On 18/08/2015 22:36, Malcolm Race wrote:


Not only Litium. 20 approx years ago my elderly mother was disturbed at
night by chirping noises which she thought came from her phone. She
reporrted a fault to BT and one of the first questios asked was 'Do you
have a smoke alarm?' She did, close to the phone. The problem was an
alkaline battery dropping in voltage as the temprtature dropped at night.


In my experience when the (alkaline) batteries start to fail in my smoke
alarms the chirping always starts at 2am/3am. Often ignored at night
the offending alarm cannot be identified in the morning after the sun
has come up and/or the central heating has kicked in.

The OP shouldn't overlook that there is also a battery in his digital
multimeter that may also be failing BUT readings tend to go high as a
DMM battery starts going flat.


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