Macbook Pro shuts down abruptly at increasingly high battery levels with no crash report after

After updating to Big Sur about 2 weeks ago, my macbook pro's (retina, early 2015) battery capacity greatly decreased. At first the problem was the battery would be drained in as fast as 3 hours (usual browsing and document editing). I though this was acceptable because obviously with time and newer software updates, my laptop would just not work as efficiently as when it was new. But after a few days the shut-downs occured; first at about 20%, then 40%, and increasingly, and now I could not use it on battery anymore even at 100%. I have to plug it all the time to use it.

I have tried resetting SMC, NVRAM/PRAM and safe boot. Nothing changed.

Here is my battery Charge Information:

Fully Charged: Yes

Charging: No

Full Charge Capacity (mAh): 2816

State of Charge (%): 100

Health Information:

Cycle Count: 857

Condition: Service Recommended

I thought maybe the fact that my battery condition is "service recommended" is the cause but according to apple support's article on batteries I could still supposedly "safely continue to use [my] Mac" while on such battery condition. The article also says I "should take it to an Apple Store or Apple-authorized service provider to get your battery evaluated" but the nearest service center is 5 hours away and I am a student struggling with my finals so I can't do so as of now.

Last thing is, after i turn it on again, there are no crash reports so i can't really identify or solve my problem.

There is a similar thread to this (https://discussions.apple.com/thread/1620583) but the dates are all in 2008, and I've tried their suggestions to no avail.