I have been doing an experiment with a battery pack I have been building as a hobby for remote use of a simple low power DC device.
For this purpose, I put together a battery pack with 12 AA 1.2 V NiMH batteries in series (DC).
The load on the device itself is just a 5 W - 20 ohm resistor to keep things simple. I calculated the estimated resistance of 7 ohm for the battery holder (boy, are those cheap units) and 3 ohm for the wires, connectivity and unknown. Meaning a total resistance of 30 ohms in the circuit (not counting the battery resistance).
I am using 2000 mAh batteries or greater. After a full charge, I put the batteries in the unit and run it.
For my latest test, the voltage at the combined battery starts at 15.27 V (with load) and over one hour drops to 14.39 V. After the second hour it drops to 12.64 V. It typically does not make it to a third hour based on my test so far.
Incidentally, the power supply for the unit is an AC-to-DC 12 V 1000 mAh unit. When I check the voltage on this power plug it nears 14-15 V for the power supply.
Is there a way to efficiently limit the power with a switching device to 12 V (or something else)? I would like to extend the life of the battery power if possible.
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