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Hi,

I need to provide my launchpad with solar panel energy harvesting with 500F supercapacitor. 50 - 100 ma charging current is sufficient and the solar panel provides 2.5V.

 

input voltage 0.5 - 3 volt

output voltage 3 volt

 

Any suggestion about the voltage regulator to be used?

Thanks. 

 

If you're committed to the boost converter with MPPT, then a small Li-Ion is a way better storage unit than a supercap is.  There is a sweet-spot around 70mAh, because these are used in a lot of bluetooth headsets and FitBits and things like these.  You can find these on aliexpress for really low prices, but you can use Powerstream if you want a US distributor who has English datasheets.  At least use powerstream for the datasheets.

 

http://www.powerstream.com/li-pol.htm

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If you're committed to the boost converter with MPPT, then a small Li-Ion is a way better storage unit than a supercap is.  There is a sweet-spot around 70mAh, because these are used in a lot of bluetooth headsets and FitBits and things like these.  You can find these on aliexpress for really low prices, but you can use Powerstream if you want a US distributor who has English datasheets.  At least use powerstream for the datasheets.

 

http://www.powerstream.com/li-pol.htm

I plan to design durable wireless sensor node that long-lasting (many years) without any maintenance, so I prefer to use super capacitor instead of rechargeable battery. There is no problem with storage capacity because the sunlight is available almost all days throughout the year in my country. 

 

Low price solar panel with a variety of output voltage are available now. So, I can either using step-down voltage regulator with 5V solar panel or using boost voltage regulator with 3v. I have no experience about which one is preferred in my case.

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I plan to design durable wireless sensor node that long-lasting (many years) without any maintenance, so I prefer to use super capacitor instead of rechargeable battery. There is no problem with storage capacity because the sunlight is available almost all days throughout the year in my country. 

Let's say you use the BQ25570, you run your Vdd at 2V, and your mean power is 1mW.  This means your charge cycle is about 10 days, with a 70mAh LiPoly pack.  You are charging at <0.5C.  The Li-polys are rated for 10% capacity degradation after 300 charge cycles at 0.5C, which in your case equates to 8 years.  LiPoly cells degrade more rapidly when they are charged or discharged at high amperages, which you are not doing.

 

More importantly, you need to worry about heat.  I bet it gets hot in the desert.  Both supercaps and LiPoly cells are sensitive to heat.  You should look into this.

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Low price solar panel with a variety of output voltage are available now. So, I can either using step-down voltage regulator with 5V solar panel or using boost voltage regulator with 3v. I have no experience about which one is preferred in my case.

Boost is easier.  At night the panel will be low-voltage.  At dawn it will increase voltage.  If you use a low-voltage solar cell, then you can keep the entire voltage range in the boost regime.  This is easier than buck-boost and more efficient.

 

I designed a WSN device using a 1.9V solar cell.  In maximum California-summer sunlight it was 1.8V.  Indoors next to a window it was between 0.4-1.0V depending on the time of day.  With office lighting, it was between 0.2-0.8V.  The point here is that the whole voltage range will be observed during the operation of the device.

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Boost is easier.  At night the panel will be low-voltage.  At dawn it will increase voltage.  If you use a low-voltage solar cell, then you can keep the entire voltage range in the boost regime.  This is easier than buck-boost and more efficient.

 

I designed a WSN device using a 1.9V solar cell.  In maximum California-summer sunlight it was 1.8V.  Indoors next to a window it was between 0.4-1.0V depending on the time of day.  With office lighting, it was between 0.2-0.8V.  The point here is that the whole voltage range will be observed during the operation of the device.

Good vindication, but I thing you forget something important, I'll use these nodes in outdoor throughout the city and after a while the dust might degrade the performance of the solar panel below the threshold of operation. So I hesitated before going ahead with this option.

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Good vindication, but I thing you forget something important, I'll use these nodes in outdoor throughout the city and after a while the dust might degrade the performance of the solar panel below the threshold of operation. So I hesitated before going ahead with this option.

Do a test.  It should be quite easy.  You will want to do the test with the MPPT controller attached. 

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Do a test. It should be quite easy. You will want to do the test with the MPPT controller attached.

I would trust @@jpnorair he has a lot of experience here.

 

Noting better than building it and testing it, only then will you know what are real problems vs worries that never happen.

 

Engineers in pursuit of perfection do a lot of worrying, brave engineers get stuff done.

 

 

Sent from my iPhone using Tapatalk

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