Solar Power Supply

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Ton_vN
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Re: Solar Power Supply

#101 Post by Ton_vN » 06 Oct 2021, 10:58

Some extra protection also helps.
Can be very simple: limited capacity, but have technically positive experience
;-) WAF is very low,therefore should be applied 'outside public view', but construction is effective:
a simple, perspex shield as protection above, also offering sufficient space for ventilation.
Last edited by Ton_vN on 08 Oct 2021, 10:19, edited 3 times in total.

TD-er
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Re: Solar Power Supply

#102 Post by TD-er » 06 Oct 2021, 10:59

That's for sure not going to win a designer award :)

seb82
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Re: Solar Power Supply

#103 Post by seb82 » 08 Oct 2021, 18:04

Ton_vN wrote: 06 Oct 2021, 09:24 Then question better phrased: how to prevent for next install?
I experienced the same. Now, I put the solar panel inside a plastic box with a transparent cover. The cover might also become blurred, but it is a lot less affected and easier to clean and/or replace.

I guess output is somehow decreased - though I did not test how much - but it was still sufficient for my project to run.
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Re: Solar Power Supply

#104 Post by TD-er » 08 Oct 2021, 20:40

Decrease in efficiency can be explained by reflection of the plastics and probably also higher temperature inside the box.
Typically the efficiency drops by 0.5% per degree C.
Losses due to reflection are a lot harder to predict as it also depends on the wavelength etc.

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Re: Solar Power Supply

#105 Post by Ton_vN » 10 Oct 2021, 16:37

Earlier in this thread already reported bad experience with panel-in-box getting (over)heated.
'Open air' installation is preferred to keep the panel cool & happy for energy-production.
Shielding by a perspex plate at small distance above the panel will keep off rain & snow, but moisture will still be a pain.
Especially condensation has unpredictable ways of appearance.
As TD-er describes, none of these protective measures will help against effects of bad construction: :( quality has a price-tag ......
Last edited by Ton_vN on 12 Oct 2021, 12:24, edited 4 times in total.

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Re: Solar Power Supply

#106 Post by TD-er » 10 Oct 2021, 17:17

You can also leave the bottom open.
And slightly higher temperature will automatically lead to lower (relative) humidity.
Still, bad quality is impossible to turn into "good quality" by these measures.

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Re: Solar Power Supply

#107 Post by Haldi_2 » 03 Nov 2021, 21:11

for 25$ you can get a 4W Solar Panel with space for 6x 18650 Batteries and 5V Output. Waterproof.
https://www.aliexpress.com/item/1005002 ... 478ciB31CY
H8b3c340b04114447adfd0b660791f39aa.jpg
H8b3c340b04114447adfd0b660791f39aa.jpg (94.33 KiB) Viewed 5869 times

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Re: Solar Power Supply

#108 Post by TD-er » 03 Nov 2021, 21:43

Not sure if having lithium cells in a black enclosure without vent holes, is a very good idea.
Especially if you place it in such an orientation where it may get the most direct sunlight.

I guess it is probably a translation issue (also I really wonder why AliExpress keeps resetting my preference to whatever random language or currency)
FAQ:

1. de zonnepanelen op de markt hebben een garantie van slechts 3 maanden, maar de zonnepanelen breken na een paar maanden en kan niet worden opgeladen. Koper feedback is niet duurzaam.
Translated from Dutch to English:
"1. The solar panels on the market have a warranty of only 3 months, however the solar panels will break (crack) after a few months and cannot charge. Buyer feedback is not durable"

Not sure if a FAQ like that will persuade me into buying these :)

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Re: Solar Power Supply

#109 Post by Ton_vN » 04 Nov 2021, 10:25

Also stating that an MC-cell has 23% efficiency is 'rather' optimistic (for that price-tag).

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Re: Solar Power Supply

#110 Post by Ton_vN » 12 Nov 2021, 13:27

Soilthermometers now under test, have the impression that the reducing lightinput at this time of the year starts to cause dips in the solar-powered supply.
As a twist to Shardan's suggestion, at the output of the solar-fed TP4056 fitted a DCDC_Booster to get continous 5VDC as long as sufficient input from that TP4056.
Cannot quantify, but have the impression that WEMOS likes to have 5V as input, if only to keep it's 3V3-line steady for the 'internals' and for the attached sensors and auxiliaries.
Booster3V5V
Booster3V5V
Booster3Vnaar5V.png (195.78 KiB) Viewed 5725 times
steady.

Matthias
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Re: Solar Power Supply

#111 Post by Matthias » 09 Jan 2022, 19:03

Hi,

I want to connect my wemos to a solar panel.
I will have a single 5V / 10W (2A) panel.
Which diode should I put between the positive of the solar panel and the TP4056? Thanks in advance ?

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Re: Solar Power Supply

#112 Post by TD-er » 09 Jan 2022, 19:20

A very standard 1N4007 or something similar would be my first choice.

Matthias
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Re: Solar Power Supply

#113 Post by Matthias » 09 Jan 2022, 19:22

Could you say me how you choose a diode ?
There is lot of informations in the datasheet.

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Re: Solar Power Supply

#114 Post by TD-er » 09 Jan 2022, 19:37

The iN4007 I mentioned is for upto 1A.
Strictly speaking the max. current the panel can deliver is 2A (10W/5V), but I don't think that will be used as it doesn't make sense to have a device connected which will consume the max. current the panel can deliver for only a few hours on a very sunny day.
So I guess you hardly will use more than a few-100 mA and then it makes sense to use a diode capable of 1A.

The other relevant parameters are:
- Max voltage (not really interesting in this use case as almost all diodes can handle 50V at least)
- Voltage drop
- How quickly a diode may switch (Schottky diodes are known for their fast switching, not really relevant here)

So the only relevant parameter for this use case is the voltage drop, which is roughly 0.6V for the diode I mentioned.
You could choose for one with a lower voltage drop, but most of those cannot handle larger currents.

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Re: Solar Power Supply

#115 Post by Matthias » 09 Jan 2022, 19:40

Thank you for these explanations.
You say Schottky diodes are not ideal for this project.
Which diode should I choose?

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Re: Solar Power Supply

#116 Post by TD-er » 09 Jan 2022, 19:53

No, not that it is not ideal, just that the faster diode switching speed is not needed here.
It doesn't hurt if you have a faster responding diode.
Another pro argument to use a Schottky diode is that is does have a lower voltage drop.
An argument against such a diode is that it does have a larger leak current.
I am not 100% sure what is an acceptable leak current towards a solar panel.

If you want a Schottky diode, capable of handling 1A, then you can pick for example a very standard 1N5817


The lower voltage drop can be quite useful when using a solar panel as it may allow for longer operation at low solar radiation.
But as I said, I don't know what effect a small leak current has on the solar panel.

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Re: Solar Power Supply

#117 Post by TD-er » 09 Jan 2022, 19:59

I just searched for the main purpose of the blocking diode for a solar panel and it doesn't seem to be for protection of the panel, but only for preventing any connected battery to discharge via the panel.
So given it is put in front of a DC/DC board, it probably doesn't matter to have a very small leak current.

One other thing you may need to realize is that the voltage given by the solar panel is mainly proportional to the current.
The open voltage is -somewhat- the max. voltage you may expect. The only factor is the temperature of the panel. The voltage generated by the panel is higher at low temperature.

You should also consider using some battery to be charged. Only operating on a solar panel is not going to work well as its output is too variable.

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Re: Solar Power Supply

#118 Post by Matthias » 09 Jan 2022, 20:25

Here is the assembly that I could see on the net.
But I can read some malfunction in the comments.

In my case, i use a wemos D1 mini.

Image

https://randomnerdtutorials.com/power-e ... onitoring/

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Re: Solar Power Supply

#119 Post by TD-er » 09 Jan 2022, 21:08

Just looking at the image you posted, I would suggest to use 1 diode each per solar panel and not connect both panels in parallel like suggested in the schematic drawing you show.
If one of the panels is in the shade, it will draw current from the other one.
Thus effectively doing worse than when using only 1 panel.
Also it may cause issues on the shaded panel if it draws a current instead of outputting.

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