Wireless Davis VP2, 6162 weather station - ISS super/ultra capacitor


29 Jun 2015
UK:52°12'N,0°07'E; DE:47°40'N,9°10'E; PT:40°N,8°W
If a newly replaced 3V lithium 123 battery runs flat only after 3 or 4 months, causing the outside measurements (temp, hum, rain, etc.) to be lost then very likely the super/ultra capacitor (10F, 2.7V) in the PCB inside the integrated sensor suite (ISS) is faulty and needs to be replaced.

After having to replace too many times this battery in a short period I tried to find what might be the problem. Amazingly (or maybe not) the Davis website didn't mention this problem at all.

Fortunately other people have had a similar problem and the solution was always the same: replace the super capacitor. Apparently this problem affects most of the Davis wireless stations built until 2008 or 2009.

To access the PCB just remove the small screws securing the white lid.
If the capacitor had burst then its dielectric material will leak through the positive terminal lead/pin. This can be seen in the next two photos:



The capacitor can be replaced without actually having to remove also the PCB. In my case I just cut the leads of the old capacitor and then soldered onto the cut leads the new capacitor. This can be seen in the next two photos.



As the weather station was is in a remote place I had to use a battery powered soldering iron. It is important to first remove the 123 battery before doing any work on the PCB.

The new super capacitor has a capacitance of 25F, much higher than the previous one, so hopefully the 123 lithium battery should last even longer. I bought the super capacitor in here [1], it cost about 4 eur.

Hopefully this might help someone having a similar weather station that is tired of losing weather data and buying too many 123 lithium batteries. I replaced the capacitor one year ago and have not had since then any "low battery" message on the console.

[1] <http://www.mouser.de/Maxwell-Techno...-Ultracapacitors/_/N-5x76s?P=1z0ixuiZ1z0x2ud>
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