MacBook Pro going in low battery deep sleep when opening demanding app

So here is my issue. (While disconnected from it’s charger)

I recently bought a used MacBook Pro 15 Early 2013. Battery is not at it’s best. 5418 mAh out of 8460 mAh. The MacBook does great when doing small applications (safari, numbers, spotify). Battery works okay in 100% to 60%) range.

However, as soon as I open up demanding applications such as Lightroom, Photoshop, Minecraft (or just any game to be honest) the MacBook Pro just goes into Deep Sleep mode after 15-20 seconds. As soon as I try to open it, there’s the “Charge me with the red battery icon”. So can’t turn it on unless I put the charger on the Mac.

Turning it back on doesn’t show like 1% battery, it just shows just about to where it was (i.e, being at 75% while shutting down, plugging it in and opening it will be still at 70-80%).

I noticed also while opening Lightroom once, the battery voltage dropped to 10.2V, which is lower than the constant 10.8V that it’s supposed to get?

Seems like it’s the original battery, as it turns out it has 719 cycles and 8 years.

So is this only a battery related issue? Thanks in advance,

William.

[EDIT] First screenshot is after replying to Dan’s comment.

Second screenshot is right after replying to his comment.

So there is around 5 mins between each screenshot.