I used a separate digital volt meter across the actual batteries in the above test.
I used a separate digital volt meter across the actual batteries in the above test.
I'm think I'm beginning to see some interesting things.
When connect to a PC and running Scan125 the voltage on displayed on the scanner by depressing the volume knob and the voltage shown in the program are the same. Also the voltage increases over time as the batteries charge so on my UBC125XLT it IS the battery voltage at the terminal. NOTE however if I remove the USB cable and press the volume know for voltage it is lower and on the test I just did it was below 2V and the scanner powered off.
With no batteries in then the scanner displays no voltage (blank) but Scan125 reads 0.06V. A DVM reads 0.058V
Now the odd thing.
If I put the battery switch to ALK and power the cycle the scanner then I get the same results. At the moment I have to conclude that there is always a nominal voltage at the battery terminals when connected to a USB powered lead AND batteries are present. However in my case I did with old NiCd and not well charged so batts and NOT NiMh.
I don't currently have (or can't find) any NiMh batteries. The scanner charging circuit could be differentiating between battery types.