How do I hook my alternator up to an extra battery?

[McIntoshUSA]

My boat has 3 house batteries and one starting battery. They will all charge by the engine/alternator or my guest battery chargers. I have a trolling motor for my dinghy. I successfully hooked one of my 2 guest dual battery chargers to it so I can charge it with 110v. (this way it is not connected to any of the existing banks.)

I would like to hook this extra battery up the engine/alternator so I can keep it charged when not at the dock. Do I just run a charging wire from the alternator to the battery? It is not located near the other batteries. My other batteries have a small black box (ETA) that the alternator charging wire goes through before it connects to the house battery bank. I am guessing it is a fuse or some kind of charging regulator? (see attached photo). Do I need one of these on this extra battery? I do not know what amp my alternator is but it seems to be fine charging the existing 4 batteries. 12v system.

I am a little confused because my alternator charging wire exits this ETA box and goes to the house battery bank only. The house bank and starting battery is connected by the negative terminal. Its strange to me that their is not a hot wire to the starting battery to charge it but it does work?

 

[Maine Sail]

I am gussing your three house batteries are in parallel thus one house bank and one starting bank?

Leave the alt on the house bank and use an ACR, Echo type charger or the BOTH position on the battery switch to charge the start battery. DO NOT add a second wire from the alt to the start battery.....

P.S. Don't know what that ETA breaker is doing but it should not be in the path of the alternator. If fusing the alternator output wire at the battery bank a fuse should be used such as an ANL, Class T or MRBF....

 

[Stu Jackson]

End your confusion by drawing a wiring diagram.

These might help:

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

 

[McIntoshUSA]

Thanks, I was reading about the ACR. It sounds like that is the way to go. Do yo have any idea what this ETA box is?

Thanks for the help.

 

[weinie]

Thanks, I was reading about the ACR. It sounds like that is the way to go. Do yo have any idea what this ATA box is?

Thanks for the help.

google shows it is some kind of fuse.