Can one use battery modules for solar energy storage?

[Wilou1428]

I'm considering using these battery modules for energy storage:

https://www.energusps.com/shop/product/li-ion-building-block-with-temp-sensor-3-6v-20ah-18c-discharge-37

and I want to charge them using solar panels what kind of difficulties should I expect? or isn't there nothing to worry about?

[Mike90250]

expect problems.
You will need a Charge controller, and an understanding of how to balance and charge the batteries without damaging them, There is a LONG thread in the LiIon battery forum about ways to charge and discharge LiIon batteries.
I think I would wait before you buy anything, read a lot here first and ask questions, and know that batteries and solar power always costs more money replacing batteries than you save by harvesting power.