is this possible to undervolt these 2 hub motors ( HUB24E / Model: MW12B ) to 18 volt - pr even 14 through the GM controller ?
Yoma, as the MW12B is a brushless motor it should work happily with the Magic controller, but it would still require a 24V battery, as the low voltage cut-off would prevent the use of voltages lower than ~21V. It should be possible to run it on voltages as low as 18V
(with a suitable brushless controller that's designed for 18V use) but the speed and power would be significantly reduced.
The HUB24E however, is a brushed motor and therefore cannot work with the GM magic controller at any voltage, but if you can find an 18V brushed controller, it should also work, but again there would be a noticeable reduction in speed and power.
Please also note that this motor is equipped with an electrically operated brake release unit which requires a minimum of 18V to operate correctly. If you are considering using an 18V
SLA battery configuration, the recommended minimum discharge voltage is ~15.75V, but this might not be enough to operate the electrically operated brake release mechanism.
As the MW12B is a brushless motor, it should work with the Magic controller, but it would still require a 24V battery as the low voltage cut-off should prevent the use of voltages lower than ~21V.
Alan