EV or hybrid battery swelling, safety concern

Symptoms

• Visible bulging or deformation of a battery pack or its cover
• Unusual smell, hissing sound, or smoke near the battery area
• Battery area feels unusually hot to the touch
• Warning lights combined with any of the above

Likely causes

• PossibleInternal cell failure or thermal eventA failing battery cell can generate excess heat and gas, causing physical swelling, which can escalate quickly.
• PossiblePhysical damage from an impactA significant impact to the underbody or battery area can damage cells internally even without obvious external damage.
• PossibleCharging fault causing overheatingA malfunction during charging can, in rare cases, cause excessive heat buildup in the pack.

What to do

1. Stop driving or charging the vehicle immediately if you notice swelling, an unusual smell, hissing, smoke, or excessive heat from the battery area.
2. Move away from the vehicle to a safe distance; do not attempt to inspect, touch, or cool the battery yourself.
3. Call 911 or your local emergency number if you see smoke, flames, or a strong burning smell.
4. If safe to do so from a distance, notify people nearby and keep them away from the vehicle.
5. Contact the manufacturer's emergency roadside or safety line, since many have specific protocols for battery incidents.
6. Do not attempt to move the vehicle into an enclosed garage if a battery fault is suspected; leave it in an open, safe area if possible.

When to call a pro

This requires immediate attention from emergency services if actively smoking or on fire, and otherwise from the manufacturer or a certified EV service center; do not attempt any DIY inspection or repair.

Safety