Just to report on the latest firmware 1.2.1 for 5D3, looks like it's no longer able to detect the 3rd party LP-E6 battery level anymore.
When I put my 3rd party LP-E6 (off-brand, bought from eBay) into the camera, there's a warning screen that says:
Communication with Canon LP-E6 battery is Irregular. Continue to use this battery?
If I choose Cancel, the camera will turn off instantly. If I choose OK, the camera will turn on & run as normal, but the battery level will stay at 100% all the time & I can no longer register nor delete the serial number.
This is kinda bummer for me as I just bought 18 DSTE-branded LP-E6s & I'm expecting it to arrive next week. If the DSTE-branded LP-E6s can't show the battery level, I'll be very disappointed.
Anyone else have this problem as well?