I have a project that uses a DS1305 real time clock and it has been working for a while but it just started showing strange behavior, things like sometimes I couldn't read the time over SPI, the alarms weren't firing, etc. I have replaced the chip and crystal but still see the same issues, so I thought I'd try it without the backup battery and it seems fine without the battery but doesn't work with it in.

Has anyone got any ideas why the backup battery would have this effect?

Schematic attached

 

I have a project that uses a DS1305 real time clock and it has been working for a while but it just started showing strange behavior, things like sometimes I couldn't read the time over SPI, the alarms weren't firing, etc. I have replaced the chip and crystal but still see the same issues, so I thought I'd try it without the backup battery and it seems fine without the battery but doesn't work with it in.

Has anyone got any ideas why the backup battery would have this effect?

Schematic attached

Is your back-up battery so low that it is causing problems?

 

Sorry, meant to mention that I have checked the battery and it is still at the full 3V, even under load.