How do I connect if I have dual motors?

A standard marine battery of 75 Ah has a starting current of just over 600 A. The battery is capable of starting both engines, provided you wait about one minute after starting the first engine, as by then the battery is ready to start the next engine without any problems.

Use the space for an extra consumer battery instead. If 600 A is not enough, choose a pure starter battery with a higher starting current.

In our wiring diagram proposal alongside, we have utilized the boat’s generator capacity to the fullest.

Engines consume well under 1 Ah per start. The charging requirement of the starter battery is therefore very small. The surplus charging current from the generator to the starter battery will instead be passed on to the consumer battery bank and top up the charge there.

However, the starter motor requires high power, meaning high current; a 200 hp diesel draws approximately 600 A. This high current causes the voltage in the starter battery to drop so much that the starter battery draws the largest share of the charging current of all batteries immediately after engine start.