You may remember that boat batteries can have three different positions: services, engine or both of them. A configuration which still appears in thousands of boats but that is disappearing on modern ones.
Today, in fact, producers avoid a parallel connection between service and engine batteries in order to prevent that a forgetfulness, while services are working, could provoke the engine battery exhaustion and the consequent no-starting.
Anyway, it could happen that engine battery looses its charge and starting isn’t possible.
On an old boat, we could exploit the amps of the service batteries. But, if we have a modern boat, where this possibility doesn’t exist, what can we do?
We can try to create an electric bridge, as showed in the video above, in order to exploit service charge in favour of engine battery.
To do that, it’s sufficient to find the battery master switch pins and link them with a wrench in order to create a parallel connection. This way, if the engine battery is out of power, it will benefit from the amps of the service batteries.
The video refers to a medium-sized sailing boat, the new Dufour 412 Grand Large. The “trick” is not valid in any kind of boat, so be careful ( a knowledge of the specific electric system is required) and ask for an expert advice.