It would be much easier to use a small toggle switch on the throttle signal supply to the controllers, rather than use a heavy duty switch on the battery feed.
A single
Mini DPDT ON-ON-ON Toggle switch would be a good choice, but you would also require a couple of 12K resistors connected between the +5V throttle supply and the throttle signal wires going to each controller to prevent throttle failure mode from being activated when either throttle is switched off.
The switch can easily be wired so that both motors operate together in the middle position, and front only or rear only at either end position of the switch.
If you would like to wire it up this way, let me know and I'll try and draw up a simple wiring diagram showing the required switch connections.
Another alternative would be to have a pair of On/Off switches, one on each controller's throttle signal lead to enable Front, Rear, Both or None, depending on the switched combinations. Each of these switches would still require a 12K resistor connected between the +5V throttle supply and the controller signal wire for the same reason mentioned above.
Switching the throttle signal would ensure that the regenerative braking would still work on both wheels, regardless of whether the throttle was turned on or off.
If you could get hold of enough matching plugs and sockets, you could make up a separate adaptor harness that could simply plug into one set of controls, and both of the motor harnesses, but crimping those tiny connector pins can be a very fiddly and time consuming job.
So long as you take care with all of the connections and ensure they are all correctly joined and insulated, then you should not have a problem with the warranty. However, if you wire it wrong and reverse the polarity or supply battery voltage to the 5V supply lead etc. then that would be a completely different matter.
Alan
