Four fire engines and around 25 firefighters were called to a fire on Ludlow Close in Harrow.
Part of the ground floor of a terraced house, along with its fascia board was damaged by fire. Decking and a fence were also alight. The fascia board of a neighbouring property was also partially damaged.
Firefighters removed and cooled two gas cylinders, which were involved, to an ambient temperature, as some cylinders can explode when exposed to heat.
The Brigade received the first of around 30 calls about the fire at 1537 and Control Officers mobilised crews from Harrow, Wembley, Ruislip and Stanmore fire stations to the scene. The fire was extinguished by 1638.
The fire is being treated as accidental and is believed to have been caused b the failure of a lithium-ion battery in a speaker.
Lithium batteries store a significant amount of energy in a very small space and are much more powerful compared to other types of batteries. If that energy is released in an uncontrolled way, then a fire or explosion may result. If there is overheating, crushing, penetrating or overcharging, then a fault can occur within damaged battery cells which may cause the battery to catch fire.
A London Fire Brigade spokesperson said: “Lithium batteries are susceptible to failure if incorrect chargers are used, so it’s important to always use the correct charger for the product and buy an official one from a reputable seller.
"You should unplug your charger when you have finished using it and we would advise not to leave it unattended or charging while people are asleep.
“Batteries can present a fire risk if they’re over-charged, short circuited, submerged in water or damaged, so it’s really important to protect them against being damaged too.
“Try to ensure they are not getting knocked around while in use or while being carried as this can increase the chance of damage to cells."