In simple charging, it heats up a lot but luckily I have rooted my phone and I can charge for 10 minutes and stop for 5 minutes for the charger to cool down... useful if you leave it charging overnight but not during the day if you need fast charging... for any old phone that doesn't require much power like headphones/watches, etc. it's fine but for modern beasts that charge at 5 amps, it's better to get a fast charger.