Hi, since the beggining of the game when I try to recharge my shield it always reaches 1/4 total and than won't go higher.
Is this a bug or did I just miss something?

The current shield generator you have doesn't go higher than 25%.
You'll find another shield generator that can charge up to 50%, and eventually you'll find the 'Graviton' (iirc) shield generator that will be at 100%.

In other words: Working as intended. :)