Nope, the light head works great with other batteries
I liked it. It's "just enough" light to make commuting possible on a dark forest MUP. Not light-up-the-night like their HIDs, but it's also 1/4 the cost. The Solo is totally weatherproof, from what I could tell. The connections seal well, and I had no problems riding in driving rain. The mount system is nice; quick to mount/dismount, and the light head pops off with no tools (if you like to flip your bike upside down to work on it like I do, this is great).
It's the least amount of light I'd want on my commute, which takes me through some forested areas with no light. I would prefer a little more light, but as I said, the Solo is "just enough."