CTL2 BW Battery backup

Discussion in 'General Discussion' started by Trevor, Jul 1, 2026.

  1. Trevor

    Trevor

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    Hi all,
    I just had a call from a customer of mine he was asking about the time date backup as he has one that isn't keeping the time date correct ...
    Is it the large super cap on the PCB that is providing power for the backup CCT, and can this cap go bad in storage. What else is involved in backing up the time and date....
     
    Trevor, Jul 1, 2026
    #1
  2. Trevor

    NickD Moderator

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    Yes, the supercap is used to backup the RTC for short power interruptions. I've not heard of it going bad.

    It would be helpful to know what they/you mean by "isn't keeping the time date correct".. are they just talking about drift, or is it not working at all?

    The time in the CTL2 itself is only as accurate as the crystal (typically tens to hundreds of PPM). If all you have in your system is the CTL2 then there will be drift. Ideally you should have an edge device like a CTC, Wiser2, or Automation Controller which can connect out to an NTP server, which will then correct the time as needed.


    Nick
     
    NickD, Jul 10, 2026 at 3:08 AM
    #2
  3. Trevor

    ashleigh Moderator

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    Typical crystal accuracy / drift is around 15 mins / year. Doing better is possible but gets to be horrifically expensive. As Nick says, an edge device that can do NTP time sync is the best way to maintain accurate timekeeping.
     
    ashleigh, Jul 11, 2026 at 2:25 AM
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  4. Trevor

    Trevor

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    Thanks for the replies guys, he wasn't that clear on the time but I think he was saying it list it completely. He said he was going to try and replace the super cap himself so I guess if I sevit in the workshop it wasn't that.
     
    Trevor, Jul 11, 2026 at 3:37 AM
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