97 Speedster dual battery & isolator wiring

[Roadtrippin1378]

Good day to all, I just got a new to me 97 Speedster twin 717 Rotax and want to install a second battery with a NOCO 90amp isolator for my stereo and amplifier.

The isolator has a bat1, bat2, alt, and ext connections.

The alt or alternator connection is where I'm stumped, I need to connect the current coming from the stators to this "alt" connection so the isolator can charge the appropriate batteries when needed.

Any advice?

 

[Roadtrippin1378]

The wires from the stators go into the electrical box to the rectifiers, there's a red wire from each rectifier to the main board. Do I disconnect these red wires from the main board and connect them to the alt connection on the isolator?