When a child swallows a battery, it's a race against the clock to diagnose and remove the device before it breaks down inside the body within two hours.
Every year, about 20 children are injured so severely after swallowing batteries that they're admitted to Starship hospital.
Health professionals have renewed warnings to parents about the dangers of batteries after the death of a 4-year-old girl in Queensland who suffered stomach bleeding from swallowing a lithium battery.
"Get children to a hospital as quickly as possible and let the doctors know they could have swallowed a battery. Insist that they investigate," said Ann Weaver, Safe Kids New Zealand director.
"We don't have the luxury of waiting for it to pass because it's a two-hour timeframe before it actually starts to cause damage."
Detecting that a child has swallowed or inserted a battery is difficult for doctors because it can look like a button or a coin in an x-ray, so Ms Weaver said it was vital that parents let medical professionals know it could be a battery.
Children should be taken to a hospital rather than a GP or an A&E, and should not eat or drink.
On Sunday, a 4-year-old Sunshine Coast girl died from stomach bleeding after swallowing a lithium button-shaped battery that morning.
Susan Teerds from Kidsafe Queensland said when a child swallowed a battery it often got caught in the oesophagus, around the voice box, and would start to burn a hole after an hour.
"The saliva starts a chemical reaction and burns a hole through the oesophagus and can keep burning a hole into the aorta, through to the spine and whatever else is there."
Toys usually had features to stop children getting at the power source, Ms Weaver said. Television remotes, key-rings and musical cards were devices most likely to pose danger.
Manufacturers have been investigating ways to make batteries safer, including coating them with a blue dye that would be released on contact with saliva, making the electrical current harder to set off, and designing the batteries so they were harder to swallow.
How to keep your child safe
*Ensure devices with battery compartments are secure.
*Keep coin-sized button batteries out of reach.
*Dispose of old batteries.