Hi all,
just a little clarification concerning battery capacity:
Amp-Hours do NOT add when batteries or rechargeables are connected in series!
Amp-Hours indicate how long you can draw a certain current from a battery. This quantity does not change when you connect two or more cells in series.
Another point to keep in mind is the power consumption of P48:
assuming two mics with 5mA each and an efficiency of the step-up converter for 48V of 80% we get
48Vx5mAx2/0.8= 0.6W or 600mW.
If we assume two NiMh cells at 2.5V (1.25V per cell), this amounts to an additional current draw of 0.24A only for P48!
Keep in mind that non-rechargeable AA cells (even Alkalines) have a rather high internal resistance that can lead to premature undervoltage shutdown of your recorder, especially with P48.
BTW a fully charged Li Ion cell has an open circuit voltage of 4.2V, and it takes some time to drop to 3.7V. Li Ion voltage is proportional to remaining capacity, so a simple voltage measurement ("battery bars") gives a good approximation of state of charge.
This is also true for alkalines, but not for NiCD or NiMH!
My advice: use good quality rechargeables with low internal resistance from reputable sources. Most of the well known brands have specifications online for their cells and state how they measure their cells. I would not bet on no-name products or e*ay bargains...
An example can be found here:
http://data.energizer.com/PDFs/nh15-2300.pdfhttp://data.energizer.com/PDFs/E91.pdfjust for grins: compare the internal resistance of alkaline vs. NiMh!
End of battery technology lecture
Greetings,
Rainer