Disconnect car battery with receiver
This seems like a waste of time and effort and probably introduces a reliability safety risk.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. General overview schematic of automotive power distribution.

The starter solenoid, ignition circuits (spark plugs, etc.) and auxiliaries (lights, indicators, interior fan, etc.) are already controlled by the ignition keyswitch so there is no need for additional isolation. The always on power feeds things like the door lights and radio (which may need a password on power-up) and these are really the only leakage paths that you need to be worried about.


  All I could find were things that you manually use at the battery to disconnect the negative terminal. 


Isolating the battery negative is the recommended practice for maintenance because it eliminates the chassis return path. Consider what happens if you use a spanner to disconnect the positive terminal while chassis is still connected to negative: if the spanner touches any chassis metalwork while undoing the terminal a short-circuit will occur. That can't happen while disconnecting the negative terminal and once done it can't happen with the positive terminal. 

If you were to proceed with your scheme you would only need to cut the auxiliaries positive feed.


  The battery is 12 volts and outputs up to 810 amps.


There's the problem. You need a huge solenoid and you've got to keep it on all the time so it will run hot. You've also got to be very confident that it won't fail while running.

I suspect you are trying to solve an imaginary problem and can't think why you would want a solution that uses a remote control which introduces another level of complexity and potential random failure.