Connecting 3 AWG wires
I recommend the ISR-10 by NSI Industries or equal. They splice and are completely insulated. Pretty much foolproof. You can Google them and you will see what I mean.

http://www.nsiindustries.com/catalog/nsiproducts/polaris%E2%84%A2-mechanical-connectors/polaris%E2%84%A2-black-insulated-connectors/isr-1-0

This might get you there. You can probably buy them online or from a wholesaler or someone like grainger.