I found this on the FAQ:
"1 Hydrostick = 6 Duracell AA batteries, on average.
At 1W power output, 1 Hydrostick = 10 AA batteries (1 AA battery runs 1 hour at 1W)
100 charge cycles/canister at this stage, however can reach 500 cycles, even up to 1000 cycles.
6*100= 600 batteries. 6*500=3000 AA...