What is the minimum current for charging a battery?

Okay, so charging batteries... it's kinda tricky, right? I mean, I've learned the hard way with my campervan batteries (AGM, the good stuff). You need a decent amount of current. I usually go for, like, 15-25% of the battery's capacity, at the very least. So, say I have a 100Ah battery, I'm aiming for at least 15 amps, ideally closer to 25. But, here's the thing...that's just to charge it, you know? What if you're still using stuff? Like, what if I'm running my laptop and the lights while trying to charge? You gotta crank that current up! Otherwise, it's like trying to fill a leaky bucket – you're putting something in, but it's also going out! It's not really charging, and, honestly, I've heard it can even damage the battery long-term, which is not good. Remember that time we were at the campsite, and I forgot to account for the fridge draining the battery? Nightmare! Lesson learned. So yeah, sufficient current is key, but even more so if you're using power at the same time. It's not just about charging; it's about charging plus whatever else is drawing power. Make sense?