A food delivery rider suffered severe burns to his body after his electric bike caught fire while charging in a bedroom.
The blaze, which took place last week at a flat in Highgate, north London, was extinguished by firefighters.
But the man suffered serious burns to several parts of his body while trying to put out the fire himself.
London Fire Brigade said the man was using a charger bought from an online marketplace a day earlier.
The fire service warned the risk of an e-bike fire was "much greater" if users fail to buy the correct charger from a reputable seller.
Deputy commissioner Dom Ellis said: "We strongly recommend calling us immediately if there is a fire, but particularly if it involves your e-bike or e-scooter.
"Fires involving lithium batteries, which power these vehicles, can be ferocious, producing jets of flame.
"The blaze is also hot enough to melt through metal. This type of fire produces a highly flammable, explosive and toxic vapour cloud which should never be inhaled. The fire can also be extremely challenging to put out.
"This incident, and the severe injuries sustained by this e-bike owner, highlights why you should never tackle a lithium battery fire. Our advice is to get out and call 999."
It is the latest in a recent spate of e-bike and e-scooter battery fires in the capital, leading to calls for the government to tighten regulations of the vehicles.
On September 13, most of a shop in Bow, east London, was damaged after an e-bike battery caught fire.
The previous weekend, 80 firefighters responded to two separate fires in the UK capital believed to have been started by e-bike batteries.
The majority of a third-floor flat was damaged after an e-bike caught fire in Holborn, central London, on September 9, while the following morning flames spread from an e-bike charging in a garden to a block of flats in Penge, south-east London.
There have been at least 137 e-bike or e-scooter fires in London so far this year, LFB said.
Three people have died and another 50 injured in the blazes.
On Monday, the London Assembly Fire, Resilience and Emergency Planning Committee wrote to the government raising "serious concerns" over the regulation of the vehicles, and called for the Department for Business and Trade to outline what action it was taking to address safety concerns.
Lesley Rudd, chief executive of the charity Electrical Safety First, said: "Online marketplaces are a hotbed for substandard e-bike chargers, with our own snapshot investigation finding more than 60 that posed a serious risk of fire.
"Incompatible chargers can supply an e-bike battery with too much voltage causing a catastrophic fire and we want to see a ban on universal chargers that risk doing exactly this.
"Until online marketplaces are regulated like our high street stores, fires will continue."
Deliveroo was approached for a comment.