Timers that keep good time?

New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
I use timers to kick several things on and off during bulk charging, like the water heater, laptop charger, etc.

Unfortunately, all that I have tried keep terrible time, and I have to adjust them once a week or so.

Can anyone recommend a 15 amp capable timer that actually keeps good time?


  • RCinFLARCinFLA Solar Expert Posts: 1,351 ✭✭✭
    edited December 2020 #2
    If you get one that takes its timebase from AC mains, no battery backup, (assume you have grid) should be pretty accurate because power grid compensates any variance over time.  Only issue is if you lose power you get blinky.

    Most clocks with 32.768 KHz clock crystals run slow because their designers don't take the couple of pF of PCB runners stray capacitance loading into account.  The crystals temp coefficient is an inverted parabola so the farther away from room temp the slower they run.

    I have tweeked several clocks by changing their 10-12 pF xtal load capacitors.  But you need an accurate timebase to do so.

    You miight find one that uses WWVB.  Typically named 'atomic' clock.
  • PhotowhitPhotowhit Solar Expert Posts: 5,580 ✭✭✭✭✭
    My family used a graybox timer at home for years and I installed one on a pool where I worked security. Once set, I don't think any of them had to be reset. Both were working off of grid electric. 

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • mike95490mike95490 Solar Expert Posts: 9,276 ✭✭✭✭✭
    My inverter runs a bit fast, so all my clocks and timers run a tad fast too.  nearly any AC powered clock gets it's time from the 60hz power line.  Grid power, over a week or so, should be very accurate - but with changing loads day to day may vary a hair.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 31,690 admin
    DC Timers/Clocks (some battery based) are usually the answer vs Inverter AC power (and the less than ideal 60 Hz--And MSW inverters sometimes "confuse" timing circuits):


    I have found that there are Digital AC timers that (appear) to use a crystal time base--Usually see something like this:

     The battery backup assures you stay on schedule even after a power outage. Our product has an internal battery that will last 3 months when not plugged into an electrical source. If the battery needs to be recharged, plug it into an electrical source and allow it to charge for 30-45 minutes. 
    I have also had Digital Timers that have a couple watch batteries in a side compartment for the "loss of power" timer operation.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    Wow, lots of info I had no idea about. I'm off grid.  Ill be checking these out!  Thanks as always.
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