Testing a mains voltage LED from China. This one is rated 220V and 20W. It really can be connected directly to AC mains with no LED driver. 30W and 50W versions are also available. In the listings it’s called “smart IC” or “integrated driver” or “driverless” COB LED.

Your big-top circus guide to why so many 100W LEDs are a pile of elephant poo.

Why 100 Watt eBay LEDs Are Not Your Friends
http://hackaday.com/2015/09/14/why-100-watt-ebay-leds-are-not-your-friends/

Case in point, [bigclivedotcom] has been testing of some 100 Watt LEDs from eBay. When these LEDs work correctly, they put out a face-melting beam of light that you wouldn’t dare looking into (picture the scene from Raiders of the Lost Ark). They also have some unusual specs for an LED, like running on 30 Volts – and that’s a lot compared to the forward voltage of most LEDs at around 2.5 volts@20 mA.

So what gives? Well many of these high-wattage LEDs use a string of several LEDs in series.

And as [bigclivedotcom] points out, this can be a real problem when a few of the LEDs begin to fail

Testing dodgy 100W LEDs from ebay sellers.
https://www.youtube.com/watch?v=NjKgPLeJ79Q

I bought some from two different ebay sellers based in China and deliberately tried two different price ranges to see how price affected quality.