jremington:
The short circuit current for the panel you linked (with zero volts across the cell) won't be much more than 100 mA.
Thank you a lot for your useful comment! Alright, I've looked a bit more online and I will probably go for following circuit:
from: https://www.electronicshub.org/solar-battery-charger-circuit/
I have also thought about going for this circuit:
from: Solar Charger Circuit using IC LM317 | Electronics Project
However, I don't see a reason for putting a Zener diode and a transistor that sucks away the current if the Zener didoe breaks down. I think the R1 and R2 resistors of the LM317 can be selected to give a very steady output voltage.
In my case, I want to charge three LSD NiMH batteries with a rating of 1.2V:
I will wait for their arrival, fully charge them and see the actual voltage and then select the resistances for the LM317:
What do you think? Is that circuit smart and efficient enough? I don't want to waste the solar energy.
Best,
Marco