The back cover of the Iwork 20 Pro is NOT a snap on type cover. It is glued on but can be removed to access the battery by using a very thin tool to start a separation spot and then using a thin kitchen knife, gently work your way around the frame until the cover is completely free from the back of the tablet. Be careful not to bend the cover. No need to remove the micro SD card or the fiip-out Back rest. Do not separate the front glass part of the tablet. The diagram A above in frank77’s post is the thin metal back cover to remove. I removed the battery using small Phillips head screwdriver to remove the screws securing the battery and then unplugged the battery. Once the battery was removed, I taped the cover back on temporarily using Duct Tape so I could use the tablet with DC Power supply brick while waiting many weeks for a new battery to arrive from AliExpress.
