Our best light is a Light and Motion Arc HID light. About 700 lumens. Nice and bright. Old technology though. I bought two others of these off Ebay. One doesn’t work at all (ballast probably bad). The other works for a while and then dies. Again, probably bad ballast. Not sure if it’s worth sourcing a ballast or buying a new LED, like a L&M Stella.
Our second best light is a NiteRider Enduro HID. Again, older technology. It’s pretty bright, probably 5-600 lumens. Only catch is, it doesn’t like cold weather. Doesn’t fire up when it’s cold. Works well in warm weather. CyclingGirl and I joke it needs a little romance before using it (e.g. sticking it down your pants to warm it up before use ).The ballast is probably going. Someone is selling a ballast that may work for both lights on Ebay for about $70.
I’ve got an old BLT halogen light as a backup, but it’s pretty dim. One or more of the NiMh batteries is probably gone. Not sure if it’s worth trying to replace the batteries.