Apparently I needed to learn yet another lesson.
Please see this older post regarding the first battery that I installed, and the little struggle that I had to begin with: Let there be light
The old battery drained however faster and faster as the days went by, and after a while I couldn’t even charge it. It was completely dead.
I therefore decided to buy another one, but this time one with a bit more power.
This model has more than twice the amperage of the old original stock model, 4.5 amps vs. 2.1 amps, so should be a nice little upgrade. It’s sealed as well, so no risk of any acid leaking.
Cut the wires from the old battery and reused those, and mounted some cable shoes, and that was about it. It holds a nearly full charge after approximately 1 month, and haven’t run once yet.
I reckon that the old battery simply just was in a poor condition, maybe even from the get go.