How to Connect Multiple Deep Cycle Batteries

by G.K. Bayne

By connecting multiple deep cycle batteries, you can increase either the storage capacity or the voltage of any battery system. The most common connection is a parallel termination, in which the power is increased, but the voltage remains the same as each individual battery. In other words, a bank of parallel-connected 12-volt batteries will still provide 12 volts of power. A series connection, meanwhile, increases the voltage by each individually connected battery: four series-connected 12-volt batteries will provide 48 volts of power.

Lay the batteries next to each other, so that the long sides of the batteries are 1 or 2 inches apart. (Maintain this space between the plastic cases--the batteries will swell slightly during certain times of the year.)

Attach the battery post connectors to each top post on the deep cycle batteries. Use the 1/2-inch end wrench to tighten the clamp's bolt. Do not over tighten the bolt, but make it tight enough so the clamp cannot move on the battery post.

Make a parallel connection of the deep cycle batteries by connecting all the positive terminals together. Begin at one battery. Insert one cable into the top post connector's cable clamp. Tighten the cable clamp with the 7/16-inch end wrench. Run the cable to the next battery's positive terminal. Make the same connection at this battery, and so on, until all the positive terminals are connected together.

Repeat Step 3 for the batteries' negative terminals. The total voltage will remain the same as each battery's individual voltage: 12 volts. The storage capacity, however, will be multiplied by the number of connected batteries. In this example, a bank of four parallel-connected 500 amp-hour batteries equals 2000 amp-hours.

Make a series connection using the same batteries. Assume that all of the battery connectors are already attached to the top posts, but no cables are connecting the batteries.

Run a cable from the positive terminal on one battery to the negative terminal on the battery next to it.

Tighten the cables in the battery connector. Perform the same connection from that last battery's positive connector to the next battery's negative connection. Keep making this cable connection until all of the batteries are connected together from the positive post to the next negative post. In this type of connection, the voltage of the four batteries will total 48 volts. The overall storage charge is equal to each individual battery's capacity, or 500 amp-hours.

Items you will need

  • 4 deep cycle 12-volt batteries, 500 amp-hour capacity
  • 2 battery post connectors for each battery
  • 2 battery cables, 18 inches minimum length for each connection
  • 1/2-inch end wrench
  • 7/16-inch end wrench

Tip

  • Connecting multiple batteries creates a large storage bank of power. These storage banks can be used for marine trolling motors, back up home electrical systems and vehicle winching systems for recovery.

Warnings

  • When connecting or charging deep cycle batteries, in parallel or series connections, use only a single type of battery in the configuration. In other words, do mix a regular car battery with a deep cycle sealed gel cell. Mixing battery types in any storage bank will cause permanent damage to the batteries.
  • Locate batteries in a well ventilated area. When batteries are charging or discharging they will emit a flammable gas.
  • Keep all batteries away from open flames.