I've been vacillating between using water bottles vs a Camelbak for hydration. The Camelbak won't freeze, but I'll have the "clammy sweat halo" around it.
Very familiar with batteries going flat in the cold. My headlight runs off my dynohub, and I have a dyno/USB converter to charge my phone (which I use as my bike computer). Taillights will be a problem.Maybe I'll keep my spare in my back pocket. The only other thing is my bone-conduction headset, for which I bought a new power bank especially so I could recharge it during this event. That might not work. So it goes. I will have an ice chest at my pit station--maybe I can use that to keep things from getting too cold.
I'll be bringing my cool-weather gloves and my cold-weather gloves (which are too warm above freezing). I actually don't have any full-length cycling tights--I have leg warmers, and cold-weather shorts, knicks, and long wool socks, and running tights. I'll figure something out. I've got a neck buff to keep half my face warm, but that may fog my glasses. We'll see (or not, depending). I've got a fancy high-tech base layer that fits very snug, and various wool undershirts, so I can probably manage two base layers. I've got a Perfetto jacket/jersey thing that's pretty good, and a rain jacket I could wear over that. I think my core will be OK.
The loop has a total of 312 feet of climbing over 6.2 miles, so 50 feet/mile. Not a big concern. There shouldn't be any ferocious descents to chill me.
I've had long rides, and I've had cold rides, but this will be the longest, coldest ride I've done.