Batteries tend to seek the same level when combined and a completely dead auxiliary battery circuit could drag your cranking battery down too low to crank your engine or keep it running. This feature also prevents combining your cranking battery with an auxiliary circuit that is shorted or otherwise faulty.

Your pickup’s electrical system includes expensive components that can be damaged when fed the wrong number of volts!

Auxiliary Battery Systems

The big advantage of a separate auxiliary battery system is the ability to wire additional batteries in parallel for a virtually unlimited supply of accessory power.

If you need to mount more than two big deep-cycle batteries, however, you might check with your dealership’s service manager or a local electrical service shop to ensure you have enough alternator to handle the load.

A single extra battery may fit under your hood, but multiple batteries will probably have to be mounted in the truck’s bed or under the body.

Installing them in securely anchored marine battery boxes contains any electrolyte spillage, provides safe ventilation and keeps an insulating layer of plastic between the batteries’ posts and your truck’s metal body.

Battery Types

Batteries come in three types suitable for work truck use. The first and oldest design is the flooded-cell, full-maintenance type.

Many AGM batteries, like this Deka Intimidator model, have both threaded and clamp-on posts, making it easier to wire up more accessory power cables with either type of terminal connector.

These have removable caps that allow you to check the electrolyte level in each cell and replenish it as necessary by adding distilled water. This antiquated design remains popular because it continues to provide more amp capacity per pound and per dollar than other lead-acid battery types.

The chief downside to these flooded, full-maintenance models is that they must be checked and serviced regularly, including cleaning their tops and posts as necessary to prevent a buildup of crud heavy enough to leak voltage between their positive and negative posts.

Exide’s rugged Megacycle AGM batteries are backed up by a nationwide dealer network, making them easy to buy and service.

Flooded, maintenance-free batteries also have flooded cells with vented caps, but the caps are not removable. These batteries are designed to provide a lifetime of normal use without needing additional water.