Differential battery drain in my X5T?

[nattuggla]

I've just used up the first pair of batteries in it, and when checking just how drained they were it turned out to be a lot of difference. Not what I expected so I don't know which one had most use left.
Is there any explanation for this? I recall a thread from a while back about something similar, but that was in a torch which produces a bit of heat, which I don't think applies to an X5T, even if I often run it 20-30 min at a time.

 

[Charles Bradshaw]

The stainless steel head is a heatsink in the X5T. Some 123s can be weak, which would explain the differences.

The LEDs in the X5T are overdriven and this produces heat, which is bad for the LEDS. Hence the heatsinking. If the head end did not get warm, I would be very worried.

 

[nattuggla]

I probably never noticed it getting warm since most of the time I've used it for extended periods it's seldom been warmer than +10C.

 

[ChrisA]

If you have a DMM somewhere you could test both cells' flash amps . That's a nice and easy way to compare the left over capacity of 123s...

Chris

edited to add: About the reasons for differential discharge - I guess there are always small differences in capacity and internal resistance, even for 123 cells.

 

[Charles Bradshaw]

I think weak 123As are more common than we like to think. When I got my Legend LX, it turned out that one of them was weak. When you measure the voltage on them (after the light output dies) and see one is still good and the other is exhausted, then one was weak. This even happened to me with Energizer D Titaniums in my LW4000 (one weak, 2 good).

With the X5T, you should get 8-10 hours max light, followed by a similar period of less and reducing output.

 

[RussH]

I wouldn't expect a lot of difference, but it may be hard to tell with CR123s because of their somewhat unpredictable voltage characteristics. Dead ones often seem to have open circuit voltages of 2.8-3.2v, similar to fresh batteries.

My experience with any type of battery is that the one at the positive end discharges to a slightly greater degree than the one(s) at the negative end. It appears that electrons from one end of the battery string at least partly charge the batteries at the other end (negative end) of the string.

 

[JJHitt]

There was a thread on this effect with incandescent lights about a year or so ago. The answer, IIRC, was that the cell closest to the lamp was discharging faster (was more efficient) because it was heated by the lamp.

Might be the case here, as well....

 

[RussH]

I don't think there is much heating in my radio, which also has a slight differential in finish voltage/residual capacity. But you can get just a little bit more from a warm battery............