MKR has a connector for LIPO, So you can connect LB-041 & LBB-041 to it.
But, You need to modify the LB-041 Cable (Robot Cable-2P for Battery Box (150mm)) to cross.
Swap polarities (crossing) of one connector as below image.
If you do not make this modify, your MKR will heat up. There is a risk of failure.