https://www.gobilda.com/12v-nimh-nested-battery-3000mah-mh-fc-xt30-connector/

The nested form-factor of this 12V battery allows it to be tucked away in an 1120 Series U-Channel to protect it  from the moving pieces of your chassis. The XT30 connector is an easy-to-use, indexed style connector that provides a reliable and dummy-proof connection to the electronics of your robot.