MPIII 48v settings motors shudder/vibrate.

[Lazyrider]

I have been playing around with the USB programming for my dual MPIII bike.
When I first got the configuration they were set to 24v from the GM factory- so I changed them to 48v.

When I took it for a ride I thought I had broken something!
Changing the settings had caused both of the motors to shudder/vibrate(like a halls failure) when I did anything but push the throttle down very slowly.

At both 24v and 36v the motors run great.

WHY???

Is it something to do with two motors drawing more watts than the battery can deliver?(I have the factory 48v 10ah and a 20ah and it happens on both packs- can I plug both batteries in-parallel to make it easier on them or will they load into each other/ cause other issues)

Is there any disadvantage to settling with this issue and keeping the motors on 36v settings(less torque? lower max speed?) or is the setting pretty obsolete?

Any ideas or help is much appreciated.

[GM Canada]

From my understanding the controller setting for voltage is ONLY to protect your battery. All it does is set the low voltage cutoff for the controller and nothing else.

So at 24 and 36 volts it will work fine. When set at 48 volts your battery must either be hitting the low voltage cutoff on throttling or the low voltage cutoff for the controller is faulty.

Gary