Set meter to DC volts.
     • Probe pairs until you read pack voltage (~8.5–12.6 V for a 3S Li‑ion); mark those as tentative B+ and B−.
  3. Thermistor find:
     • With meter in resistance mode, measure from each remaining small pin to B−.
     • An NTC typically reads a few to tens of kΩ at room temp and changes with gentle warming/cooling.
  4. Data/ID identification:
     • The remaining one or two small pins will not present stable resistance; with the battery on the OEM charger or tool, observe with an oscilloscope (high‑impedance probe). Expect low‑voltage signaling relative to B−.
  5. Never inject external voltage into the small pins. Only measure passively.
• If you need a reliable interface for a project:
  • Salvage the mating connector and small daughterboard from a donor tool or charger so the OEM signals are preserved.
  • Keep the BMS in the loop; avoid direct cell charging.

Possible disclaimers or additional notes

• Model/revision variance: Stihl may revise the BMS/connector behavior without notice; confirm on the exact AS 2 you have.
• Pin naming here reflects industry convention, not Stihl’s internal naming.

Suggestions for further research

• If you can share a clear, in‑focus photo of your AS 2 terminal block (straight‑on, with a reference to orientation), I can help you map pins precisely with guided measurements.
• Community venues like EEVblog/All About Circuits occasionally post reverse‑engineering traces; corroborate any claims with your own measurements before applying power.

Brief summary

• Stihl does not publish the AS 2 five‑pin terminal map; available, current documentation covers only voltage/energy/chargers and omits pin assignments. The most probable functions are B+, B−, NTC, DATA/COMM, and ID/WAKE, but you must verify positions on your pack with a meter/scope before use. If you provide a photo and your goal (repair, adapter, custom power), I can walk you through a safe, step‑by‑step pin identification. (stihlusa.com)

Correction to some sample information you may have seen: the AS 2 belongs to the 10.8 V AS‑System, not the AK battery family; Stihl’s own pages confirm its AS‑System classification and 10.8 V rating. (stihl.de)

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.