Yeah. RC LVC doesn’t really translate to esk8. The equivalent esk8 usage would be going uphill 30 degrees full blast and emptying the battery in 20 minutes. In those circumstances, 3.5v might well mean you still have 50% battery left due to voltage sag.
But for the most common esk8 usage which is very start/stop in terms of amp usage, 3.5v most likely means that you have used all your capacity and are damaging your cells.