The Combiner 100 is suitable for engines with alternator ouputs up to 100 amps. This covers most outboard engines. If you have a higher output, you should use the Combiner 160.


Traditional battery isolators require you to modify the electrical wiring in your outboard to get to the alternator output. This involves extra cables to the engine and often voids your warranty. Battery isolators also have a built in voltage drop so now your starting battery and your trolling battery no longer get a full charge.

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Just connect a COMBINER 100 between the starting battery and the trolling battery. Whenever the outboard engine is running, the combiner will share the charging output with the trolling battery. When the engine is off, the trolling battery is separated from the starting battery and will not accidentally discharge it. Trolling battery schematic


  1. Mount the Combiner 100 in a convenient location, typically within 2 feet of the starting battery. The Combiner 100 is waterproof - submersible - so it does not need to be under cover. It is an advantage, but not essential, that the LED indicators on the combiner are visible. A location out of direct sunlight will help visibility and keep it cooler.

  2. Connect one of the red leads to the positive terminal of your starting battery. Since the Combiner 100 works both directions, it doesn't matter which red lead you use.

    WARNING: Make sure the other red lead is not touching anything so it won't short out if the combiner turns on.

  3. Connect the other red lead to the positive terminal of your trolling battery. You will usually need to extend this lead if the trolling battery is mounted in the bow. Since you have to connect the negative terminals of both batteries together, it is often convenient to use a 10 gauge duplex cable for the extension. It is OK to cut off the existing terminal on this red lead but do not shorten it.

  4. Connect the negative terminals of both batteries together. This provides a return path for the charging current that is going to the trolling batery. As mentioned above, this could be the black wire of a duplex cable going between the batteries. The cable or connections to the trolling battery must be very well protected from damage, especially in a metal boat. You should rout the cable where it will not be damaged, or enclose it in a counduit for protection.

  5. Connect the black lead to the negative terminal of the starting battery. It is OK to shorten this lead.

  6. You don't need the green wire. Cut it off, leaving about 3 or 4 inches remaining in case you ever need to connect to it later. The end must not connect to or touch anything so crimp a cap over it, or wrap with insulation tape.

That's it, you're done. Now whenever the engine is running, the green light on the combiner will indicate when it has connected to the trolling battery to share the charge. Shortly after turning the engine off, the green light will go out indicating that the batteries are isolated so the trolling motor won't run down the starting battery. The ability of the alternator in the outboard engine to keep the trolling battery charged is dependent on the size of the alternator and how long the outboard engine is running in relation to how long the trolling motor is running.

The red light should never come on. If it does it indicates that the combiner 100 is being overloaded and has shut down to protect itself. It will reset and attempt to continue working after it cools but you should try to determine what has caused the problem.