160 hours is for a 600 mAh zinc-air battery . The same size silver-oxide cell have a capacity of 200 mAh , an alkaline battery 150 mAh. The zinc-air battery have a flat voltage of 1.28V. I don't think the voltage was the reason , the capacity is slightly higher on silver-oxide cells that looks better in the datasheet.
Let's see pro's and con's for each option:
- zinc-air cells 3x4 series-parallel , 12 pcs , total capacity4x600 = 2400 mAh , total recording time 4x160 = 640h weight 2.3x12= 28g
pro: lightweight , high capacity
con:- needs air to work which can make waterproofing dificult, must be used after removing the seal.
- alkaline AA bateries capacity between 1800mAh and 2600 mAh , 2400 a good one ,3 in series recording time 4x160 = 640h , weight 23gx3=69g
pro: cheap
con: the weight is at the upper limit, linear discharge graph with low voltages at the end.
- 18650 li-ion rechargeable, battery45g up to 3000 mAh, let's say 2400 mAh ,3.6 to 4.2V voltage. Weight 1x45g , total recording time 4x160 = 640h.
pro: high energy density , appropriate voltage , can be reused.
con: needs a charger which can go over the budget , special cautions must be taken, an electrical short can make them explode so it needs a good mechanical protection.