This roadwork warning lamp has been with me for years, and after not having done anything fun with it since then, I decided to try to convert it into a portable power station with some Li-Ion batteries, a solar charge controller, a proper lamp, and whatever else I can fit in there.
These lamps normally run on big chunky 6V batteries, but I'll try to replace them with 18650 Li-Ion batteries, in a 3S configuration (11.1 V nominal).
I don't have the means to make my own welded battery pack quite yet, so I'll use these 18650 battery holders for now. Two of them go back to back and fit very well into the spot where the batteries were before, so I'll have a 3S2P battery configuration for now. That would give me somewhere around 400-500Wh of battery capacity, depending on what kind of 18650 I decide to get. Not great, but good enough for a start, and I can always build a bigger battery pack later.