@Gerald Marafioti posted:... i thought that it had a load built into the meter
It's a 370 Ohm Resistor load; the HF "manual" calls it a 370 mW load. Whatever.
The math is Ohm's Law: Current = Voltage / Resistance.
1.5V battery. Current = 1.5 V / 370 Ohms = 0.004 Amps = 4 mA
9V battery. Current = 9V / 370 Ohms = 0.024 Amps = 24 mA (close enough to 25 mA)
When you read "only" 3.5 mA with your rechargeable it's because the battery voltage was about 1.3V under the 370 Ohm load. Current = 1.3V / 370 Ohms = 0.0035 Amps = 3.5 mA
As to whether 1.3V is "low" is a function of how your electronics gadget was designed. There is a so-called voltage-discharge-curve which characterizes how the voltage in a battery drops over time. Problem is it depends on many things from the battery chemistry, the temperature, the load current, etc.. At some point in the design of your electronic gadget, an engineer had to choose a voltage threshold below which the "low battery" icon turns on. And because of the variations in the discharge curve between battery types, a "low battery" can mean vastly different actual remaining operating time.
