Sony a6500 Video Battery Life
The Sony a6500 uses the NP-FW50 battery. As widely reported, the battery run time for this camera is extremely low, but for video it's not that bad. I tested the battery using manual focus and video only shooting and was able to shoot for 1 hour and 10 minutes continuously in 4K (well with a restart every 29:50 due to recording time limit), so say 1 hour per battery to be safe.
When shooting stills and videos mixed with autofocus at a sporting event, I tend to get about an hour per battery also. Unfortunately Sony only makes a single battery charger that is pricey, so I am comtemplating this off-brand charger.
I hope that helps you in your planning!
Update Feb 5, 2019
I have been using this dual battery charger and off-brand batteries by Watson, which have performed just as good as the Sony batteries. The ability to charge two batteries at once is great considering how many batteries are required to make it through a shoot day with this camera!