Honeywell RPLS40B Programmable Timer Switch: Fix broken backup power

[RonJ.]

Honeywell RPLS740B Programmable Timer Switch: Fix broken backup power

I obtained a used RPLS740B timer switch that no longer retains the time setting after a power outage because the battery backup feature doesn't work.

I removed the rear backing of the timer and discovered that the backup power comes from a supercapacitor (Eaton Powerstor KR-5R5H474-R, 0.47F, 5.5V) soldered to the circuit board. The supercapacitor costs about $5.50 from Mouser Electronics.

I ordered a replacement supercapacitor, and also bought this soldering kit (http://www.amazon.com/dp/B01712N5C4/?tag=atomicindus08-20), which costs about $23 from Amazon. Using the soldering kit, I removed (desolder) the bad capacitor and installed (solder) the new one on the circuit board.

After reassembling and installing the switch, I let the capacitor charge for 24 hours. When I shut off the power for 2 hours, the switch saved the time setting upon restoring the power. The switch is now fixed because prior to replacing the supercapacitor, the switch lost its time setting after shutting off power for less than 30 seconds.

I hope this helps others whose timer switch has a broken power backup.

 

[The Cobbler]

Lots of things can be fixed if someone has the ingenuity and gumption. Unfortunately we're in a throw away society & very few people take the initiative ( or have the skills) to repair.

Good on you!

 

[RonJ.]

Lots of things can be fixed if someone has the ingenuity and gumption. Unfortunately we're in a throw away society & very few people take the initiative ( or have the skills) to repair.

Good on you!

 

[RobY]

I know this thread is old, but I I had to correct some erroneous information. The capacitor is a .22f, not a .47f. The .47f might work, but it's not the right capacitor for the job. The Eaton P/N is KR-5R5H224-R.

 

[PowerJP]

On mine it's a 0.47F

 

[SkidMark]

Thanks for the information, I was able to fix two of mine that were not keeping time after power was off for less than a minute. Both of mine were purchased late 2014 and each had the 0.47F, 5.5V supercapacitor.
I would suggest while you are changing the supercapacitor to check the solder connections for the relay. One of the units had a cold solder joint.

 

[mm08822]

The 0.47uF will store 2X more energy than the 0.22uF. It justs takes longer to charge.