Hi Reg,
I took a spare TDi battery pack apart, as these are made of 18650 cells. It had 4800mAh on the pack of 8 cells, so that must be 2400mAh the for each cell, as they are paired. I have paralleled two together to give 4800mAh which theoretically gives just over 13 hours on the Vallon VMH3CS detector. I am assuming the cells that Whites use are of good quality. They have one circuit board built into the pack but that is for 14.4V. I discarded that.
The Vallon detector derives all it's voltages from an onboard converter; even the supply for the bipolar TX. Performance on coins and rings is outstanding, as I will report later. As the batteries run down the current draw from the converter goes up and none of the voltage rails change. The detector automatically shuts down at 3.0V and gives a constant tone.
My next problem is charging the battery. So far I have used my bench supply set to 4.1V which I gather is a safe way of charging, but not necessarily to a full capacity. I'd like a fast charger, but it must be safe.
Eric.