Posted: Wed Mar 03, 2010 9:41pm

my 1991 narrow boat with it's 1.5 bmc engine has 3 x 110a cabin batteries and 1 starter battery, they are isolated via 1 master switch in the neutral side (ground).my question is this acceptable or would it be best isolating the live side of the battery banks seperately ? what ever your answer could you please explain why, Cheers, Alan

Posted: Thu Mar 04, 2010 8:23am

First of all I very much hope it is not in either the neutral or ground cable. Both those terms are related to a mains AC supply. I assume that you mean the negative and in marine use it should only have one negative connection to the hull rather than using the hull as the return conductor as you would on a vehicle. Now the question. If you switch in the negative it is possible to save the cost of one switch so its popular with the boat builders. However under certain, admittedly rare, conditions and with certain equipment switching in the negative could result in a cable burning so I would never do it. A fault could also make the hull go positive with the master switch off. This is not good in respect of potential corrosion. Also if you have switches in the positives you can work on one of the electrical systems whilst leaving the other working. Tony Brooks