The standard user-replaceable lithium-ion pack for the Alpha T 20 and Alpha TT 25 dog collars — the same pack those collars ship with.
Because it comes off the collar without tools, a second pack is the practical way to run two long days without finding a charger: swap it at the truck and keep hunting. Garmin rates it at up to 68 hours on the dynamic update rate, 25 hours at a 2.5-second rate and 84 hours at a 2-minute rate.
