Why Cummins trucks need the capacity

The 6.7L uses a grid heater rather than glow plugs, and it pulls hundreds of amps on a cold start. That is why these trucks run dual batteries from the factory. The factory alternator is sized for that load and little else, so a plow, an inverter, auxiliary lighting or an audio system eats the remaining headroom fast.

Mechman builds direct-fit high output alternators for the 6.7L from 240 amps up to 400 amps. Billet housings are available in a range of anodized finishes for trucks where the engine bay is part of the build.

2007-2010 vs 2011-2022

Both generations are covered here, but check your model year against the individual product listing before ordering. Bracket and plug details changed across the run.

Choosing a battery

These trucks run dual Group 65 or Group 94R batteries depending on year. Replace both at once and match them — pairing a new battery with a tired one pulls the new one down.

AGM tolerates the deep cycling of auxiliary loads far better than a standard flooded starting battery, and it handles the vibration of a diesel better too.

Don't skip the wiring

Dual batteries mean longer runs and more connections, each dropping voltage. Upgrading the main cable matters more on a diesel than a gas truck. See our Big 3 wiring upgrade guide and Big 3 kits.

Browse all Mechman high output alternators, batteries, or cable and wire.