The other day Bunnings had Ozito 18V 4AH batts for $39, so I grabbed a few with a view to using them for 12V LED lighting - they're a much handier form factor than the 12AH gel cells I've been using. I tried an Ebay LM2596 buck converter module that I had laying about and did a bit of bench testing. Dropping the battery's 23V to 12V with a 0.6A load gave 74% efficiency, rising to 78% with a 1.1A load. Neither figure seems particular stellar, and means I'm losing around a quarter of the pack's 72WH capacity. Anyone know of a better efficiency converter for this voltage range?