If you are kind enough to respond to this question please note that when it comes to understanding the electrical systems on our boat my knowledge is VERY basic.

Whenever I leave the boat I always disconnect the batteries (remove the 2 battery "keys"). On a recent visit however I forgot and when I was next on the boat the batteries were dead having drained of all charge. All switches etc were turned off. I don't have a solar panel to charge the batteries when I am not on board and the motor isn't running.

This suggests to me that there must be something that is drawing power even though everything is turned off at the switches. So my first question is this an accurate assumption or do batteries when left connected just drain power even if there is nothing drawing that power?

I have seen / read on here from time to time talk of people checking different systems or electrical components to pinpoint what / where current is being used. Firstly, how do you do this, what are the steps? Secondly, is it likely that this process would identify where the power from the batteries is being lost?

Thanks in advance for your help and assistance.