Energizer Ultimate Lithium is a primary (non-rechargeable) cell known for excellent shelf life and tolerance to high and very low temperatures, good discharge characteristics, and little to no leak risk. The downside is theyāre a little bit pricey, but have been getting better lately. Itās an excellent option if youāre ok with the price.
Alkalines will work well in this light from a runtime perspective, especially the reduced output that occurs after the first 8-10 hours of operation. However, there is the ever-present leak risk that has to be considered for alkalines. Iāve had good luck cleaning up alkaline leakage with vinegar, so I might still use alkalines in mine. I havenāt decided.
Rechargeable nickel metal hydride (NiMH) batteries have very good discharge characteristics, a low potential total cost of ownership due to being rechargeable, and little to no leak risk. However, their lifespan is shortened if over-discharged, and this light is capable of over-discharging them. Recharging when the light gets noticeably dim will probably be reasonable protection against that.