Battery combiner

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Battery combiner

Post by Expatriate » Sat Sep 29, 2018 6:05 pm

About ten days ago I decided it was time to start the engines and run them till they warmed up just because we should all do this once in a while. No problems, the were fine. Then it hit me: the battery switches on both engines were off. How did they start?

After some head scratching I realized that if the boat is plugged into the dock and the charger is on, or if the solar panels (my case) are charging, the battery combiner connects all the batteries to the charging source. Fine, but how did the engines start? Upon tracing the wires from the combiner, I found that they did not go directly to the battery. They went to the battery switch in the stateroom.

Still no problem. It is just convenient. However, the combiner wire was attached to the wrong side of the battery switch. It was attached to the starter side of the switch, not the battery side. With the engine switch off, and batteries combined, the engines basically started on the house batteries. Seems unlikely, but that combiner wire to the start battery is at least a 4 gauge wire. So it carried enough current to start the engines easily.

Now all this may seem a moot point, and it is except for something that happened a few months ago. I started the starboard engine and the starter would not disengage. Every time I pushed the stop button, the engine restarted. Finally, it stopped, but it burned up the starter. I replaced it with a great deal of labor.

In this instance, with a starter that will not disengage, the thing to do is turn off the juice to the starter. That would be the battery switch in the stateroom. At that time, this would have done no good because of the way the combiner wire was routed. If the batteries were combined, the starter would have just kept starting the engine. Which it did.

Another problem with this is that, if you turn off the engine battery switches for safety, they do not get charged when the combiner connects them all together because the wire is on the starter side of the switch not the battery side. In any case, it is a simple fix that took 15 minutes. Just remove the locker above the switch and move the combiner wire from one side of the switch to the other.

This is probably not the case with all PDQ 34's. A simple test is to turn off the engine switches, see if the batteries are combined, and turn on an engine switch. You do not even have to start it. If it has power to the start switch, you have this easily correctable problem.

Isn't wiring wonderful?


M/V 068 Expatriate

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Re: Battery combiner

Post by AMCarter3 » Sat Sep 29, 2018 7:25 pm

Very useful, Tim. Thanks. I'm going to add this to my winter maintenance list.
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98; twin 100 HP Yanmars
Home Port: Bellingham WA 98229
Member of San Juan Sailing & Yachting charter fleet: ... .php?id=35

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