Hilti C4/36-350 charger starts for 2 seconds then stops – MIP2M2, L6599AD, MOSFET, fan, capacitor faults

User question

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Artificial Intelligence Response

Direct answer to the question

• Symptom “starts for ~2 seconds, then stops” on a Hilti C4/36-350 charger is typical of a protection shutdown triggered by a fault in the power/thermal/feedback chain.
• Most frequent hardware culprits reported by repair logs: MIP2M2 auxiliary SMPS IC (and its low‑ohmic resistors), L6599AD resonant controller, primary MOSFETs (12NM50ND/STP12NM50FP), shorted secondary rectifiers/caps, or a failed cooling fan tach signal.
• First isolate whether it shuts down with no battery inserted. If yes, the fault is inside the charger.

Detailed problem analysis

• What the 2-second window means:

  • The input bridge and bulk capacitor charge, the auxiliary flyback (often based on MIP2M2) brings up logic rails, the MCU/fan/self-test runs, then the main LLC stage (L6599AD) tries to start. Any fault (overcurrent, missing fan tach, undervoltage on Vcc, shorted secondary) causes the supervisor to latch off within 1–3 s.

• Fault classes and diagnostics (from least to most invasive):

  1. External/operational checks

     • Try on a known-good outlet and surge strip; avoid long extension leads.
     • Power the charger with no battery. Observe LED pattern and fan:
     • Green LED blinking every ~2 s with self-stop commonly signals protect/standby.
     • Fan that twitches or doesn’t reach speed suggests a tach fault or seized fan.
     • Try with a known-good compatible Hilti Li‑ion pack; if the unit still shuts down, it’s internal.

  2. Thermal/cooling path

     • Dust often stalls the internal fan. If the firmware doesn’t detect RPM within the startup window, it shuts down. Spin the fan gently with a non-conductive stick (unpowered). If sticky, replace/clean. Electrically, check for fan supply during the 2 s (commonly 12 V).

  3. Secondary-side shorts/aging parts

     • Shorted Schottky/synchronous rectifier or output electrolytic with very high ESR can pull the LLC into overcurrent. With power off and discharged, check:
     • Resistance from output rails to ground; near-zero ohms indicates a shorted rectifier.
     • Visual signs: bulged electrolytics on the low‑voltage side.

  4. Primary-side power train

     • Primary MOSFETs (12NM50ND/STP12NM50FP) shorted D‑S or a cracked current-sense shunt will trigger OCP quickly. Check MOSFETs in diode/ohms mode (unit unplugged, caps discharged).
     • If the bulk cap charges but the PFC/LLC never stabilizes, suspect the L6599AD controller or its Vcc rail.

  5. Auxiliary/housekeeping supply (high incidence)

     • The small flyback based on MIP2M2 often fails (sometimes along with several 1 Ω resistors in its start/limit network). Symptom: logic rail rises, then sags; repeated hiccup every ~2 s.
     • Measuring (safely) during the first seconds:
     • DC bus after the bridge: ~160–170 VDC at 120 VAC input (USA), later boosted if active PFC engages.
     • L6599AD Vcc should rise to its UVLO threshold (~11–13 V typical) and stay stable; if it rises then collapses, auxiliary supply is suspect.

• Why these fail:

  • Dust/thermal stress in construction environments accelerates fan and capacitor wear.
  • Repeated surge events stress the auxiliary SMPS IC and its current-limit/start resistors.
  • Load transients during battery attach can expose weak feedback/compensation components.

Current information and trends

• Community repair experience for C4/36-350 shows a high repair rate by replacing:
  • MIP2M2 plus three 1 Ω resistors (common fix on “hiccup every ~2 s” units).
  • In many of those cases, the L6599AD driver also needs replacement.
• Repeated mentions of primary MOSFET failures (12NM50ND/STP12NM50FP) and assorted diodes/feedback parts align with the 2 s protect behavior. These data points come from recent technician forums and repair threads.

Supporting explanations and details

• Architecture overview:
  • Input EMI/bridge → bulk cap → PFC (boosts to ~380–400 VDC once running) → LLC resonant converter (L6599AD) → secondary rectification/filters → battery management/MCU.
  • Auxiliary flyback (MIP2M2) powers logic and the L6599AD Vcc. If this rail hiccups, the main stage never stays latched.
• LED behavior:
  • Slow periodic blink at ~2 s cadence with auto-stop typically indicates the supervisor is retrying or has latched protect. Exact codes vary by firmware revision.

Ethical and legal aspects

• Mains-powered SMPS contain lethal voltages (charged bulk capacitors). Service should be performed by qualified personnel using isolation transformers and proper PPE.
• Opening the charger may void warranty and UL/CE conformity; in the US, follow electrical safety practices and dispose of failed parts as e‑waste.

Practical guidelines

• Non-invasive (owner level):
  • Clean vents; ensure free fan rotation.
  • Test on a different outlet; try with no battery and with a known-good battery.
  • Inspect and clean battery contacts with isopropyl alcohol.
• Bench diagnostics (technician level; unit unplugged, caps discharged):
  • Check fan supply during the 2 s; verify tach line if present.
  • Measure output-side shorts; inspect secondary electrolytics.
  • Test primary MOSFETs for shorts; inspect current-sense shunts.
  • Check auxiliary Vcc stability; if it sags/hiccups, replace MIP2M2 and the low‑ohm resistors; if startup resumes but main stage won’t sustain, evaluate/replace L6599AD.
  • After semiconductor replacement, always check gate resistors, snubbers, and feedback optocouplers; a hidden defect can re-kill new parts.
• After repair:
  • Power up through a series bulb or variac + isolation to limit fault current.
  • Verify no-load stability, fan RPM, then test with an electronic load before trying a battery.

Possible disclaimers or additional notes

• LED code meanings differ by production batch; if you can share the exact blink pattern, we can map it more precisely.
• Some units exhibit intermittent solder joint cracks; thermal rework of heavy components (heatsinks, inductors) may be required.

Suggestions for further research

• Obtain the service notes/schematics or part identifiers on your PCB revision; cross-check controller pin UVLO thresholds and expected waveforms.
• Review community repair threads specific to C4/36-350 for BOM references and successful fixes focused on MIP2M2/L6599AD/fan faults.
• If under warranty, use Hilti service; for out-of-warranty units, board-level repair is feasible with proper tools.

Brief summary

• A 2 s start-then-stop on the C4/36-350 almost always indicates a protection-triggered shutdown. Most common roots: seized/undetected fan, short on secondary/output capacitors, failed auxiliary SMPS (MIP2M2 and nearby 1 Ω resistors), bad L6599AD driver, or shorted primary MOSFETs.
• Start with no-battery test and fan check; if internal, stabilize auxiliary Vcc and verify the LLC controller and power devices before loading.
• If you can, please confirm: exact model, LED pattern, whether the fan spins, and whether the behavior occurs with no battery attached. With that, I can tailor exact test points and parts for your PCB revision.

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.