The two worst cases seen by Dr Shepherd were children who had stuck the battery inside their nose.
"They have been up in the nose for a while and no one's really noticed and they've burnt right the way through the middle bit of the nose causing permanent damage."
If the battery makes it to the stomach most children can pass them but larger ones can lodge in the oesophagus and the damage occurs within a couple of hours, Dr Shepherd said.
That could mean long-term problems with swallowing food while the repair itself is painful and can require multiple surgeries.
The rising number of cases has prompted Safekids NZ to create a campaign which it will launch in June aimed at making parents and caregivers aware of the dangers.
Manufacturers were investigating ways to make the 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.
In the meantime Dr Shepherd urged parents to think about what the batteries were in, and how they were stored and disposed of.
"I think they should be stored and treated like a poison."
Lithium batteries were not the only objects Dr Shepherd had seen on x-rays of children's insides.
Other offending household items included open safety pins, magnets and of course children's toys.
"Kids will explore by putting in their mouth and then accidentally swallowing. In terms of up noses and in ears it's usually bits of Lego or beads or little action men."
Dish washing powder and adult prescription pills could also cause serious injury. He said parents did not need to watch small children so vigilantly if they stored household items correctly.
Coin lithium batteries can be found in
• Talking and singing children's books and greeting cards
• Mini remote control devices
• Calculators
• Miniature torches and flameless/electronic candles
• Reading lights
• Bathroom scales
Parents should make sure
• Battery compartments are secure
• Keep coin-sized button batteries out of sight and reach
• If swallowing is suspected, go immediately to A&E or call 0800 POISON (0800 764 766)
Tiny but dangerous coin batteries easily swallowed
Olivia Sweeney keeps coin batteries out of reach of her three young children after 4-year-old Tom swallowed one and had to be rushed to Starship hospital for emergency surgery.
Fortunately the then 3-year-old didn't need the operation to remove the lithium battery after it moved into his intestine. The Whangarei preschooler was instead given medicine to help pass the battery, which he did the next day.
Mrs Sweeney said the incident a few months ago was frightening.
Tom found the tiny battery in a drawer and moments later he had swallowed it.
"He came through and said 'oh I've just' and he pointed to his throat, 'and it's gone down'," Mrs Sweeney said. "I tried to force him to throw up which is the wrong thing to do."
At an accident and emergency department an X-ray showed the battery sitting in Tom's stomach and Mrs Sweeney was advised that her son would have to go to Starship, in Auckland.
"I was freaking out. I thought 'Oh my God'."
The two-hour drive for husband Ian was nerve-racking because it was enough time for the battery to burn Tom's stomach lining.
Fortunately a second x-ray at the hospital showed it had not caused any damage.
Mrs Sweeney advised parents to lock up the batteries or place them out of reach as she now does to protect Tom and her two other children, 6 and 1.
"Parents are probably unaware. They are very dangerous. You just have to teach children not to put things that aren't food in their mouth."
