Carrying a Spare Battery on Magnum Metro

[Fred]

I wanted to carry a spare battery (for long trips) in my saddlebag, but the spare battery I have is not the REENTION DORADO-PLUS case battery, that is on the bike. My thought was to tap into the connection between the controller and existing battery and also install a DPST switch to enable one or the other. Because the REENTON battery/case is so integrated to the frame and connection to the controller seems to be buried inside the frame, I'm just trying to figure out how and where would be the best place to make this connection. Any ideas or has anyone done something similar?

 

[jc-ct]

The connection is behind the top piece of the battery holder. You need to remove 3 small screws (one removes a plastic cover that exposes another screw) to remove it from the down tube. The hole in the down tube for the display and headlight wires coming down is right on the other side.