DrMichael I haven't yet received my unit so the following is just me general understanding of electronics. First, it depends on the capacity of the 18650s you put in. If they are, say, 3000mAH then the total ... I haven't yet received my unit so the following is just me general understanding of electronics. First, it depends on the capacity of the 18650s you put in. If they are, say, 3000mAH then the total nominal capacity is 48,000mAH over 16 cells at a nominal voltage of, say, 3,7V. Second, taking the capacity as 48,000mAH, and assuming, say 90% efficiency for boosting from 3.7V to 5V, you can expect around 32,000mAH effective capacity at 5V. (48000*.9 x 3.7 ÷ 5). Hope this helps Voir Plus