Well aware that this is a very vague question. I am thinking about getting a new body. I currently shoot with a 7D Mark II, a 1DX, a 1DX Mark II and Mark III. I shoot motorsports. Lot of very low light stuff. Love my 1DX Mark III. Love the fact that I can get over 3k images a battery. Not really concerned with the fact that Canon has pulled the plug on mirrored bodies. But I am intrigued by the R3. Spent some time talking with a friend that has one, he told me that the R3 is an incredible piece of equipment...sadly battery life is far from incredible. I understand that the R3 is all electronic which does not help in regards to battery life. I have read all sorts of reviews on line, many of which say that 600 or so shots is about it on an R3 battery. Just looking for honest answers. Thanks
As the Canon CIPA numbers provided by John state, the R3 should be able to produce about 620 shots with a new, fully charged LP-E19 battery. I don't have a R3, but my personal experience with the R5 and the R is that the Canon CIPA numbers are accurate. Canon rates the R5 at 220 to 490 shots on a 15.3 W/hr LP-E6NH and I typically get up to 500 shots using the BG-R10 Battery Grip (2X LP-E6NH or 30.6 W/hr) with all viewing through the OLED Viewfinder, IBIS usually on, and very little image review using the LCD screen .
Since the R3 uses a LP-E19 (29.7 W/hr) 500-600 shots should be achievable assuming you don't use shutter button pre-focus or back focus or long viewing on the LCD screen excessively.
I also shoot some motorsports with the R5, and one caveat which may or may not also apply to the R3 is that the highest frame rate shooting (at least on the R5 at 12 fps) is not available when the battery charge drops below 60%.
Have no idea if this also applies to the R3, but on the R5 w/Battery Grip I always carry extra batteries and switch them out when either one drops below 60% when I'm shooting at Road America and Mid-Ohio.