Haven't tracked a deer in a long time at night...most every deer we kill is in the morning and I prefer it that way. The ones we have shot in the evening have fallen within sight so that helps too.
If I was to have to track I would use my little Bushnell clip on light on my cap brim...
I have kids so the only light I tend to have that has batteries in it that work tends to be my dewalt battery powered work light. Anything else in my house is a "toy" and will be used until dead and then returned to the drawer! I have a battery on the charger at all times and another on the light itself. It's heavy and the like, but it's what I use. I'm sure there are others that are much better. I have seen the red/green blood tracking lights (my buddy bought one) and I was not impressed. I'll take a good bright light and patience any day. I like a light that makes me focus. A wide light causes me to want to "scan" and that can be bad. I don't like one that is too small that makes finding anything nearly impossible either. Waterproof is real nice to have as well. I don't carry my "tracking light" with me when I hunt. I hunt where I live so I will go home and get my "tracking pack" to track a deer if needed. It also forces me to give the deer some time as well.
I carry two lights......I use my headlamp for in/out walks and thus 90% of the time. When I shoot a deer at night, I use both my headlamp and a small pelican led flashlight.....id have to check the model, but its bright!
It uses a single 18650 (specialty) battery. It has multiple different lumen setting and lasts for many hours on low settings. I think I get over an hour on high setting, but it gets too hot to run that way for more than about 10 minutes. Typically I use 75-100 lumens when we are moving and save the really bright light for really searching for sign. I have one of the wizard pro models. I spelled the name wrong before. It is armytek.com.