Dell XPS 13 9350 Signature Edition battery life issues

I'm assuming windows 10 is on the computer

I suspect battery life cycle is coming to a end. Please, keep in mind, battery life span is how often a battery can be recharged before the charge capacity starts to reduce. Normal characteristic of a rechargeable battery is that the charge capacity reduces gradually with each discharge-charge cycle. Typically, you will notice reduced battery life after 18–24 months. If you are a power user, you may notice reduced battery life sooner than 18 months

Now, you could run Dell ePSA hardware diagnostic test to check Battery Health or uninstall /reinstall Microsoft ACPI Battery driver in device manager to make sure the battery isn't failing or a faulty hardware that causing the battery problem - see link below):

How to Troubleshoot Dell Laptop Battery Issues

https://www.dell.com/support/article/en-us/sln292953/how-to-troubleshoot-dell-laptop-battery-issues?lang=en

You can even generate a battery report by following steps below.

- Press and hold Windows logo and press R key.

- In the Run dialog box, type cmd and press Enter key.

- In Command Prompt window, type powercfg /batteryreport and press Enter. (note the space between powerfg and /batteryreport).

- Open File Explorer and browse to C:\Users\Your_Username\.

- Double-click battery-report.html to open the report in the browser.

Design Capacity - is the actual capacity of the battery it was designed for

Full Charge Capacity - is the consumption of the battery's capacity. Over the period of time or usage, Full Charge Capacity get reduced as the battery ages which results in lesser hours of usage between charges.

If indeed the battery is failing, check Walmart and Parts People com for battery prices in link below:

Genuine Dell XPS 13 9350 56Wh 4-Cell Battery 90V7W

https://www.walmart.com/ip/New-Genuine-Dell-XPS-13-9350-56Wh-4-Cell-Battery-90V7W/500194717?wmlspartner=wmtlabs&adid=22222222222258500797&wmlspartner=wmtlabs&wl0=e&wl1=o&wl2=c&wl3=74560721794462&wl4=pla-4578160283864543:aud-807615483&wl5=&wl6=&wl7=&%20wl10=Walmart&wl12=500194717_10000008424&wl14=Dell%20XPS%2013%209350%20battery%20parts%20poeople&veh=sem

Dell XPS XPS 13 (9350) Battery | Dell XPS XPS 13 (9350 ...

https://www.parts-people.com/index.php?action=category&id=143&subid=559&refine=battery

Note: Parts People sell quality genuine Dell parts. Most people will suggest that website for Dell parts. 

Thank you so much for your response! I found this on the Parts People website, but also found these on the Amazon and iFixit wesbites. The alternatives are cheaper, but would you say that they are known to be less reliable?

Also I ran the design capacity of my computer - it's now around 3000 mWh compared to its original design of 55k mWh and can run for around 21 minutes. I read about other people with this issue who reported 'swelling'. How do I check for this? As of now I have not noticed any issues with the touchpad that they reported. 

You indeed need a new battery.

The seller (SANISI) on Amazon has mix reviews, some people say Battery function well and others complained about battery isn't detected in BIOS and doesn't work at all - see link below):

DELL 90V7W Notebook Battery / Amazon Reviews ON Seller:

https://www.amazon.com/SANISI-Notebook-Battery-Compatible-Quality/product-reviews/B07DFRQG1J/ref=cm_cr_dp_d_show_all_btm?ie=UTF8&reviewerType=all_reviews

Ifixit does looks enticing( tools set including with battery purchase) but I am not familiar with this website. Keep in mind, genuine Dell batteries have these microchips to help people detect counterfeit batteries. Some third parties have taken a microchip from a dead genuine battery and have inserted it into the counterfeit battery. 

Now, i am not saying batteries from Amazon, ifixit or another third party won't work, all I'm saying you're taking a chance with them. I do see, Amazon and the seller has warranty on the battery, so does ifixit.

Service Manual / Removing Battery just in case you want to view it.

Support for XPS 13 9350 | Documentation | Dell US

https://www.dell.com/support/home/us/en/19/product-support/product/xps-13-9350-laptop/docs

Good luck with your search for a new battery.