Charging a modern, undamaged phone or laptop overnight is generally acceptable when you use compatible equipment on a hard, uncovered and well-ventilated surface. Do not charge any device under bedding, pillows or clothing. Larger lithium-ion battery products, including e-bikes, e-scooters and removable power-tool packs, need more caution: stay present while they charge, and never charge them while sleeping.
The answer depends on what you are charging
Lithium-ion batteries vary widely in size, design and the energy they store. Safety depends less on the number of hours connected to power than on the battery’s condition, charger compatibility, temperature, ventilation and whether someone can notice a problem.
| Device | Overnight charging | Safer approach |
|---|---|---|
| Phone or tablet | Generally acceptable if the device, cable and charger are undamaged and compatible | Charge on a hard, uncovered surface with ventilation; keep it away from bedding |
| Laptop | Usually acceptable with compatible equipment and adequate airflow | Use a desk or table, not a bed, couch, carpet or bag |
| Power-tool battery | Best avoided while asleep or away from home | Charge while present, using the charger made for that battery system |
| E-bike or e-scooter | Do not charge overnight or unattended | Stay present, use the supplied or approved charger, and keep exits clear |
Phones and tablets: Many current devices manage charging as the battery fills, and some offer features intended to reduce the time spent at a full charge. For example, some iPhones can pause at 80 percent and complete charging closer to the time you usually unplug. These features can help battery longevity, but they do not make a damaged device, unsuitable charger or heat-trapping surface safe.
Use the cable and adapter supplied with the device, or a compatible replacement that meets applicable safety standards. Do not use a charging cable or adapter with exposed wires, bent plugs, loose connections or signs of overheating. Wireless chargers also need airflow: remove metal objects from the charging surface and use equipment designed for the device. If you use wireless charging, our guide to choosing a Qi2 25W or MagSafe charger for your iPhone explains the practical differences.
Laptops: A laptop and its power adapter can become warm during charging, so leave room for heat to escape. Never charge or operate a laptop inside a bag, under blankets or on a soft surface that can block vents. A laptop’s battery-care or charge-limit setting may help preserve battery capacity, but it does not replace safe placement or sound equipment.
Power-tool packs: Use only the charger specified for the exact battery system. A battery that fits physically may still be electrically incompatible. Do not charge a pack that has been dropped, crushed, punctured, soaked, overheated or otherwise damaged. Charge these larger removable packs while you are awake and nearby, rather than in an empty workshop or overnight.
E-bikes and e-scooters: The United States Consumer Product Safety Commission advises people to be present while charging micromobility products and never charge them while sleeping. Use the charger supplied with the product or a replacement the manufacturer has confirmed is compatible. Do not use a so-called universal charger, a modified battery pack or a repurposed battery.
How to charge lithium ion devices more safely
Fire Prevention Week 2026, held from October 4 through October 10, focused on safe charging habits for lithium-ion products. Its practical advice applies to many devices:
- Use compatible charging equipment. Follow the product manual and use the supplied charger or a manufacturer-approved replacement. Stop using damaged cables, adapters and battery packs.
- Choose a hard, flat surface. A table, desk, workbench or bare floor is preferable to bedding or upholstered furniture. Keep charging equipment away from paper, clothing, curtains, fuels, solvents and other combustible materials.
- Unplug when charging is complete where practical. Do not leave a completed charge connected for long periods without a reason, especially for larger battery products.
- Choose certified products. Buy batteries, chargers and devices from identifiable manufacturers and look for appropriate independent safety certification where it applies. Be wary of unusually cheap, unbranded replacements with no model-specific instructions.
- Check for recalls. Search the Consumer Product Safety Commission recall database by brand and model. Follow the manufacturer’s official remedy rather than continuing to use a recalled product.
These steps reduce the conditions that can lead to thermal runaway, a self-accelerating failure in which a battery cell generates heat faster than it can release it. It can produce intense heat, smoke and flammable gases, and can spread from one cell to others in a battery pack.
Choose the charging location carefully
Beds and couches are unsuitable charging surfaces. Bedding and upholstery can trap heat, obstruct a device’s ventilation and provide fuel if a fire starts. Never sleep on a phone, power adapter or wireless charger, and do not place one under a pillow, blanket or your body.
Keep charging equipment clear and dry. Do not cover a charger or power adapter. Use a sound electrical outlet and avoid damaged power strips, overloaded outlets and daisy-chained extension leads. If an outlet is loose, discoloured, warm or sparking, stop using it and have it assessed by a qualified electrician.
Watch the temperature. The U.S. Fire Administration advises against charging lithium-ion batteries below 32°F (0°C) or above 105°F (40°C). The manufacturer may set a narrower range. An unheated garage may be too cold in winter, and a closed garage may become too hot in summer. Let a battery return naturally to an appropriate temperature; do not warm it beside a heater or leave it in direct sun.
For larger batteries, charge outdoors only when the manufacturer permits it and the location is dry, protected from weather and away from combustible materials. Keep e-bikes, scooters and charging cords from blocking a doorway, stairway or other exit.
Recognize warning signs and dispose of batteries correctly
Stop using or charging a lithium-ion device if you notice excessive heat, swelling, a change in shape or colour, a chemical smell, leakage, smoke, popping or hissing. A swollen phone or laptop battery can push apart the case or make the device sit unevenly. Do not puncture, crush, squeeze or try to repair a swollen battery.
If a battery is damaged but cool and stable, disconnect it from power only if you can do so safely. Keep it away from people and combustible materials, and contact the manufacturer, an authorised repair provider or your local household hazardous-waste programme for handling instructions. Do not recharge it to test whether it still works.
If a device is smoking, rapidly heating, hissing, popping or on fire, leave the area immediately, keep others away and call emergency services from outside. Do not delay evacuation to move the device or retrieve possessions. Working smoke alarms provide important early warning; if yours need replacing, compare hardwired and battery smoke alarms.
Lithium-ion batteries and devices containing them do not belong in household trash or curbside recycling. Take intact batteries to a specialised battery recycler, participating retailer or local household hazardous-waste collection site. For removable batteries, follow the collection site’s instructions; the U.S. Environmental Protection Agency recommends covering terminals with non-conductive tape or placing each battery in a separate plastic bag.
Do not put a swollen, leaking, damaged or recalled battery into an ordinary store collection box. Contact the manufacturer or local household hazardous-waste authority before transporting it, explain its condition and follow its instructions.
Sources
- National Fire Protection Association Fire Prevention Week safe charging guidance
- U.S. Consumer Product Safety Commission micromobility charger safety guidance
- U.S. Fire Administration battery fire safety guidance
- U.S. Environmental Protection Agency lithium-ion battery recycling questions and answers
- Apple iPhone important safety information
