By Kevin Howlette

Lithium ion batteries are now central to modern workplaces, powering tools, vehicles, equipment, devices and storage systems across every industry. While these batteries are typically safe when used and stored correctly, winter conditions significantly increase the likelihood of battery instability and failure, particularly thermal runaway.

At EHS International, our battery safety consultancy team continues to see a clear seasonal pattern. December and January consistently bring more unstable batteries, more damaged chargers, more temperature related failures and more fire risks that could have been avoided.

Understanding how winter conditions influence lithium ion behaviour is essential for reducing incidents.

1. Cold temperatures increase internal resistance

Lithium ion batteries do not perform well in cold environments. When temperatures drop, the internal resistance of the battery increases. This means the battery must work harder to deliver the same output, resulting in:

  • Slower charging

  • Increased heat generation during charging

  • Reduced efficiency

  • A higher likelihood of cell imbalance

When a battery generates heat internally while surrounded by cold air, the temperature differential places additional stress on the cells. This makes winter one of the highest risk periods for battery instability.

2. Charging cold batteries significantly increases failure risk

One of the most common causes of winter battery incidents is charging cold batteries immediately after they are brought indoors from a cold environment, often without workers realising the risk.

Charging should never begin until the battery has reached a safe ambient temperature.

Charging cold batteries can lead to:

  • Lithium plating

  • Reduced battery lifecycle

  • Internal short circuits

  • Thermal runaway

This behaviour frequently occurs when workers are under pressure to restart tools quickly. Clear procedures, education and visible signage are essential controls.

3. Battery casings become more brittle in winter

Cold temperatures reduce the flexibility of battery casings, making them more vulnerable to physical damage. Drops, impacts or pressure that might normally result in cosmetic damage can cause serious internal cell compromise during winter.

Damaged batteries must never be used. They require immediate quarantine in a designated, fire resistant container away from occupied areas.

4. Storage risks increase during shutdown periods

During holiday closures or reduced staffing periods, batteries are often:

  • Stored fully charged

  • Left connected to chargers

  • Stored in unheated or damp areas

  • Placed too close together

  • Not checked for swelling, impact damage or early warning signs

Cold, unmonitored storage conditions significantly increase internal cell stress and delay detection if a failure occurs.

A growing concern is the use of roof voids as informal storage areas. Industry data shows that approximately 25 percent of workplace fires are linked to roof voids. Limited detection, delayed response and concealed fire spread make storing batteries or battery powered equipment in roof voids particularly dangerous and should be strictly prohibited.

5. Rushed charging and unsafe practices increase in winter

Winter work patterns, reduced daylight hours and productivity pressures often lead to rushed charging practices.

This commonly results in:

  • Overloaded charging stations

  • Mixing incompatible chargers

  • Charging in unsafe or unventilated locations

  • Use of damaged chargers or cables

  • Ignoring early warning signs such as heat, odour or swelling

Rushing is one of the strongest predictors of winter battery incidents.

This risk is further compounded in workplaces with electric vehicle charging. EV charging systems must be properly assessed and certified. Home or vehicle supplied chargers are typically designed for slow charging only and may not be suitable for workplace fast charging units. Using uncertified or incompatible chargers significantly increases fire risk and must not be permitted without formal approval.

6. Fire Warden awareness remains a critical gap

Despite the growing prevalence of lithium ion batteries, very few Fire Wardens are currently trained to recognise battery specific fire risks.

Recent surveys highlight the scale of the issue:

  • Over half of businesses reported an incident involving lithium ion batteries at work, including overheating, smoking or sparking

  • Approximately 19 percent reported actual fires or explosions linked to lithium ion batteries

This demonstrates a significant competency gap within existing fire safety arrangements, particularly during higher risk winter months.

Creating a winter lithium ion safety plan

Managing battery risk in winter requires simple but consistently applied controls:

  • Allow batteries to reach room temperature before charging

  • Never store batteries in cold, damp, roof void or unmonitored spaces

  • Increase inspections of chargers, cables and charging areas

  • Use only manufacturer approved and certified charging equipment

  • Provide designated charging areas with separation and ventilation

  • Implement a clear quarantine process for suspect or damaged batteries

  • Train workers and Fire Wardens on early warning signs of battery failure and thermal runaway

At EHS International, we support organisations to develop seasonal battery safety strategies and deliver targeted training that gives workers and Fire Wardens the confidence to manage unstable or damaged batteries correctly.

Winter does not cause battery failures. It magnifies weaknesses. Strong controls prevent fires.