Battery internal resistance and metal detectors

[Trailboss]

My question concerns the effects of a batteries IR on the ckt.

My question comes from the fact that when using a Lithium battery in the metal detector performance is enhanced, ie: louder audio, deeper target depth.

This does not seem to be subjective, but something that has been noticed by myself among other very seasoned Detectorists.

This enhanced performance was experienced when switching from NiMH or Alkalines.

The Lithium is the Energizer ultimate lithium AA cell providing 6 volts.

I looked at the D/S and saw the alkaline and the NiMH have roughly the same IR, about 30 to 40 milliOhms.

The lithium was 3 to 6 times that value, 120-240 milliOhms

The metal detector is a Garrett AT Pro VLF unit.

I know Lithiums have a slightly higher voltage, but I would think that the Garrett would have a regulator ckt in the supply.

What could be the Mojo Magic happening here,

Any body want to throw there two cents in???

TIA

[johansen]

I suspect they do not have a regulator.

[SeanB]

Very likely the higher voltage, as most metal detectors do not use voltage regulators, so the peak pulse power will be higher from the increased voltage, and the audio will be slightly higher from the same reason. If using NimH cells you probably will want an extra cell in the pack, using a 5 cell pack would give the same performance as the battery voltage from a 5 cell pack would be 6V typically, as opposed to 4V8 from a 4 cell pack.