logsplitter EV conversion

It's a massive over-simplification, but think of hydraulics like a lever or a pulley. The hydraulic pump compounds the force available from the engine. Going from 5.5hp to 1.5 will reduce not only the speed the ram would move, but also the force available.

Yes, technically a lower power motor will make the pressure and the ram will just move super slow - in reality the breaker will be tripping every time things get tough and the motor will stall out unless geared way down, and now the ram is moving even slower yet. In effect, the pump and motor must be sized to match one another to some reasonable degree and going from 5.5 to 1.5 is not close enough.

There are electric wood splitters out there. They tend to run slower, but work great for when you want to split a few peices but don't need to do it for 2hrs or in a remote location.
If I were dead-set on doing a DIY type deal, I think a 220v motor out of an old clothes dryer or air compressor would be where I'd look. Driving the pump off an elec motor, I would also look at running a belt rather than direct-drive with the flex coupler. That way you can vary the ratios a bit to see what works best and limit the current (amps) being drawn by the motor.
If you can't run a 220v motor for the project, then I wouldn't even bother. There's just not much juice available to do 'real' work with 115v outlets.

My wife hates loud noises, so I run the splitter, and she runs the axe.