TTGO LORA32 minimum voltage on 5v in

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I have a 5V nominal solar panel I want to try to use for a repeater deployment with a Lora32 board + 18650. However on a dark rainy day like today, the voltage sags to as low as 3.95v. How does the board behave with that low of a voltage into the 5v pin? I guess I could put boost circuit in front of it, but I’m curious if anybody has hooked any of the versions of this board up to bench power supply on the 5v and ground to see just how low it can be usable on those pins.

Even if it doesn’t sustain enough voltage to charge the lion cell, it would be swell if it at least could keep the board from pulling a load from the cell while sleeping or better yet keep the board operational during a duty cycle. I may do some experiments here but I was curious to see anybody else had done them first.

Thanks

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I did a quick-n-dirty test and I’d say 3,7 V is the threshold for reliability. Anything below that and the board will endlessly reboot. No surprises, as I believe the board itself runs at 3,3 V, so you have to take into account the voltage regulator dropout.

PV panels really call for MPPT and a step-up/down regulator. It might be overkill, but to ensure reliability I’m building a node with a 10 W, 20 V panel, MPPT, charger/regulator and batteries.

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Can you read the part number of the voltage regulator on that board? If you can read it out, I can look up the specs for you.

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