Preserve Laptop Battery Life Span When Plugged In Always?

Hey all. I mentioned I got a new laptop battery for my dell xps 15 9550 which is an old machine for many years. Now with this laptop and previous laptops I had, I use it mainly as a desktop... connected to an ac charger and connected to external monitors. Pretty much im plugged in almost always.



Previously a while back what I did was with an older laptop before it went bad... charge it till 100%... then unplug it and do my thing... till it hit around 30% battery or so... then charge it again and continue what I do. Then once it hits 100% battery, I would then unplug it and rinse and repeat. I did this with an old laptop at first but then I believe I just left it plugged in all the time. I remember people said don't do it that way as it makes your battery get bad even faster... is that true? That laptop no longer works anymore but that wasn't the reason it broke though.



With my dell xps 15 9550, my laptop I always have it plugged in via ac charger. Now I recall someone mentioned if you want to make your laptop battery life last longer... it had something to do with making it only charge up to 80 or 90% right? Like when it charges, make it never go higher than 80 or 90%? Also something like make sure it stars recharging once it hits 35% or something like that? That way the battery will have a longer life span?



If so, how do I do this? And do most of you do this? Im talking about those that use it as a desktop replacement basically.
Is there proof that doing this... as oppose to just having it plugged in all day 100% for 12+ hours will make the battery life span last longer? Like people here done it and said yea... me doing that made it last another 6 months or so? My first laptop battery the 56wh that came with this laptop years ago... lasted almost 1.5 years and by then, the battery was no good... didn't even had a minute anymore. My last battery that I used for 2.5 years... it pretty much had like 5 minutes only left after 2 years. So because of how I use the battery, as a desktop replacement and charged all the time, seems like i need to get a replacement every 1.5 years or so.



So does making it max 80% or 90% mean it might make my battery go 2 years or so or even? I noticed in my battery report, after 1 year or so with a battery, it gets worn real quick the way I use it. Now i know I could use it without a battery and just plugged in... but issue is when this happens, and say I have a power outage... well that would ... though I would connect my laptop to a UPS so my laptop doesn't immediately turn off. Buf if i run out of battery with my UPS... i mean I do have a powerbank. But I also rather have my laptop battery inside ... and wouldn't feel good having to open it up just to put in the battery.