Fatal fire in Ang Mo Kio flat sparked by modified PMD batteries left to charge: Coroner

Feb 28, 2024

Singapore

The fire that broke out in the morning of Mar 5, 2021 took the life of a woman whose son had bought a modified personal mobility device online.

The kitchen (left) where SCDF firefighters rescued a man who was trapped in the toilet and the living room (right) of the HDB flat where a fire broke out. (Photos: Singapore Civil Defence Force)

SINGAPORE: A fire in an Ang Mo Kio flat that took the life of a 49-year-old woman originated from lithium-ion cells in battery packs that were left to charge on top of an illegally modified personal mobility device (PMD), a coroner's court has found.

The PMD had been purchased on Carousell by the woman's son the night before the fire that consumed the cluttered contents of the flat.

In a written set of findings made available on Monday (Jul 31), State Coroner Adam Nakhoda ruled the death of Madam Tay Choon Hwee a misadventure.

She had died of smoke inhalation, after being taken to hospital in an unresponsive state on the morning of Mar 5, 2021.

He said this case was "a timely reminder of the inherent dangers posed by modified PMDs" and advised users not to buy such devices or modify stock PMDs.

Users should also only charge their devices with the chargers that come with them, he said.

The court heard that Mdm Tay lived in a flat in Ang Mo Kio with her son, named in the findings only as "Mr Ching".

In early March 2021, Mr Ching saw a PMD listed for sale on Carousell for S$1,500 by a Mr Muhammad Shahrul Abdul Razak.

Mr Shahrul testified that he had obtained the PMD by trading a previous device for it on Carousell. He said his wife told him to buy a smaller one that was "not dangerous", so he listed it for sale.

Mr Shahrul claimed that when he negotiated with Mr Ching over the sale, he had told Mr Ching that the device was not compliant with Land Transport Authority regulations.

They met on the night of Mar 4, 2021, for the transaction. Mr Shahrul gave Mr Ching two 36-volt lithium-ion battery packs but no battery charger. Mr Ching tested the PMD before riding it home.

The PMD was too large to fit into the lift at his Housing Board block initially, and Mr Ching was seen on police camera footage adjusting it.

At about 2am on Mar 5, 2021, he used his own charger to charge the battery packs and monitored it for two hours.

When there were no issues, he joined his mother in their bedroom to sleep at about 4am and left the battery packs charging.

His mother woke him up at about 5am to 6am saying she heard loud noises that sounded like explosions.

They opened the bedroom door and saw a fire around the PMD, with the lithium-ion battery cells "popping", the court heard.

Mr Ching went to the kitchen toilet to get water to extinguish the fire with, but he soon saw thick black smoke entering the kitchen area.

He closed the toilet door, opened the window for fresh air and shouted for help.

A member of the public had called the Singapore Civil Defence Force (SCDF) for help at about 6.10am, and firefighters arrived to see black smoke coming from the unit.

They put out the fire, noting that the living room was full of hoarded items, and found Mr Ching conscious in the toilet.

They found Mdm Tay lying passed out on the floor of the bedroom, which was "heavily smoke logged", with some items on top of her, the coroner said.

SCDF's fire investigation report concluded that the fire damage was consistent with a fire that originated from the battery packs that had been left to charge on the seat of the PMD.

SCDF said an electrical anomaly had likely occurred within the battery packs while they were being charged, leading to thermal runaway.

This is an instability that occurs when heat generation exceeds heat loss within a material, and this leads to a self-sustained smouldering or burning.

"The heat from the thermal runaway most likely caused the lithium-ion battery cells to ignite and some may have been dispersed in all directions, including onto the combustible items that were stored and cluttered in the unit's living room. This would have contributed to the fire spreading in the living room," read SCDF's report.

SCDF added that Mr Ching's battery charger, from his previous PMD, could possibly have been incompatible with the newly bought PMD and its battery packs, resulting in a catastrophic failure of the lithium-ion battery cells.

The coroner said the PMD had been modified such that it was no longer certified for use in Singapore.

He said there was no foul play involved in Mdm Tay's death.