But here is the secret the manufacturers don't want you to know:
Download your chosen ROM zip file and the corresponding GApps (Google Apps) package. Transfer these files to an external microSD card inserted into your tablet. Step 2: Boot into TWRP Recovery custom rom for samsung galaxy tab 3 sm-t211
Your battery is likely old (10+ years). However, flash a "Trim" script via TWRP or calibrate the battery by draining it to 0% and charging to 100% while powered off. But here is the secret the manufacturers don't
: Often cited as the best performance-focused option, SEAL (Speedy Extraordinary Appealing and Light) is highly optimized to run faster than the stock firmware. custom rom for samsung galaxy tab 3 sm-t211