Optimizing 6-Cell 97WHr battery in XPS 15 9570 when using a 130w docking station

Thanks so much, @jphughan!

Your answer is perfect. I got the 50-80% charging idea from one of your replies in a different post, but I wanted to make sure the watts of the docking station wouldn't be a problem. I'll double-check the watts of the docking station and whether or not my laptops battery is even going down during evening use, because I assumed it was since I got the BIOS warning when I power on the laptop with docking station plugged in.

@NickPhD  setting your battery's minimum and maximum charge to 50% and 80% is a great step toward maximizing your battery's longevity, as long as you can live with the possible inconvenience that if you ever need to disconnect from a power source unexpectedly, you could potentially only have a 50% charge.  I'm surprised your XPS 15 is draining its battery even though the dock power source is undersized for that system.  Typically it just throttles performance, but if you're running heavy workloads even the throttling might not be enough.

In any case, if your system is draining is battery a bit even while connected to a power source, then that's not any worse than using the laptop on battery power in a normal situation -- in fact it's better since the drain isn't as fast as it would be in that case -- but the even better option would be to eliminate the battery usage entirely.  So to that end, if reasonably convenient I would recommend keeping the system's own 130W power adapter directly connected as often as you can.  There's no problem at all having that connected even while connected to a dock that can supply power; the XPS 15 will use the directly attached power source if it provides more wattage.  At that point, since you've got that 50-80% configuration in place, your battery will spend most of its time completely idle, i.e. neither being charged, nor being kept topped up, nor being actively discharged by usage.  That's the best setup from a longevity standpoint.  And capping the battery charge to 80% helps even more.  Tesla vehicles default to charging only to 80% unless you specifically choose a Max Range charge, which has to be selected each time you want it (i.e. you can't make that the default) and as of a recent iOS update, iPhones plugged in to charge overnight will spend most of the night with their battery charged only up to 80%, and will only charge all the way to 100% shortly before they expect you to disconnect it from overnight charging, based which they determine based on your calendar and past behavior.

Lastly, if you can get your hands on a Dell 180W power supply, you could use that with your WD15 in order to get it to supply adequate power to your XPS 15.  They can be bought separately from docking stations, and any official Dell 180W power supply will work, because Dell has standardized their power supply voltage going back at least to 2003, and since then their 180W power supplies have only ever had one style of barrel connector, so like I said, any Dell 180W power supply you can find would do the job.

@NickPhD  Glad I'm able to help!   I suspect you might find that your battery isn't depleting through the night, at least not beyond a small amount of "self-discharge" that would be normal in a 50-80% configuration.  The BIOS warning about an undersized power source doesn't mean that your system is guaranteed to keep drawing from the battery while plugged in; it just means that you might see slower battery charging and/or reduced performance.  However, even if you find that your battery drain isn't anything beyond normal self-discharge, it would still be worth keeping your system's AC adapter connected if it's not too inconvenient, because your system will perform better when you give it the full 130W it's designed to have available.  A WD15 powered by a 130W adapter can only pass 90W through to the attached system because the WD15 reserves some of that capacity to run its own internal electronics and provide power to any USB devices you might plug into it.  Good luck!