ESP8266 Community Forum

- Tue Sep 22, 2020 9:05 pm #88848 Hello,

I am having an issue adding a 5v step-up module to power some WeMos D1 mini. It will be used with solar panel battery charger.

It is constant ~5v (5v - 5.6v) until I connect it to the WeMos 5v pin. Then it drops to ~1.5v (1.1v - 1.3v). When I disconnect it from WeMos 5v, it backs to 5v. (see attached images)

At this point, there is no sketch running on WeMos. I already tried to replace the step-up module, even with other manufacture.

I am lost...

Any ideas?

Thank you,

Gerson Garcia.

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- Wed Sep 23, 2020 11:10 am #88857 Your solar panel is probably not able to deliver the needed current (±350mA for the ESP and ±250mA for the other components on a WeMos, apart from the losses in the step-up convertor).

There are lot of solar powered projects on the internet (almost) all of them use battery power a primary source and solar to charge when there's enough sun, just do a search on Instructables, Hackaday, but also here.

Also these projects are mostly optimized to use a plain ESP8266 without additional/unneeded components and a convertor that's directly able to supply the needed 3.3V by the ESP (instead of first up-converting and then down-converting again, resulting in a lot of loss in power).

Assumption is the mother of all f*ckups. At least: that's what I'm assuming.

- Wed Sep 23, 2020 11:30 am #88859

Your solar panel is probably not able to deliver the needed current (±350mA for the ESP and ±250mA for the other components on a WeMos, apart from the losses in the step-up convertor).

There are lot of solar powered projects on the internet (almost) all of them use battery power a primary source and solar to charge when there's enough sun, just do a search on Instructables, Hackaday, but also here.

Also these projects are mostly optimized to use a plain ESP8266 without additional/unneeded components and a convertor that's directly able to supply the needed 3.3V by the ESP (instead of first up-converting and then down-converting again, resulting in a lot of loss in power).

QuickFix, I know the solar panel will be able to charge the battery, I have a similar device running it now. I am trying to use different solar panel/charger controler that is cheaper. I am not there yet. I am connecting the solar panel module on USB (as you can see in the picture) and it is generating the correct amount of power (4v and some) to the step-up module.
My problem is from the 5v step-up to nodemcu. When connected, the power on the bus go to ~1v and never power it.
Thank you.

- Thu Sep 24, 2020 8:25 am #88869 Power (P in Watt = W) is electric potential difference (U in Volt = ) times current (I in Ampere = A) or P = U * I (sometimes written as P = V * I in some regions).

Your solar panel might be able to give you the desired 5V, but how much current (I in Ampere) can it provide?
If it's not able to provide the needed ±500mA needed by the Wemos + the current needed (as loss) by the convertor, the current becomes too high and the voltage will drop like a brick.

You can connect your DMM in series of the power supply, set it to measure current and use a potentiometer as a load to see what the maximum current is, the panel is able to supply.


I've taken above image from this website, describing how to determine the maximum power a solar panel is able to deliver.

Last edited by QuickFix on Fri Sep 25, 2020 6:14 pm, edited 1 time in total.

Assumption is the mother of all f*ckups. At least: that's what I'm assuming.