Voltage drop / batteries

[Macthediver]

Hi guys
I was wondering if anyone here could tell me what I could use as a voltage number to replace the batteries on my minelab Excalibur. I have two battery packs one rechargable one that takes 8 - AA batteries. I usually run either one till the unit starts acting up then replace or recharge the batteries. It's easy enough to just charge the rechargable pac when I get home after hunting. But I'd like to save myself some grief and at least have the AA pac as a full power back up each time I go out. I know it's not a big deal to just replace the AAs in the field. But if I can save some field time by putting the meter on the pack at home and changing the AAs there it would be nice. I have no way of testing the batteries under load. So I'm looking for a ball park voltage number on just the pack where I could expect the machine to start failing.
Any help would be appreciated.

Mac

[Merc]

A rechargeable cell will usually give you about 1.25 volts per cell. 8 x 1.25 should yield about 10.0V. 8 AA alkalines will give you 12V. I'm reasonably certain that your detector will operate just fine on anything between 8 and 12 volts due to the internal voltage regulators. But back to your question, I would say get rid of them when you measure around 10V unloaded.

Merc

[Unregistered]

Thanks Merc
When I ask the folks at Kelly Co about it they said why are you concerned if the Alkaline AAs are a back up to your recharagable pack? Then we did some circle talk that didn't answer the question.

If I run the rechargable pack first which I normal do. Most everyone knows when rechargables run out they go all at once. So then I put on my AA pack on as the back up. I've been doing this with the batteries in the AA pack since last August. I didn't run them during the winter months as I didn't use the detector. After I came home from several hours detecting the other day I decided to check both packs just out of curiousity. I did charge the rechargable pack first so I would have a comparison for the AA pack. The rechargable was at 12.V something that I don't recall now of the top my head. The AA pack however was at 11.54V thus my question on when will the voltage effect the operation of the detector.
If I know to just replace the AA batteries at say 10V as you suggest then I won't get caught in the field with AAs just making the machine stay alive instead of truely working. I don't want to waste batteries just blindly replacing the AAs or waiting for them to catch me by dieing either.

Thanks again
Mac