Edit 07.07.18 - voltage drift of single cells in a battery pack?
It is often mentioned using a single Li-Ion or LiPo cell is better technique, because of 2 or more AA cells one will die sooner than the others.
I bought Ansmann industrial cells for my loggers, which had no difference in cell voltage out of the box.
It's exactly like that after 2 months: Two cells are 1.439V, one is 1.440V. So everything's in perfect condition!
After two months of the logger being "in the wild" I can estimate how much the circuit drains from the batteries.
It's been a steady 0.1V/month for two months now. At the moment the 3xAA batteries dial in at 4.33V (didn't measure each single value). The logger stops operating at 3.6V.
So if everything stays the same, I should get another 6 to 7 months of logging. Of course some other factors come into play here:
- battery voltage is higher in hot weather conditions
- ability to deliver higher currents (SD open/-writes...) goes down with lowering battery voltage
But I expect only about 4 to 5 more months before I change the batteries for fall/winter logging because the above reasons.
I'll get another V1.2 logger out by then, so I can compare them after the winter period.