Mouser warns on heatwave risks to phones & chargers

Mouser Electronics has warned consumers not to leave four common gadgets in direct sunlight during the UK heatwave: phones, wireless speakers, wireless headphones and portable chargers.

Prolonged exposure to strong sun can cause overheating, battery damage and, in some cases, create a fire risk. Many modern devices include thermal cut-off systems that switch products off when temperatures rise too far, but users should still move warm devices into the shade or power them down.

Mark Patrick, Director of Technical Content at Mouser Electronics, said the warning was aimed at people spending long periods outdoors during unusually hot weather, whether in parks, gardens or on day trips. The guidance focuses on products commonly carried outside and left exposed while in use.

"With high temperatures across the UK, lots of people will be looking to spend time outside, whether that be having a BBQ, picnic in the park, or going sunbathing. However, it's important not to leave popular tech gadgets such as phones, wireless speakers, portable chargers, or wireless headphones in direct sunlight for too long without risking damaging them, or worse, creating a fire hazard. Although most modern electrical devices usually contain a thermal cut-off to protect cables and devices, meaning the item might automatically turn off if it's getting too hot and then only come back on once it's cooled down, you should still follow steps such as shading the device or turning it off when it feels warm to mitigate these risks," Patrick said.

Phone risks

Smartphones were highlighted as one of the most exposed devices because they are often used continuously outdoors for messaging, calls, photography and streaming. Direct sunlight can push handsets beyond safe operating temperatures, with consequences for both the battery and stored information.

Overheated phones may shut down automatically, interrupting use and increasing the risk of data loss. Users are advised to move a warm phone into a shaded place such as a bag, remove any protective case and either switch the handset off or place it in aeroplane mode until it cools.

Battery strain

Portable wireless speakers were another area of concern. These products typically rely on lithium-ion batteries, which can degrade more quickly when exposed to heat during charging or playback.

Sunlight can add to the heat generated during normal speaker use, reducing the battery's ability to retain charge and causing it to drain faster over time. Mouser also warned that ultraviolet exposure can bleach the outer finish of some speakers, adding cosmetic damage to the risk of shorter battery life.

Consumers are advised to switch speakers off when they are not being used and store them away rather than leaving them on patios, picnic blankets or garden tables. If a speaker remains in use, it should be placed in a shaded area.

Headphones and chargers

Wireless headphones face a different set of issues because, in addition to batteries, they contain compact internal microchips that support functions such as Bluetooth connections. These parts are sensitive to heat exposure and may short-circuit if temperatures rise too high.

Mouser also cautioned against charging overheated headphones immediately after sun exposure. Some batteries will slow or stop charging as they attempt to regulate temperature, so users should allow the product to cool first.

Portable chargers, often carried as backup power on long days out, were identified as another product category with heightened heat sensitivity. Like speakers and phones, many power banks use lithium-ion batteries.

Users should watch for any bulging in the casing of a portable charger if it has been left in direct sun. This can indicate internal heat build-up and may point to permanent damage.

The warning comes as hot weather increases scrutiny of battery safety in everyday consumer electronics. Small portable devices are now widely used outside the home for work, communication and entertainment, but their compact batteries and sealed casings can make them vulnerable when temperatures rise.

For businesses in the electronics supply chain, the advice also reflects a broader issue around how consumers handle products in extreme conditions. Retailers and manufacturers have long relied on automatic shutdown systems and charging controls to reduce harm, but user behaviour still plays a central role in limiting wear, preserving battery health and avoiding failures.

Patrick's advice was simple: "If your phone gets warm, put it in a shaded place like a bag, remove any protective casing, and turn it off or switch to aeroplane mode."