Powering T-Beam with 5V solar panel or external power bank


There has been a few similar discussions on the same topic from 2022. I am wondering if T-Beam V1.2 would change much for external power source options.

Scenario 1: Has anyone tried powering the T-Beam directly from a regulated 5V solar panel by connecting to the power input? The thinking is that the solar panel will power the T-Beam during daytime and when light dies down, the onboard 18650 will power throughout the night. I do not believe the T-Beam can re-charge via solar like RAK does. But if this works, it will extend the operational time of T-Beam.

Scenario 2: Has anyone tried powering the T-Beam from an external power bank? The idea is similar to Scenario 1 with the intention to extend its operational time. The question is, will the onboard 18650 kick in when the external power bank runs dry.

Thank you!

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the 18650 will take over for a running T-beam when external power fails - you can verify that by pulling out the USB cable. Your problem may come when the 18650 runs down past the point the the power management (on the newer T-beams > v0.7) pulls the power.

I don’t think it will restart on its own even if you apply external power and/or the 18650 gets charged up again. You have to press the power on button to start it up.


I have just tried on a T-Beam 1.1. It starts up from the off state when you apply external USB power, both with the battery fitted (but charged) and without the battery, so your use case may be OK. I haven’t tried applying external power into a T-beam with a flat 18650, however.


i had a t-beam on my roof, running on solar for some time.
it was a 6V 3A connected to USB input via a 5V buck-converter.
i did remove the onboard 18650 connectors and connected a 5000mAh 26650 by some wire.
that worked , but i did not like the big solarpanel and ched the setup to a rak4631 that only needed a 1 W Module.

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Thank you! I dont expect the T-beam to run like RAK4631, which I have one set up for solar powered. T-beam is much more compact in size and easier to deploy for a short period of time. A possible user case can be swapping out the external power bank periodically to ensure continuous running.

Thank you! I can try connecting the T-beam with external power bank which connects to a solar panel. The power bank will act as the main power supply and periodically recharged by solar; the onboard 18650 will function as the back-up power. When needed or when the main power bank is low on power, swapping it out is much easier than taking out the onboard 18650 battery.

that will depend on the powerbank… some models switch off power, when there is no current going… so maybe it will switch off USB power when the 18650 is fully charged… maybe it will function, maybe not :slight_smile: you will need at least 20 Wp solar power (getting alot of direct sunlight!!) to keep the esp32 powered !

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Taking the guess work out of the equation: V25 USB Battery Pack | 6,400mAh 23Wh

Does anyone know other brands of power bank that is capable of Always on?

once again, spending 30 on powerbank, another 50 on solar.
you would be much cheaper and more easy and smaller with a RAK wireless / or T-echo device, consuming about 1/10 of the energy than an esp32
you spend 20 more for the device, but it will run endlessly with a simple 18650 or pouch Lion battery and 1 Watt solar. the rak device even has its own solar controller (solar maximum 5V!)

have a look at this: this is solar panel and battery in the box already for less then 10€ :wink: you just need to get a Rak wireless device.

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Absolutely agree! It is more of a supply issue of getting a RAK at the moment. In the meantime I am sitting with several idling T-beams and Heltec v3.1.

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