Topic: I finally had a bad supercapacitor

[miraculon]

This morning, I saw that my meteohub plot for the Novalynx rain gauge wasn't displaying. After checking multiple receivers/meteo-bridges I could see that the data hadn't been received since about 10 PM (EDT) last evening. Apparently it must have been running on battery and it finally fell below the point where it could operate.

The solar panel voltage was less than a volt under load, comparing it with another SIM transmitter which was >2V even out of direct sunlight. Open circuit it was well over 2V. I took the transmitter down and removed the cover. There was severe corrosion on the 10F 2v7 cap.

I had a 50F 2v7 cap still in the original package from years ago. This was much larger diameter than the original, but it fit under the cover. I put a fresh battery in, but I am wondering if it could go all night with the bigger cap...

Back up and running again.

I'll include a photo of the bad cap.

Greg H.
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[DaleReid]

Greg, I think you certainly found the culprit with that picture! 

With the much larger supercap, will your panel be able to bring it up to charge?  That would be the only question I can see.  AAA vs. D cell, both are same voltage, but one has a lot more reserve.

[miraculon]

Greg, I think you certainly found the culprit with that picture! 

With the much larger supercap, will your panel be able to bring it up to charge?  That would be the only question I can see.  AAA vs. D cell, both are same voltage, but one has a lot more reserve.

It came up and was working almost right away with no battery connected. I only had a desk lamp shining on the solar panel and turned on DIP #4, which started blinking. It wasn't like it took a while to get going.

I have not measured the supercap voltage itself. Indeed, it has been coated with conformal now and I can't directly probe it anymore.

Just happy to get it working again.

I am debating to pop the inner cover on other transmitters and inspect the supercap leads for crud.

Greg H.

[DaleReid]

Sounds as if you have had more success than I have today, with mine being a few small ones.

Did the replacement come with some of that conformal goop to pour over the area where you soldered, or did you have some you use for other projects?

I'm asking because I will need some in a bit and looking for a good brand and type.

It would be interesting to know what the voltage is and how it curves up as charging goes on.

What other transmitters are you feeding the station with?
Dale

[miraculon]

Sounds as if you have had more success than I have today, with mine being a few small ones.

Did the replacement come with some of that conformal goop to pour over the area where you soldered, or did you have some you use for other projects?

I'm asking because I will need some in a bit and looking for a good brand and type.

It would be interesting to know what the voltage is and how it curves up as charging goes on.

What other transmitters are you feeding the station with?
Dale

Did the replacement come with some of that conformal goop to pour over the area where you soldered, or did you have some you use for other projects?
I got the conformal from Amazon, but they show it as "Not Available" along with some other suggestions.

It came up on Digi-Key: https://www.digikey.com/product-detail/en/mg-chemicals/419D-55ML/473-1388-ND/9657990

and Mouser shows it as obsolete. Digi-Key only has 3 bottles left. I didn't want spray going all over the place and I liked the little brush. I originally bought it when I repaired my water heater/cooler when the compresser relay stuck on and I had to replace it. Looks like Amazon shows some alternatives for the conformal I bought.

Capacitor Charging TimeToo many dead brain cells to do the Calculus any more, but I found a handy calculator on line for charge time.
http://www.learningaboutelectronics.com/Articles/Capacitor-charge-calculator.php

In my head, I was reasoning that 1 Tau would of course be Resistance x Capacitance. Assuming that we had 1V and charged the cap with 1A, this would be 1 seconds assuming a 1F capacitor. Some online references indicate that 5xTau (where is the Greek symbol when I need it) would of course be 5 seconds for the 1F and 1V case.

Bumping this up to 50F and plugging 2V into the online calculator, give a full charge at about 5 minutes. 2V was from what I saw coming out of the panel no-load. Of course the variation of the solar panel voltage with sun angles, cloud cover, etc. YMMV. But, it gives an idea that 50F should be no problem to charge up.

If somebody wants to grind through a more rigorous analysis, have at it.. For me a "quick and dirty" idea is good enough.

What other transmitters are you feeding the station with?
Too many stations... 

I have:

2 Anemometer Transmitters. (one for the RM Young via the 6336)
1 T/H Station
1 T/Rain Station (the one with the bad supercap)
1 ISS
1 Temp Station
1 Repeater for the local Marina ISS reception.

I guess that adds up to seven.


Greg H.

[miraculon]

Since the inside cover of the SIM is easy to remove, I inspected the transmitters that were not up on the roof(s). Fortunately, the other three I looked at looked clean with no sign of leakage from the super-capacitor.

2 Anemometer Transmitters. (one for the RM Young via the 6336) (roof mounted-maybe later)
1 T/H Station: Looked Clean - No Leakage
1 T/Rain Station (the one with the bad supercap)
1 ISS: Looked Clean - No Leakage
1 Temp Station: Looked Clean - No Leakage
1 Repeater for the local Marina ISS reception. (roof mounted-maybe later)

I was concerned that others may be on their way to having a bad super-capacitor, but it looks like from this sample the others might be OK. I have a tendency to drop screws and nuts, so I will have to be especially careful when I check the roof mounted units.

Greg H.

[DaleReid]

Greg, I have problems dropping stuff with aging and arthritis in the hands. Not a good time to be a sleight of hand magician I guess.

I also am much more hesitant to go on roofs and climb towers or ladders. 

I solved the problem of dropping stuff by having my dentist magnetize my fillings....