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Use only the OEM charger. Never charge unattended overnight. Never charge near flammable materials, hot batteries, or damaged packs. Store long-term at 40-60% charge in a cool dry place. The right charging zone is a garage, balcony, or fire-resistant utility area — never a bedroom or exit path.
6-second explainer
The subject in pictures
By the numbers
Unit: %
Source: FDNY incident analysis, 2022-2024 (n=611)
The full report
1. OEM charger only. 2. Daylight charging, attended. 3. Never near flammable materials or in an exit path. 4. Never charge a hot or visibly damaged battery. 5. Stop at 80% for daily use — only top to 100% when you genuinely need the full range.
These five rules, applied consistently, eliminate the conditions behind well over 90% of fires investigated by FDNY since 2021.
Never charge below 32°F (0°C). Lithium plating on the anode is the failure mode — it permanently degrades the cell and dramatically increases fire risk on subsequent charges. Bring a cold battery to room temperature before charging.
Never charge above ~104°F (40°C) ambient. In summer in a hot garage, wait until evening when the garage cools. Charging a hot battery accelerates degradation and edges closer to thermal runaway thresholds.
Storing a battery at 100% charge for months ages it faster. Storing at 0% can cause irreversible cell damage. The sweet spot is 40-60% state of charge in a cool, dry location (50-70°F). Top off to 40-60% every 3 months if storing for a season.
If a stored battery has been below freezing, warm it slowly to room temperature before charging — overnight is fine. Don't shortcut this; charging too quickly out of cold storage is a known fire-causation pattern.
Authoritative sources