Lithium-ion batteries can be EXTREMELY DANGEROUS if mishandled. They can catch fire, explode, or release toxic fumes.
DO NOT proceed unless you understand and accept these risks.
If you are uncomfortable with battery safety or unsure of any procedure, DO NOT BUILD OR USE THIS KIT.
¶ Fire and Explosion Risk
Lithium-ion batteries can experience thermal runaway, resulting in:
- Intense fire that is difficult to extinguish
- Explosion with projectile fragments
- Release of toxic, flammable gases
- Temperatures exceeding TODO °C
- Overcharging: Exceeding maximum voltage (typically TODO V per cell)
- Over-discharging: Dropping below minimum voltage (typically TODO V per cell)
- Excessive current: Charging or discharging too rapidly
- Physical damage: Puncture, crushing, or deformation
- Short circuit: Direct connection of positive and negative terminals
- High temperature: Exposure to heat sources or poor ventilation
- Manufacturing defects: Low-quality or counterfeit batteries
✓ Use ONLY batteries meeting specifications in BOM
✓ Purchase from reputable suppliers
✓ Verify battery specifications before use
✓ Check for physical damage before installation
✗ Never use:
- Damaged, swollen, or leaking batteries
- Batteries of unknown specification
- Batteries exceeding rated capacity
- Counterfeit batteries
- Batteries with damaged protection circuits
✓ Charge in fireproof container or on non-flammable surface
✓ Charge in well-ventilated area
✓ Monitor battery during initial charge cycles
✓ Never leave charging battery completely unattended for extended periods
✓ Keep fire extinguisher nearby (Class D or ABC rated)
✓ Charge at room temperature (TODO to TODO °C)
✓ Stop charging if battery becomes hot (>TODO °C)
✗ Never:
- Charge batteries faster than rated charge rate
- Charge in enclosed space without ventilation
- Charge near flammable materials
- Charge damaged batteries
- Exceed maximum charge voltage (TODO V per cell)
- Leave charging overnight without monitoring
✓ Monitor battery temperature during discharge
✓ Disconnect if battery becomes hot
✓ Respect maximum discharge current
✓ Stop using if voltage drops below minimum (TODO V per cell)
✗ Never:
- Short circuit battery terminals
- Expose to high temperatures
- Discharge below minimum voltage
- Exceed maximum discharge current
- Use damaged batteries
✓ Store at partial charge (TODO% to TODO%)
✓ Store in cool, dry location (TODO to TODO °C)
✓ Store in fireproof container
✓ Keep away from metal objects
✓ Inspect regularly for swelling or damage
✗ Never:
- Store fully charged for extended periods
- Store in hot locations (>TODO °C)
- Store with exposed terminals
- Store damaged batteries with good ones
- Do not dispose of lithium-ion batteries in regular trash
- Take to designated battery recycling facility
- Discharge to storage voltage before disposal (TODO V per cell)
- Tape over terminals to prevent short circuit
- Follow local regulations for battery disposal
- Evacuate immediately if fire spreads or you cannot control it
- Use Class D or ABC fire extinguisher
- Water can be used in large quantities (floods battery, cools fire)
- DO NOT use small amounts of water
- Expect multiple reignitions - battery may continue burning
- Allow battery to burn out in controlled area if safe to do so
- Call emergency services (fire department)
Note: Lithium battery fires are difficult to extinguish and may reignite multiple times.
- STOP using immediately
- Do not charge or discharge
- Place in fireproof container
- Move to safe, outdoor location if possible
- Monitor for signs of thermal runaway
- Dispose of properly at recycling facility
- DO NOT touch electrolyte
- Wear protective gloves and eyewear
- Place battery in sealed plastic bag
- Dispose of immediately at hazardous waste facility
- Wash any contacted skin with soap and water
- Seek medical attention if electrolyte contacts eyes or ingested
- Immediately disconnect from charger
- Move to fireproof container
- Take to safe, outdoor location
- Monitor for fire
- Allow to cool
- Do not reuse - dispose of properly
- Verify correct voltage and polarity before connecting
- USB-C Charging (J2): Use only 5V USB power sources
- Standard USB ports (computer, wall adapter)
- USB-C to USB-C cables with 5V power delivery
- DO NOT use higher voltage USB-PD sources without verification
- Alternative Power Input (J5): Verify voltage rating (TODO V)
- CRITICAL: Reversed polarity can cause immediate battery damage and fire risk
⚠️ WARNING: Test circuit WITHOUT battery first
- Perform initial testing without battery connected (J3 disconnected)
- Verify all voltages at test points:
- Vcc should read expected voltage
- GND should be common ground
- Vb should read 0V with no battery connected
- Use multimeter to measure battery voltage before connection
- Triple-check battery polarity before connecting to J3 (BAT+)
- Be prepared to quickly disconnect power if:
- Any component gets excessively hot
- You smell burning
- LEDs don't illuminate as expected
- Voltage readings are incorrect
Critical Connections:
J3 (BAT+ Connector) - MOST CRITICAL:
- Battery positive and negative MUST be correct
- JST connector is keyed but always verify orientation
- Check polarity THREE times before connecting:
- Verify battery voltage and polarity with multimeter
- Check board markings for J3 polarity
- Verify cable/connector orientation matches markings
- A mistake here can cause immediate fire or explosion
J1 (PWR_OUT) - Power Output:
- Ensure load device can accept 5V input
- Do not exceed maximum current rating (TODO mA)
- Do not short circuit output
J2 (USB-C) - Charging Input:
- Use only 5V USB power
- Ensure cable is in good condition
- Do not force connector insertion
J5 (PWR_IN) - Alternative Power Input:
- Verify voltage rating before connecting
- Check polarity markings
J7 (Vb) - Battery Voltage Output:
- Provides raw battery voltage
- Do not short circuit
- Connected device must handle battery voltage range
Note: Your board's switch configuration is customizable:
- Some boards have SW4/SW5 on top (surface mount)
- Some boards have SW2/SW3 on bottom (through-hole)
- Some boards have no switches (always-on)
Switch Operation:
- Verify which switches control which functions for your configuration
- Press switches gently but firmly
- Do not force or pry switches
- Switches labeled ON/OFF on silkscreen (verify for your board)
- Typical functions:
- ON switch: Enables output
- OFF switch: Disables charging/output
- Ensure all JST connectors are fully seated (click into place)
- Use wire gauge appropriate for current (TODO AWG minimum)
- Never allow battery terminals to touch each other or metal objects
- Clearly label positive and negative on all cables
- Inspect connectors regularly for damage:
- Bent pins
- Cracked housings
- Worn locking tabs
- Discoloration (indicates overheating)
Normal Operating Temperatures:
- Inductor (L1): Warm to touch under load (< 60°C) is normal
- Boost IC (U3): Warm under load (< 70°C) is normal
- BMS ICs (U1, U2): Should remain cool to warm (< 50°C)
- Transistors (Q1-Q5): Cool to warm
- Battery: Should remain cool (< 40°C)
Excessive Heat Indicators:
- Any component too hot to touch (> 80°C)
- Battery temperature > 45°C
- Smell of burning electronics
- Discoloration of components or PCB
If Overheating Occurs:
- Immediately disconnect all power and battery
- Allow to cool in safe location
- Do not reconnect until cause is identified
- Refer to Troubleshooting
¶ Board Handling
- Hold by edges to avoid:
- Shorting components with fingers
- ESD damage to ICs
- Accidental contact with hot components
- Mounting: Use mounting holes H1 and H2 with insulated standoffs
- Ensure board cannot shift and short against metal objects
- Keep away from conductive materials
- Store in ESD-safe bag when not in use
Test Points (Vcc, GND, Vb):
- Use only when measuring with multimeter
- Do not short test points together
- Do not connect external loads directly to test points
- Probes should have insulated leads
- Hold probes carefully to avoid slipping and shorting
ICs on this board are ESD-sensitive:
- BMS chips (U1, U2)
- Boost converter IC (U3)
- Transistors (Q1-Q5)
Protection Measures:
- Use ESD wrist strap connected to earth ground
- Store board in ESD-safe packaging
- Touch grounded metal object before handling board
- Work on ESD-safe mat if available
- Avoid synthetic clothing and carpets
- Ensure adequate ventilation during operation
- Charge batteries in well-ventilated area
- If battery vents gases, evacuate area immediately
- Operate within specified temperature range (TODO to TODO °C)
- Avoid direct sunlight on batteries
- Ensure adequate cooling during high-current operation
¶ Legal and Regulatory
- TODO: CE marking requirements
- TODO: Safety certifications
- TODO: Regional battery regulations
- This device may not meet all regulatory requirements for commercial use
- Intended for educational/hobbyist use only
- You are solely responsible for safe construction and operation
- Follow all local laws and regulations regarding lithium-ion batteries
- UnderBaked is not liable for damage, injury, or fire resulting from use of this kit
- Multimeter (accurate voltage measurement)
- Fire extinguisher (Class D or ABC)
- Fireproof charging container
- Safety glasses
- Well-ventilated workspace
- Smoke detector
- Battery temperature monitor
- ESD wrist strap
- Insulated tools
- Disconnect power before touching victim
- Call emergency services
- Begin CPR if qualified and necessary
- Eyes: Flush immediately with water for 15 minutes, seek immediate medical attention
- Skin: Wash thoroughly with soap and water
- Ingestion: Do not induce vomiting, drink water, seek immediate medical attention
- Inhalation: Move to fresh air, seek medical attention if breathing difficulty
- Disconnect power before touching victim
- Call emergency services
- Begin CPR if qualified and necessary
- Emergency Services: TODO
- Poison Control: TODO
- Fire Department: TODO
- Inspect battery regularly for damage or swelling
- Monitor charging performance over time
- Replace batteries showing degradation
- Keep safety equipment accessible
- Stay informed about battery safety best practices
By building and using this kit, you acknowledge understanding these safety requirements and accept all associated risks.
If you have ANY doubts about safety, do not proceed.
Last Updated: TODO
Revision: See Revision Notes