Ay-ups Batterys

Depends - are you doing solo or a team? In team of four I used two half Epics and one full Epic for the higher powered light. I used three lights as the kit comes with three batteries so just ordered an extra light. They set up a charging station so people can recharge the batteries. I used someones spare charger for the third battery.

If you in a team of four then when finish your session recharge batteries immediately, so two batteries should be ok. If team of less than four or solo suggest spare batteries that can be left to recharge for longer. Don't forget to write your name on charger and maybe mark the batteries. If going solo, make sure your rear light can last the 12 hours.

HTH

Thinking of doing solo myself :/
If using three lights then you will need three spare batteries - if only two lights then two will do - means you need a quick change system and/or pit crew - a luxury I tape two batteries together, stick on some velcro to one and some to frame top tube then a strap round top tube and batteries - keeps them steady and easy to change. Helmet light I use extension chord and have battery in Camelbak.

HTH.

The Epics used to be good for six hours with the old emitters but with the new higher output ones it drops to about 4. Half epics are half the runtime.

If running bars and helmet together (mandatory if racing and / or you want to see) then you'll be using up 2 helmet batteries for every bar light.

So work out how long you expect to run under lights and stock up on batteries accordingly. Or borrow some.

I suspect you might come up short.

Just as an alternative, a local company Sonlight have a mountain bike light that is rated at over 900 lumens on high, and lasts on their standard battery for 3-4 hours. It also comes with a wide angle lens to spread sideways across the trail.
They are also releasing a battery for the Dusk till Dawn which is twice the duration. All this for a fraction of the cost of the Ayups ($140 each), which I sold so that I could buy the SONlights.