Every time I remove the battery of a Canon 50D, even if it's just for a second, the camera forgets the current date and when turning it back on after the battery change I have to set the date again.

The little cell battery that should prevent that is inserted correctly and measures 3.2V which should be fine.

What could be the cause of this / What can I do to fix it?


1 Answer 1


I'd change the CR2016 anyway* - they're only about a buck even at full retail price - & see if it improves. Also give the contacts a quick spray with contact cleaner or 90% isopropyl & allow to dry fully.

If it doesn't improve, then you're probably in for more costly repairs.

*It's almost impossible at consumer-level to measure a voltage under load. I know there isn't much in the way of load on a tiny backup battery like this, but you can still only measure it unloaded with a multi-meter.

  • 4
    \$\begingroup\$ A 50D is old enough a button cell is end-of-life anyway. Replace it and be done. \$\endgroup\$ Jun 8, 2020 at 23:25
  • \$\begingroup\$ +1 for your conclusion, but my least cheap multimeter (~US$30 new) has a voltmeter setting for loaded testing. It draws 70mA if "1.5V" is selected, or 10mA if "9V" is selected. The latter is a little high for backup batteries, but suitable for other uses of coin cells, so it would be a good test for a suspect 2016. Or just use a through-hole resistor and any multimeter, but I appreciate not everyone has a box of those lying around. \$\endgroup\$
    – Chris H
    Jun 9, 2020 at 9:00
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    \$\begingroup\$ @ChrisH - it's still a bit of guesswork… In my last job I [& all the other engineers] had to test hundreds of power supplies out in the field. We devised & built a simple box you could plug them into which would simulate true load for the intended devices [LCD screens] & provide a simple green/orange/red LED feedback as to whether they were good or needed replacing. For a coin battery, it's simpler to just replace it ;) \$\endgroup\$
    – Tetsujin
    Jun 9, 2020 at 14:28
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    \$\begingroup\$ @ChrisH Just change the battery. At worst you're out a buck or two and know at least one thing it is not. Also check to make sure everything is tight enough for the battery to be making good contact for both the + and - sides when inserted. \$\endgroup\$
    – Michael C
    Jun 9, 2020 at 18:42
  • \$\begingroup\$ If you don’t have any isopropyl alcohol, vodka is a good substitute. Had an EE uncle who worked for NASA in the Apollo era. He never went anywhere without a flask of vodka that came in handy, more ways than one! \$\endgroup\$ Apr 28, 2022 at 12:00

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