Six fire engines and around 40 firefighters tackled a fire at a recycling plant on Smugglers Way in Wandsworth.
Around 100 tonnes of mixed household recycling inside a waste disposal site was alight. There were no reports of any injuries.
The fire is being treated as accidental and the most likely cause is the failure of a lithium battery.
A London Fire Brigade spokesperson said: "Lithium batteries should not be placed in the same bins as your regular rubbish or recycling. If they overheat, they may cause it to catch fire. Instead, check your local authority's website for the safest way to dispose of lithium batteries in your area.
"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.
"Batteries can present a fire risk if they're overcharged, short circuited, submerged in water or damaged, so it's really important to protect them against being crushed and dispose of them safely."
The Brigade was called at 0046 and the fire was under control by 0332. Crews from Wandsworth, Battersea, Fulham, Chelsea and Tooting fire stations attended the scene.