@neverdie Yep, I had the same experience with this LTC3108 breakout.
I also intended to try the following modules which have a ton of functionality baked in. Unfortunately, they multiply the cost of a basic node by 2-5x.
From an energy harvesting perspective, I think rechargeable watch battery + 0.2F super cap + 4 100uf is my favorite setup. Cheap, fault tolerant, very small profile if you use 1206 ceramic capacitors (not shown in this prototype). Based on this design: https://www.allaboutcircuits.com/technical-articles/overview-of-the-ble-solar-beacon-from-cypress-semiconductor/
0.2F 3.3v Capacitors
3v Rechargeable Battery
1206 100uf Capacitors
Cheapest amorphous, indoor solar panels I have found: 2.7-3v
Tiny S4 1N5817 Diodes