Alternator wiring to Sterling A to B charger .. help please

[Albert Ross]

I've already explained in post #2 which are the two connections you need to know. The others aren't really important for you, but item 2 is B-, item 3 is a cable clip, item 4 is a negative feed, and item 5 is the tachometer output.

You need to follow the Sterling instructions very carefully, although they are rather badly written. Once you've wired the A-to-B charger, you must check that the alternator is generating and, if it isn't you'll need to add an ignition feed wire. This goes from terminal 17 on the ignition key switch to the "ignition feed" terminal in the A-to-B charger (shown as 4 on Sterling's diagram). If wiring to the key switch is complicated, you can alternatively wire it to the starter relay (the white wire on the starter relay).

Edit: Looking at your boat wiring diagram, it seems you have a relay to charge the domestic batteries automatically when the engine's running, and disconnect them when the engine's off. This is item 73 on your diagram. You'll need to disconnect this, and connect the domestic output of the A-to-B charger direct to the domestic batteries (using appropriately heavy cable, as specified in Sterling's instructions).

Perfect .. thanks .. exactly what I wanted to know.

 

[William_H]

Sorry William you need to read the installation and instruction manual.

But in brief the input to the AtoB chrger connects to the alternator output. And the outputs from it connect to the two batteries.

It fully loads the alternator and provides multistage charging of the domestic battery and standard charging of the engine battery. Although it does so by switching between them.

Thanks Vic I am getting my education slowly on this forum. I can see that really loading down the alternator witha connection just to the engine battery would tend to discharge the engine battery. So taking output from the alternator (isolating from the engine battery) means that both batteries can be correctly charged. Or at least the engine battery won't be pulled down. This is the advantage over the single output type someone mentioned. Is this a problem. I imagine that as the domnestic battery voltage rises the load on the A2B would lessen so allowing the alternator to regulate to 14v so bringing the engine battery back up. But for a short engine run it could take a lot of charge out of the engine battery without that isolation.
But of course the single output type woud be easier to install. Yes Charles you are right about being seduced by advertising blurb. Only in terms of understanding though. For me 5w of solar is more than I need. olewill