How do I connect if I have dual motors?

A standard 75 Ah marine battery has a starting current of just over 600 A. The battery can start both engines if you wait just under a minute after starting the first engine, because 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, buy a starter battery with a higher starting current, such as Tudor Maxxima.

In our scheme proposal next door, we have fully utilised the boat’s generator capacity.

Engines use 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 go to the consumer bank and boost the charge there.

On the other hand, the starter motor requires high power, i.e. high current; a 200 hp diesel draws about 600 A. The high current causes the voltage in the starter battery to drop so much that the starter battery draws the most charging current of all batteries immediately after the engine is started.