I agree with Airi. Without stating what weapon (s) you use, it's a bit hard to give a good strategy.
As a fellow Charger main myself, I can tell you that mobility is always key. Never stay in one spot or walk in inkling form when confronted with us. That just helps us gain an easier shot. Switching between inkling and squid form while moving around will usually always catch us off guard. My aim is steady, and even I have trouble aiming if my opponents move around a lot (just don't be predictable with your movement).
Going against chargers myself, some aren't always aware of their surroundings. Can't tell you how many times I've snuck up behind enemy chargers and splatted them. If they're focused on your teammates, you have a better chance at maneuvering around them and/or splatting them. Try and always pay attention to see which chargers your opponents are using before the match begins, so you know how out of range you have to stay. The Eliter 3k is much harder to avoid because of its massive range, but stay mobile and even they will have trouble getting you.
Yes, we aren't really good close range, but be careful while approaching as well. I've splatted plenty of people for underestimating me up close, or not seeing that I have my special and get splatted by my bomb rush, or just a good placed splat bomb. So even when close, be sort of wary. When confronted, we have the choice of either retreating, trying to fully charge splat you, or harass you with uncharged shots (which can still splat you if we hit you a decent amount of times).
When echolator is activated...please don't try to sneak around us or anything as we can clearly see you. Use cold blooded to shorten the time it's on you, or just stay out of our range as when even in squid form and hiding in ink, we can still track you down. Hiding under the ledges we're on, we usually can't reach you without moving, or throwing a bomb, so you're free to harass us from there until we retreat and back off, or you splat us.
Also, be sure to not solely focus your attention on chargers, or you just may get splatted by our teammates more than us as your view is completely on us, and not your surroundings.
Didn't mean to make this post so long...but I hope this helps you even a little bit.