I wanted to breathe another lease of life into my oldie but goldie Metz CT4-60 series flash, which I used for many years for lighting during parties and other paid jobs. Nothing sophisticated about this unit, but a strong light source which with a Sto-Fen diffuser makes a capable setup. Lately the DryFit battery block, probably 20 years old, would run out soon after recharging, but the cheapest replacements I could find were $80 or more. Managed to pick on up for €12,50 in Germany at a specialist battery webshop (search for SONNENSCHEIN dryfit A506/4,2K).