Combiner Identification

• A battery combiner resembles a small car battery. However, it has outside connections for two incoming batteries. Two red, or power, leads attach to separate connections on the combiner, along with a ground connection for both batteries.
  
  

Functioning

• The combiner allows two batteries to charge simultaneously off of a vehicle's alternator. The combiner's circuitry is a relay system, allowing the batteries to function separately once a charging session terminates. The combiner does not require a voltage drop, or power source, so both batteries charge to their full capacity.
  
  

Combiner Advantages

• Two fully-charged batteries aid initial boat ignition, preventing a costly tow if one or both batteries are undercharged or dead. Recreational vehicles can remain idle, like parking at a boat dock or camping in the forest, and still have functional auxiliary power for running lights and appliances. Extra power is especially helpful on cold morning start-ups, providing an extra boost for a successful ignition for both land and water vehicles.
  
  

Combiner Choices

• A combiner's amperage, or current, rating must closely match with the vehicle's alternator current output. Verify that the combiner supports up to the same amperage quantity as the alternator. For example, if an alternator rates at 100 amps, purchase a combiner supporting 100 amps. However, the indirect combiner connection to the alternator allows a user to purchase a lower amperage rating, such as 85 amps matched to a 100 amp alternator. The combiner has an electronic thermal overload sensor that shuts the mechanism off if it becomes too hot.
  
  

Combiner Considerations

• The two batteries attached to the combiner should be similar in voltage levels and internal construction, such as two lead acid batteries. Mixing different batteries together impedes the charging process, requiring longer charge durations. In addition, a bad cell within one battery affects the entire connected battery group. The battery group will sense a load during charging, lowering the final charge of all the batteries.
  
  

Combiner Placement

• Verify that the purchased combiner is waterproof if the final installation area is near water, like on a boat. Many models have extreme temperature endurance levels, withstanding temperatures as high as 175 degrees Fahrenheit.