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Safely Discharge DJI Batteries with Arduino

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User question

Dji batterie killer with arduino

Artificial Intelligence Response

Direct answer to the question

• “DJI Battery Killer” is a community-made script that unlocks / revives DJI smart batteries whose BMS has entered “Permanent-Failure (PF) lock-out” after deep discharge or long storage.
• An Arduino (UNO/Nano/Pro-Micro) can act as a low-cost SMBus / I²C master to send the Texas-Instruments-style commands that un-seal the BMS, clear PF flags and, if required, reset the cycle counter.
• Typical workflow

  1. Bring every cell above the BMS minimum (≈ 3.0 V / cell) with a lab supply or TP4056 boards.
  2. Wire Arduino → battery SDA/SCL/GND (no VBUS!) and upload “battery-killer” sketch.
  3. Run the script: UNSEAL → FULL-ACCESS → CLEAR_PF / RESET_FUSE.
  4. Re-insert the pack in the DJI charger/drone and perform a balanced charge.

Detailed problem analysis

  1. DJI smart-battery architecture
    • 4- to 6-cell Li-Ion/LiPo stack (Mavic: 3 S / 4 S; Inspire: 6 S).
    • Texas-Instruments gas-gauge / BMS (BQ30z55/BQ40z50/BQ900x family).
    • SMBus address 0x0B (Std. Smart-Battery spec).
    • Protection flags: PF, PF2, CUV (under-voltage), OCC (over-current), OT (over-temperature).
    • Once PF is asserted, the FETs are latched open (no charge / discharge). A simple charger will not recover the pack.

  2. Why “battery killer” is a revival, not destruction
    • Community coined name because it “kills” the PF flag, not the cells.
    • Off-line sample answers confuse the term with destructive discharge; those methods are unrelated to the DJI revival tool.

  3. SMBus command sequence (generic) 

    // ManufacturerAccess register = 0x00 on TI gauges
UNSEAL_STEP_1 0x3672
UNSEAL_STEP_2 0xFFFF
FULL_ACCESS 0xFFFF // some gauges need this
CLEAR_PF 0x0015 // or 0x0029 depending on IC
RESET_GAUGE 0x0041 // soft reset (optional)

    TI gauges use little-endian. Always confirm with a register-map dump (MAC = 0x23/0x40 for BQ40z50).
    Important: Different DJI models use slightly different firmware; use a dump from an intact battery of the same type whenever possible.

  4. Arduino wiring & level considerations
    • 5 V Arduinos usually tolerate 3.3 V SMBus pulled up by the battery (safe).
    • Connection:
    – Arduino A4 → SDA
    – Arduino A5 → SCL
    – Common GND
    – Do NOT feed +5 V into the pack!
    • Typical pull-up already present on the BMS; if not, add 4.7 kΩ to 3.3 V.

  5. Minimal sketch (Wire-library) 

    #include <Wire.h>
const byte BMS = 0x0B; // SmartBattery default
void sendCmd(uint16_t cmd){
Wire.beginTransmission(BMS);
Wire.write(lowByte(cmd));
Wire.write(highByte(cmd));
Wire.endTransmission(true);
delay(50);
}
void setup(){
Wire.begin(); Serial.begin(115200);
sendCmd(0x3672); // Unseal 1
sendCmd(0xFFFF); // Unseal 2
sendCmd(0xFFFF); // Full-access (some gauges)
sendCmd(0x0015); // Clear PF
sendCmd(0x0041); // Gauge reset (optional)
Serial.println("Done – disconnect and test in charger.");
}
void loop(){}

    Adapt commands for your exact gauge/firmware (consult TI data-sheet or working dump).

  6. Pre-charging deeply depleted packs
    • DJI BMS powers up only above ~9 V (3 S) / 12 V (4 S).
    • If total pack is lower, open casing, isolate each cell pair, trickle charge at ≤ 0.2 C to 3.6 V / cell, monitor temperature, then re-assemble.
    • After BMS wakes, proceed with the Arduino procedure.

  7. Verification
    • Read SBC commands 0x09 (Voltage), 0x0A (Current), 0x0F (RemainingCapacity).
    • LED bar should respond, charger should accept the pack.
    • Perform a full, balanced charge/discharge cycle and log IR to ensure no cell is damaged.

Current information and trends

• Community keeps repositories on GitHub and GreyArrows / MavicPilots forums (2024 posts confirm procedure works on Mini 2, Air 2, Mavic Pro).
• CP2112 USB–I²C dongle is gaining popularity because scripts run directly from Python GUI; nevertheless, Arduino remains the cheapest platform.
• Newer DJI batteries (Avata, Mini 4) appear to add authentication crypto; the “battery killer” approach may not work without keys – area of active research.

Supporting explanations and details

• Think of the DJI BMS as a “fuse with a microcontroller”. The PF bit is that blown fuse. Clearing it is like sending a software command to re-latch the gate FETs.
• The two-step UNSEAL code acts as a password; FULL-ACCESS escalates to manufacturer level where destructive commands (e.g., flash write) are allowed.

Ethical and legal aspects

• Warranty / TOS: Any manipulation voids DJI warranty; in some regions altering certified battery firmware may infringe regulations.
• Transport safety: A previously PF-locked pack was deemed unsafe. Confirm IR, balance and capacity before flying – otherwise you endanger airspace and property.
• Environmental responsibility: If cells show > 20 mΩ IR or > 30 % imbalance after revival, recycle the pack instead of flying with it.

Practical guidelines

• Work on a ceramic/metal surface, have a class-D (Li-ion) fire extinguisher.
• Use insulated probe clips; accidental short on a 4 S pack can deliver > 80 A.
• Log every SMBus transaction; if gauge NACKs the command, stop and re-evaluate wiring or cell voltage.
• After successful revival, flash the latest DJI firmware to the battery via DJI Fly / Go4; this recalibrates cycle count tables.

Possible disclaimers or additional notes

• Not all PF causes are benign. Packs that locked due to over-temperature or internal resistance rise can fail catastrophically even after reset.
• TI changed unseal passwords on some OEM firmware; brute-forcing is non-trivial and beyond the scope of this guide.
• Future DJI generations may incorporate secure-element based authentication, making this method obsolete.

Suggestions for further research

• Reverse-engineering of crypto-secure gas gauges (TI BQ40z80 with SHA-256).
• Automated cell-level impedance spectroscopy to decide whether a revived pack is flight-worthy.
• Development of an open-source “Smart-Battery-Doctor” combining CP2112 + ADC sampling for all hobby-drone packs.

Brief summary

The so-called “DJI Battery Killer” does not destroy batteries; it is an I²C/SMBus routine that revives DJI smart batteries locked by their BMS. An Arduino can deliver the necessary unseal and PF-clear commands once the pack voltage is high enough for the gauge to power up. The process requires careful pre-charge, correct wiring, and adherence to Li-ion safety practice. Always validate cell health after revival and respect legal responsibilities when flying or disposing of repaired packs.

User question

Clear pf of phantom 3 battery with arduino

Artificial Intelligence Response

Direct answer to the question

  • Yes, you can attempt to clear a DJI Phantom 3 battery’s PF (Permanent Failure) using an Arduino by talking SMBus to the TI fuel gauge inside (bq30z55 family). In practice you must:
    • Wake/power the BMS, access the real SMBus pins (often internal test pads), and use the Smart Battery “ManufacturerAccess” commands to unseal, (optionally) enter full access, issue PF‑clear, reset, then reseal. (laptopu.ro)
  • Success is not guaranteed. Some packs require a device‑specific PF key or show PF again if any cell remains out of bounds; in those cases an Arduino script alone may not clear PF and tools like EV2400/bqStudio or the community “DJI Battery Killer” (CP2112→SMBus) workflow are typically used. (doczz.net)

Key points

  • Identify and use the true SMBus pins (SMBD/SDA, SMBC/SCL, GND) on the Phantom 3 battery PCB; they are not always present on the main battery output connector. (laptopu.ro)
  • Default TI unseal keys are usually 0x0414 then 0x3672; default full‑access keys are 0xFFFF, 0xFFFF; must be sent to ManufacturerAccess (0x00) as two words within 4 s. Vendors may change keys. (e2e.ti.com)
  • “PF Data Reset” (0x0029) only resets PF logs on many TI gauges; some devices require a proprietary PF‑clear key (“PFKey”) to truly re‑arm FETs if Long‑Term PF logging is enabled. (digikey.com)
  • The Phantom 3 pack is a 4S Li‑ion polymer HV battery (15.2 V nominal, ≈17.4 V full). Precharge any deeply discharged cells to a safe level before commanding the BMS. (www-v1.dji.com)

Detailed problem analysis

  • Architecture: Phantom 3 packs integrate a TI bq30z55‑family gauge/protection plus FETs. They speak SBS/SMBus at the standard 7‑bit address 0x0B. SBS standard commands (e.g., Voltage 0x09, Current 0x0A, BatteryStatus 0x16) and the ManufacturerAccess register (0x00) are used for control/diagnostics. (en.wikipedia.org)
  • PF behavior: When a severe undervoltage/imbalance/over‑temp condition is detected, the gauge sets PF, opens CHG/DSG FETs and may log backup data; if “LTPF” logging is configured, a dedicated PF clear key (PFKey) can be required to clear the condition; simply writing “PF Data Reset” clears logs but may not re‑arm FETs. (doczz.net)
  • Unseal/full‑access: For many TI multi‑cell gauges the default unseal words are 0x0414 then 0x3672; full‑access is 0xFFFF twice; both must be written to 0x00 within 4 s, with no intervening commands. If DJI changed keys, your script must use the pack’s programmed values. (e2e.ti.com)
  • Reset: After clearing PF you typically issue a reset (TI gauges accept a “reset” MA subcommand; many designs use 0x0041 on bq40z50 family; exact opcode can differ among TRMs). A reset returns the gauge to SEALED unless you explicitly keep it unsealed. (e2e.ti.com)
  • Access points: On Phantom 3 batteries, SMBus test pads labeled SMBD/SMBC/GND are on the board; external thin pins at the power connector can be UART to the airframe, not SMBus. Use the test pads; if another MCU on the board shares the bus (e.g., MSP430), you may need to keep the battery “awake” or isolate that bus master during service. (laptopu.ro)

Current information and trends

  • Community workflows such as the CP2112‑based “DJI Battery Killer” target DJI packs with TI bq30z55/bq40z50 derivatives and provide PF1/PF2 clear, unseal, reset, stats readout. They are widely reported for Mavic/Spark/Air; the Phantom 3 uses a similar gauge so techniques are transferable, but pinout and keys differ. (elektroda.com)
  • Newer DJI batteries (Mini 3 Pro, Avata 2, etc.) add authenticated firmware/encryption; these are outside the scope of Phantom 3 but explain why tools increasingly use CP2112 + custom software rather than simple I²C scripts. (elektroda.com)

Supporting explanations and details

  • Safe electrical levels:
    • Use a 3.3 V Arduino (e.g., Pro Mini 8 MHz) or a bidirectional level shifter; the pack provides its own SMBus pull‑ups. Avoid enabling Arduino’s internal pull‑ups to 5 V. Bus speed: 100 kHz. (powercartel.com)
  • Cell precharge:
    • If any cell ≲3.0 V, the gauge may sleep and/or refuse PF clear. Carefully precharge cells individually at ≤0.5 A to ≈3.4–3.7 V, monitor temperature, and keep cell delta ≤50 mV before SMBus work. This avoids an immediate re‑PF upon wake. (reddit.com)
  • Which commands to read:
    • Read BatteryStatus (0x16) and, via ManufacturerAccess, SafetyStatus (often 0x0051) and OperationStatus (0x0054) to confirm SS/FAS/PF/LTPF state before and after your sequence. (e2e.ti.com)

Example Arduino sequence (outline, not exhaustive): 1) Wake battery (pack voltage present, button “on,” or light bench supply across PACK+/GND if required).
2) Wire Arduino GND → battery GND; SDA/SCL → SMBD/SMBC test pads.
3) I²C address 0x0B.
4) Unseal: write 0x0414 to 0x00, then 0x3672 to 0x00 within 4 s.
5) Optional: Full access: 0xFFFF, 0xFFFF to 0x00.
6) PF clear attempt:

  • Write 0x0029 to 0x00 (PF Data Reset) and/or the device’s PF clear key if known; then reset (e.g., 0x0041). Verify PF bits cleared and FETs on. Note: on some bq30z/bq30z55 builds, PF Data Reset only clears log; true PF clear requires PFKey. (digikey.com) 7) Reseal (optional) and move immediately to an OEM charger for a supervised, full balance charge.

Minimal C++ helper (conceptual):

  • WriteWord(addr=0x0B, cmd=0x00, data=word)
  • ReadWord(addr=0x0B, cmd=0x16) // BatteryStatus
  • Consider adding SMBus PEC if the gauge requires it; many DJI packs accept no‑PEC writes. (ti2k.com)

Ethical and legal aspects

  • Safety: PF is a safety latch. Clearing it on a pack with damaged cells can create a fire hazard. Only proceed after cell health is verified and in a fire‑safe area. (elektroda.com)
  • Warranty/liability: Any unseal/full‑access operation voids manufacturer warranties and shifts responsibility to you.
  • Transport: Reworked Li‑ion packs may not meet UN 38.3 transport tests; shipping carriers can refuse them.

Practical guidelines

  • Implementation methods:
    • Preferred hardware for TI gauges is EV2300/EV2400 with TI bqStudio (Windows). If you stay with Arduino, validate bus discovery with an I²C scanner first. If the gauge is not at 0x0B, the BMS is asleep or pins are wrong. (e2e.ti.com)
    • If the PF does not clear with 0x0029 + reset, assume PFKey is required; try a CP2112 + “DJI Battery Killer” session that implements additional vendor‑specific sequences. (github.com)
  • Best practices:
    • Keep the pack “on” (button) or provide a limited bench supply so the coprocessor does not hold SMBus lines low.
    • Log before/after: Voltage (0x09), Current (0x0A), cell voltages (0x3F..0x3C), BatteryStatus (0x16), OpStatus (0x0054).
    • After recovery, perform a slow, supervised full charge and several low‑load discharge cycles; retire the pack if IR is high or imbalance persists. (reddit.com)
  • Challenges and mitigation:
    • Hidden pins: open the enclosure to reach SMBD/SMBC; verify with a meter. (laptopu.ro)
    • Multi‑master bus: another MCU can hold SMBus; you may need to keep the battery awake or temporarily isolate that MCU. (laptopu.ro)

Possible disclaimers or additional notes

  • Command codes vary by TRM revision and firmware; don’t assume bq40z50 opcodes map 1:1 to bq30z55. Always verify on your device; misuse can brick the gauge. (e2e.ti.com)
  • Some Phantom 3 packs will never recover (swollen cell, blown fuse, excessive IR). In such cases replacement is the only safe option.

Suggestions for further research

  • TI references:
    • bq30z55/bq3055 technical documentation on PF behavior and PFKey; study Permanent Fail flow and LTPF. (doczz.net)
    • TI E2E forum posts on unseal/full‑access keys and reset behavior for the bq40zxx family (same security model). (e2e.ti.com)
  • Tools:
    • TI bqStudio with EV2400; or CP2112 + “DJI Battery Killer” documentation/workflows for DJI packs. (github.com)

Brief summary

  • Clearing PF on a Phantom 3 battery with Arduino is feasible when the BMS is accessible and cells are healthy: unseal (0x0414, 0x3672), optional full‑access (0xFFFF, 0xFFFF), attempt PF clear (e.g., 0x0029 and/or PFKey), reset, then charge and validate. Expect to open the battery to reach SMBD/SMBC pads, and be prepared to switch to EV2400/bqStudio or CP2112 tooling if the pack requires a PFKey or vendor‑specific unlock. Above all, confirm cell health first and treat PF as a real safety event, not just a nuisance flag. (laptopu.ro)

If you want, I can provide a compact Arduino sketch with optional PEC, plus a step‑by‑step checklist for probing and confirming the Phantom 3 test pads before issuing any commands.

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