What battery do I need for a Seiko 0439 5007

[martin49]

I could use some help to source the right battery for a 70's Seiko LCD wristwatch. I removed the battery many years ago with the intention of getting a replacement but of course I have misplaced it. I measured the battery cavity and it is approximately 11.6mm X 2.54mm. I searched the internet and found silver oxide 1.55 volt batteries with the same diameter but their height was 3.1 mm for the #390 or 2.1 mm for the #381. I also noticed that the batteries came in high drain and low drain versions. Any help would be appreciated.

Thanks Martin

[rewolf]

Hi Martin, welcome

Low drain vs. high drain:
"High drain" is better for watches with functions that demand momentary high current (LED watches, alaram, backlight). It has less internal resistance, especially at low temperatures - i.e. the voltage will not "sag" so much when high current is demanded. On the dwonside, it has 5-10% less rated capacity than "low drain".
"Low drain" has slightly higher capacity but cannot deliver high currents due to higher internal resistance, especially at low temperatures. Their "shelf life" is a bit better.

Because a watch on the wrist rarely sees temperatures below 20°C when used, low/high drain does not make much difference.
Anyway, I'd use low drain only for analog or LCD wthout alarm/backlight. Just to be sure .

For your watch:

2.1mm high SR1120W = 391 (high drain)
2.1mm high SR1120SW = 381 (low drain)

3.05mm high SR1130W = 389 (high drain)
3.05mm high SR1130SW = 390 (low drain)

If the 3.05mm fit in, use them. They have double capacity.

For battery charts see this thread: http://dwf.nu/viewtopic.php?t=2583

[Old Tom]

Hi, correct battery for the 0439 (front or side button version) is a 389 (but you probably would never notice the difference if you fitted a 390 unless you used the backlight a lot).

[martin49]

I will try the 389. Thanks to all for responding. Martin