How best to find the "best" small solar panel of a particular size?

[ceech]

Noise isn't bad at all. Surprisingly. It is no bigger than the background noise when no input is connected.

[alexsh1]

@ceech very impressive! I really like:

 It works down to 180mV

the boost to 3.45V works until the board voltage (between pin 5 and GND) goes down to 180mV?

[ceech]

@alexsh1 Yes, the boost converter works down to 180mV. In other words, it can almost completely discharge capacitors.

[alexsh1]

@ceech Which brand of caps you are using?
I may be interested in this board too.

I am currently running your other board with two 10F caps in a test mode with a sensor. Do not have much time for it now, most likely will report in September about my findings.

[ceech]

@alexsh1 Normally I use AVX brand.

[ceech]

Here is a link to openhardware page.

[alexsh1]

@ceech They are very good - I ordered a few myself.

Have you looked at using a flat super caps?
http://sigma.octopart.com/17606633/image/Maxwell-Technologies-PC10.jpg

[NeverDie]

@gohan
If it became an issue, you could turn off the boost converter while doing the radio receptions, and then turn it back on. Unless you were in some sort of continuous receive mode, which would drain things pretty quickly anyway.

[ceech]

@alexsh1 I think they are being discontinued.

[alexsh1]

@ceech all of them? I mean you get the idea. As flat as possible. Size, size and size ...

[NeverDie]

@alexsh1
See if you can find something you like on Digikey. They categorize by active, obsolete, and discontinued.

[alexsh1]

@NeverDie Digikey is good, but too expensive for me. I have to order minimum £33 to have a free delivery.

I still may use them as the search engine only.
Thanks for heads up

[NeverDie]

@alexsh1
yeah, that's what I meant. You needn't buy from them.

[ceech]

@alexsh1 Manufacturers are probably not very keen on making them, since the production costs are higher.

[xgarb]

I've been following this thread and have bought a variety of little panels to experiment with.

These 5.5v 4F 'supercaps' have arrived in the post and I'm not sure how I should test them.

https://www.aliexpress.com/item/2Pcs-ultra-capacitor-5-5v4f-super-capacitor-H-style-For-promotion-Now-Lowest-Price/32571210201.html

For now I would just like to see how well they hold a charge. What's the best procedure to test them?

[NeverDie]

@xgarb
I wish there were standard tests that were widely used, but there don't seem to be. You might try holding it at its rated voltage for 72 hours, then remove power and check its voltage after 24 hours with no charging to get some idea as to what its leakage is. These tests only mean something if you compare them against a capacitor that you like though. Then maybe it will tell you whether it's better or worse.

The only test that really matters is how it performs in your use-case.

[gohan]

@xgarb I have them too, I tried and there is definitely leakage but it should not matter much as the sensor will not have to stay for days without charging

[gohan]

https://www.tindie.com/products/MadElectronEngineering/infinity-solar-bank-v401/

Just another option. Quite expensive though.

[NeverDie]

@gohan
Looks like an interesting approach for a 6x 400F solution. The individual capacitors alone aren't cheap, so I guess it's priced in reference to the total BOM cost.

[gohan]

You are buying the board only, you have to buy the supercaps separately