It seems harmless but a cellphone battery not stored or packed properly could cause a fire during a flight and, in the worst case, a crash.
Such incidents, though rare, are a cause for concern for the aviation industry, given growing flight and passenger numbers.
To mitigate the risks, the Civil Aviation Authority of Singapore (CAAS) is stepping up its public education programme.
Apart from lithium batteries that power cellphones, laptops and other gadgets, the focus is also on other potentially dangerous items such as make-up and perfumes.
In June last year, the CAAS printed and distributed 1.3 million brochures to homes islandwide to explain the dos and don'ts.
A second run will be done later this year, according to its director for airworthiness and flight operations, Mr Tan Kah Han.
The rules state that passengers must not check in lithium-ion batteries unless they are contained within personal devices such as laptop computers and mobile phones. Spare batteries can be carried only in hand luggage. For liquids, gels and aerosols such as perfumes and hair spray, travellers are allowed to hand carry only if the items are placed in containers of less than 100ml. Anything more must be checked in.
Mr Tan said there is worry that travellers may not be aware of items that are classified as dangerous - even everyday ones: "The items do not look like a big threat but make-up and lithium batteries are flammable and when you take them on board and they catch fire, it's a concern for everyone."
To reduce the risk of on-board fires, the International Civil Aviation Organisation banned cargo shipments of lithium-ion batteries from passenger aircraft with effect from April 1 this year. The United Nations agency's precautionary step comes after years of industry concerns that lithium-ion batteries could fuel undetected fires in planes' cargo holds.
The CAAS will continue not just to educate the public, but also to work with shippers, ground handlers and airlines to ensure that potentially dangerous goods are stored and transported according to guidelines.
If necessary, offenders will be taken to task, Mr Tan said. This year alone, the CAAS has investigated nine offences, compared with 18 in total during 2014 and last year.