I bought a Dell Inspiron 5570 about a month ago, and I'm worried that if I play games on it, while having it plugged in at all times will decrease the battery life significantly.
I use the AMD graphics card on all the games I play, so the laptop gets hot quickly, and the fans start to get loud, which isn't that annoying, but I'm only worried about the battery and if it's safe to keep the laptop plugged in even when it's fully charged.
Thanks in advance.
There are a lot of things batteries don't like, but draining them by using them is actually the worst. Keeping a battery topped up creates far less wear, so don't disconnect from the AC adapter and run on the battery unnecessarily. However, if your BIOS has certain options and you're willing to accept some other tradeoffs, you can do even better in terms of wear than keeping it topped up.
Other things batteries don't like include being drained all the way to the bottom (so don't wait until the last moment to plug an AC adapter back in) and being held at maximum charge all the time. On the latter point, again that's still better than actually draining the battery with use, but some systems have BIOS options that allow you to set your maximum charge level to 80%, for example. That will improve the long-term life of your battery significantly, but of course you're also giving up 20% of its capacity most of the time, except for cases where you might manually set it back to 100% temporarily. Incidentally, Tesla cars default to only charging up to 80% unless you specifically select a Max Range charge, which deliberately cannot be set as the default, for exactly the same reason.
And best of all would be to not keep the battery topped up to any particular level at all, which can be achieved if your system allows you to also specify a MINIMUM charge level. On my XPS 15 9530 for example I have my max charge set to 80% and my minimum charge set o 50% (the lowest it would let me go). So when my system is plugged in, it charges the battery to 80%, then it continues running on AC power but does NOT keep the battery maintained at that level. Instead, the system allows the battery battery to self-discharge down to 50%, which takes several days, and only then does it charge the battery back up to 80%. That strategy means the battery spends the least time of all accepting current, and therefore incurs the least amount of wear. The downside to this strategy of course is that if I ever need to disconnect my system from the AC adapter unexpectedly, I may only have a 50% charge, but I pretty much only take my laptop anywhere when I'm traveling. Otherwise, it sits on my desk.
As you may have already concluded, pretty much anything people actually want to use batteries for creates wear on them, and reducing long-term wear involves giving up day to day convenience. You just have to decide which is more important to you.