Question Bad battery life *HP 840 g1)

Jul 5, 2020
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Hello!
I have an notebook elitebook 840 g1 from HP. I bought it used and ordered a new battery since the battery life are not great. but even with the new original battery it lasts mayb 2 or 2 and a half hours. (simple work, office or web browsing)

the 8750m amd gpu is disabled.
I am always on battery saving mode.
the power plan is also on battery saving.
the cpu boost on battery is disabled. (BIOS)
keyboard lights are disabled.
always low to medium brightness.
I monitor the cpu utilization. It's never high.

what the crap is the problem?
thanks!