bad battery?????

[Shiniquiet]

On my gf Executive Pulsar today (which I don't wear all that often) I noticed the display to be weak. It's been a while since the batteries were changed so off I go and pick up a couple of 386 batteries. Since I don't do this often, I neglected to notice if they both were placed in the module (402, I think) the same way or if one was up and one down. I tried different combinations until the display lit up nice and bright. The locking ring put up a fight and by the time I got in on and checked the display it wasn't nearly as bright as when I first put the batteries in. Took the thing apart to check the batteries and found one battery to be hot (not just warm, but hot) to the touch. Switched the batteries and the display lights up bright. Put it back together and the display can hardly be seen. Take the watch apart and the same battery is hot. So, my questions are: Could I have purchased a bad battery? Might I have done any damage to the module? Or, am I just doing something incorrectly? Any insight would be most appreciated.

[Shiniquiet]

I think I resolved the issue. After the initial panic subsided, I did some surfing on the net and found a battery chart on Ed C's old site. It turns out that the watched and it's module needed 357 batteries. Picked up a couple of them and installed. Tada, everything seems to work. The irony in all this is that the 386 batteries were what were initially in the watch and it appeared to work fine. I just hope that my fooling around this afternoon didn't screw anything up with the electronics.

[charger105]

Both 386 and 357 cells are 1.5V, and will theoretically run the watch perfectly well. The 357s will last longer because they have a larger capacity.

The fact that one of the cells got hot, and the display dimmed almost certainly indicates that the cell had its terminals shorted. In other words, the positive and negative terminals were bridged to each other by metal and delivered a large amount of current (through that piece of metal) in a very short time. It would have very quickly depleted the cell.

I'd say the 386 moved around (because it's much thinner) and the butterfly clip probably bridged both terminals.

BTW, you can easily tell how a battery is to be inserted. If the bottom of the battery well is bevelled, then it's negative down. If it's a 90 degree transition, then it's positive down. On the P4, it's also engraved on the plastic carrier
Rgds.

[bucko170]

As far as I know the only difference for practicable purposes between the 357 and 386 batteries is the size, both batteries should function equally as well in the watch and should not be getting hot.

I would be concerned about the potential damage that could be caused by putting the batteries in the wrong way and therefore reversing the polarity of the batteries. Clues to look for to get the batteries in the right way are any obvious markings but failing that the battery well that takes the battery negative side down is sometimes tapered at the bottom - as shown in the photo (on the left).

Pulsar Module Back 8 Forum.jpg

[Shiniquiet]

I never noticed that one of the battery slots was beveled. I'll be watching for that the next time as well as taking special attention to which battery goes which way.

Many thanks for the responses.