Help an idiot

**muchy_** · 14-09-02, 17:15

My boat has just one battery bank that serves domestic and engine start. Now, thinking that this is a disaster waiting to happen (wife and kids, none of whom realise that turning lights off is important) I decided to buy a split charge diode thingy and another battery. Now, can anyone explain in laymans terms (thick as s**t) where the cabley wirey thingys go and what size of wire is needed etc......
The setup is single alternator with two battery banks. Three terminals on the diode. Center one being common.

**halcyon** · 14-09-02, 18:14

Simply the output from the alternator goes to the common, the other two outputs go to pos on the two battery banks, use 10 mm cable unless you have very long cable runs or large alternator.
Down side, unless you have a battery sensed alternator, is you now need to buy a smart alternator reg to compensate for the volt drop in the blocking diodes. If you run with blocking diodes only, you will loose around 30 / 40 % of battery capacity due to volt drop in charging circuit.
A smart relay would have saved you a lot of cable work and the need for a smart regulator.

Brian

**muchy_** · 14-09-02, 21:03

I also have a sterling alternator controller thingy to put on but that comes with full instructions so is not a problem but the diode has no instructions.

OK, so the feed from the alternator goes to the middle terminal and each of the other terminals go to the pos of each battery, but where do the negs go? Can I just link the two negs together? And how do I determine which battery will be the engine start? Do I just take the neg from the starter to the battery that I want to be the starter battery and then the domestic pos and neg to the other battery?

(told you I was an idiot)