Info adds up.
Battery discussions can get very long and depend on specific priorities in an application ... Alkaline AA's start out at 1.5 volts, Nicads or NiMH are 1.2 to 1.25 volts at fully charged. The Cortez and the Tejon you are looking at use 8 AA's, probably in series. Alkaline means 8x1.5 = 12 volts to the detector circuits. Rechargeable are 8x1.2=9.6 volts. Jabbo gets the voltage back with 10 rechargeables in his pack. You can get higher capacity (milli-ampere-hour) at same voltage in the same size package as the Energizers. They would take longer to discharge and will probably cost more initially. There are a lot of battery choices advertised when you start looking at the electric powered radio control car, boat and airplane hobbies. There are also a lot of battery performance and trade-off articles available from those hobby areas. The car, boat and plane experimenters also test battery cell resistance and how it affects circuit performance ... there are books available ... that is part of where discussions get very long.
I don't know the circuit specifics, but one way to show battery level might be to measure how far above the circuit regulator cut off you are and to show low battery replacement level when you hit cut off. If the battery indicator shows batteries in the good range but not high, performance may be OK until the battery indicator says to replace the battery. To be sure, you may want spend time with the specific detector with alkaline cells and then some time with the rechargeable cells to see when performance drops off. Then you have more actual use information about what trade off you make by going rechargeable.
The Minelab Excalibur II uses a custom rechargeable battery pack. I've read reports that you must use the very expensive custom pack or alkaline AA's. Using rechargeable AA cells in the holder for the alkaline cells do not add up to enough voltage to run it. That may be along the lines of where the convertible pack note is coming from.
Got to run for now.
tvr
