Author Topic: How to test Super Cap?  (Read 1759 times)

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Offline dalecoy

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Re: How to test Super Cap?
« Reply #25 on: October 23, 2018, 12:31:04 PM »
The SIM was powered today by the new solar panel + new supercap (but no battery) and was transmitting most of the day during the sunlight hours (from about 9am until 5:30pm).  When I arrived home around 6pm, it had died already.

First I disconnected the solar panel and measured the voltage on the supercap, 0.9V.   Then I shorted the cap's legs temporarily to discharge it fully.

0.9V - so not enough to run the transmitter.  And unless you shorted the supercap for quite some time, that did not "discharge it fully".  That would take quite some time. 

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Next I used crocodile leads to connect up the battery in series with the Ammeter.   For the first 40 sec or so, the current went from an initial 180 mA to a max. of 300 mA and then eventually to 0 A.   After that initial rush (which I assume has to do with charging up the supercap?) there was about a 40 sec period of no draw after which it started with repeat cycles of +/- 12 sec on, then 12 sec off.   During the on cycles it drew 20 mA which seems to correlate roughly with Davis' stated consumption of 14 mA.   Even after disconnecting all the sensors, the consumption behavior and values remained the same.

That's not normal.  There should not be any long period of current (20 ma).  There should be brief (milliseconds) periods of current draw, every 2.5 seconds.  You would not be able to tell how much current with your meter, because of the brief pulse.  So, that's indicating a problem.  Or two or three.

And the battery does not charge the supercap.

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With the battery connected, the voltage across the supercap would not exceed 0.92 V. 

Because the battery doesn't charge the supercap, and you didn't discharge it fully - and anyhow, why did you do that?

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This seems to indicate that my SIM board probably has an issue with charging up the supercap rather than an issue of excessive consumption, right?   (I guess I must be one of the unlucky ones as Johnd had mentioned earlier). 

I don't agree with your conclusion.  Your SIM board is not working properly.  It has excessive current draw.  This has nothing to do with charging - except that the current draw prevents the solar panel from charging the supercap during the day.

And no, I don't have a clue what component(s) you might need to replace on the SIM board.

Offline JudinNorman

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Re: How to test Super Cap?
« Reply #26 on: October 23, 2018, 12:39:17 PM »
Probably good reason the previous owner wanted to get rid of it. After the time and money spent trying to fix this, a new Sim board would have been better option.
It's a throw away society today for most electronics. Stuff just can't be fixed, rather made to fix anymore.

Offline dalecoy

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Re: How to test Super Cap?
« Reply #27 on: October 23, 2018, 01:48:37 PM »
Probably good reason the previous owner wanted to get rid of it. After the time and money spent trying to fix this, a new Sim board would have been better option.
It's a throw away society today for most electronics. Stuff just can't be fixed, rather made to fix anymore.

AA1ZA's SIM board could be fixed.  For a professional engineer with professional equipment, I would guess somewhere between 30 minutes and 1.5 hours to diagnose (at perhaps $80/hour shop charge), then order the part(s), wait a few days to receive them, and then replace-and-test (another .5 hours at $80/hour).  And that $80/hour is probably low.  And the time estimate to diagnose ASSUMES that the engineer already has some knowledge of the correct functioning of the board.

Offline AA1ZA

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Re: How to test Super Cap?
« Reply #28 on: October 23, 2018, 04:12:48 PM »
Thank you for the comments and input.   I appreciate it.

I just got off the phone with the support guy at Davis.   I'm afraid no definitive answers. 

I asked whether it's OK to run a wireless SIM without battery and expect its supercap - if all is good - to keep the SIM powered through most the night.  At first, the answer was 'yes' and then somewhat later in the conversation there seemed to be doubts as to whether there might be some or other software check built into the design to ensure that there's a battery installed... (Given all the confirmation I got here already, I think I'll go with his first hunch on this one though).

Then I asked whether the three sources (solar panel, supercap and battery) were all connected in parallel, to which he answered,"No, there's a distinct handover from the one source to the next, as and when required".

Lastly, I asked about the 12 sec on; 12 sec off transmissions and he said it didn't sound normal, but couldn't say for sure (he would need to ask one of their engineers).    Anyhow, I checked up on the manual and the outside temperature updates at an interval of every 12 sec.   It is the wind speed and wind direction that update every 2.5 sec.   Since there was no air movement last night when I tested, I wonder if the absence of those sensor inputs may have affected the duty cycle of the transmitter in any way... ?   (Just a wandering thought that's worth checking it out again tonight, I guess).

Also last night, I received my TP-Link router in the mail, flashed it with the Meteobridge firmware and have been updating the PWS Weather site successfully at 1 minute intervals ever since 2 am this morning (the SIM is running on a battery + solar at present).  The readings seem to correlate with those of nearby stations.

So I guess I need to decide whether I should dump a circuit that behaves like this or not.   Apparently Davis also offers a $60 RMA on the SIM board - so that opens up another option besides the $18 option of a PSU powered SIM.

(I realize that I come across as maybe stingy on this issue, but enjoying on a single income the luxury of a hobby such as this, in parallel to annual family health care expenses that ranges 20% to 30% of gross, one (sort of) has to be...   ;-)   Thank you again for all your valuable input!)   
Davis VP2 > Envoy+USB logger > Meteobridge;

Offline rdsman

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Re: How to test Super Cap?
« Reply #29 on: October 23, 2018, 04:31:11 PM »
My ISS with no battery and a bad supercap runs about 3 minutes in the absence of sunlight!

I still want to know if anyone knows what IC U14 on the ISS board is......

Ray

Offline dalecoy

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Re: How to test Super Cap?
« Reply #30 on: October 23, 2018, 05:31:33 PM »
AA1ZA, why not go ahead and test powering the SIM externally?

And is your data now available for us to see?  Somewhere?

Offline brett c

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Re: How to test Super Cap?
« Reply #31 on: October 23, 2018, 05:48:49 PM »
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With the battery connected, the voltage across the supercap would not exceed 0.92 V.

I don't believe that the battery charges the supercap in the VP2.  I have proven this with the Vue ISS.  I think you need to look at the voltage on the supercap in full sunlight.  Can someone tell me what the IC in the red circle in this picture is?

Without being able to see the Full ID of that chip, it looks to be a voltage regulator.

Offline rdsman

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Re: How to test Super Cap?
« Reply #32 on: October 23, 2018, 05:57:16 PM »
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Without being able to see the Full ID of that chip, it looks to be a voltage regulator.

That is why I am hoping that someone that owns one of these can help me out.  I don't have one, just a picture and a poor one at that!



Ray

Offline AA1ZA

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Re: How to test Super Cap?
« Reply #33 on: October 23, 2018, 11:25:53 PM »
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That is why I am hoping that someone that owns one of these can help me out.  I don't have one, just a picture and a poor one at that!

They painted the PCB with some kind of resin.  On my board that IC is covered so thick that there are even tiny bubbles embedded, making it impossible to read anything off of the top of it.   
Davis VP2 > Envoy+USB logger > Meteobridge;

Offline dalecoy

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Re: How to test Super Cap?
« Reply #34 on: October 24, 2018, 12:04:41 AM »
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That is why I am hoping that someone that owns one of these can help me out.  I don't have one, just a picture and a poor one at that!

They painted the PCB with some kind of resin.  On my board that IC is covered so thick that there are even tiny bubbles embedded, making it impossible to read anything off of the top of it.

That's to protect it from the weather, which (of course) makes sense. 

Offline AA1ZA

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Re: How to test Super Cap?
« Reply #35 on: October 24, 2018, 12:14:20 AM »
AA1ZA, why not go ahead and test powering the SIM externally?

And is your data now available for us to see?  Somewhere?

You should be able to see my logged data of today on pwsweather.com if you searched for station, 'AA1ZA'.   It ran from 2 am until about 6 pm when I took it off the air again for further testing.

First things first:   I think you were dead on when you said earlier that I didn't seem to have a charging problem, but rather an excessive current draw issue.   

Today the station enjoyed much better radiation and this evening I managed to catch it just before sunset.  I set off to measure the supercap voltage first and it was sitting at a healthy 2.35 V.   From the time that I disconnected the solar panel until the supercap was drained down to 0.5V, was maybe just over 30 mins.   I could literally see it "bleeding to death"...

Then it dawned on me:  My misjudgment of the decimals!   I drew an incorrect conclusion based on an assumption that the 20 mA cyclic draws that mine exhibits, correlated with Davis' stated specs.   That is not the case.   Davis actually said, 0.14 mA (140uA); not 14 mA...  which means that that's a totally different story then!   I sure do have a serious current draw issue at hand...

With that, I looked the board over one more time and noticed two other electrolytic caps (the last of the DIY repairs that I was still willing to attempt).   I replaced those too, but alas, to no avail - it still did the same thing...

Having a better appreciation now for the magnitude of excess current that mine draws, I'm not so sure anymore about turning a blind eye to the problem by simply throwing external DC at it.  I think I should rather bite the bullet and send it in for an RMA repair.   (That would put me $285 in total into the deal to date).

EDIT:  Btw, while I was at it this evening, I flicked the 4th DIP switch and the LED did blip around every 2.5 secs.
« Last Edit: October 24, 2018, 12:43:38 AM by AA1ZA »
Davis VP2 > Envoy+USB logger > Meteobridge;

Offline dalecoy

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Re: How to test Super Cap?
« Reply #36 on: October 24, 2018, 10:02:24 AM »
Glad I could help, and thanks for confirming my SWAG!

Offline AA1ZA

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Re: How to test Super Cap?
« Reply #37 on: October 24, 2018, 11:39:17 AM »
No SWAG, Sir.   

Experience.  I can tell.   

Thank you again!
Davis VP2 > Envoy+USB logger > Meteobridge;

Offline rdsman

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Re: How to test Super Cap?
« Reply #38 on: October 24, 2018, 11:40:24 AM »
Perhaps other people can learn something from your time and effort......

Ray

Offline AA1ZA

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Re: How to test Super Cap?
« Reply #39 on: October 24, 2018, 02:15:47 PM »
This forum and its contributors are great!   

If nothing else, this thread just saved me from inserting a new battery, mounting the ISS up a 21 ft pole, firing up a host weather services and then 12 days later... (according to my new calculations), having had to yank it all down again due to a retired battery and night time loss of services...    UU
« Last Edit: October 24, 2018, 02:39:33 PM by AA1ZA »
Davis VP2 > Envoy+USB logger > Meteobridge;

 

anything