House Battery Charging Issue

[denpooch]

Hey Folks I hope you can help with this one.
I have discovered that my house battery is not charging while underway. I checked and the alternators are working. The starting batteries are charging but for some reason the charge is not making its way to the house. The house battery does in fact charge when plugged in dockside electric. All wires seem tight.
One question is how is the battery wired so that only the house battery will discharge for d/c demand while the starting batteries do not discharge, yet is able to accept alternator charging.
I there some solenoid or switch that can be defective?
Any thoughts and insight are much appreciated. Thanks.

[g36]

What boat model? There's probably a selector switch somewhere maybe under a stair like my 405 or ? . Battery charger has multiple legs so different batteries are charged when plugged in. Depending on battery selector switch alternators could be working but selector swich has house cutoff from charge. Never now how a previous owner may have changed stuff around either.

[darrenlife]

You may also have a battery isolator. Both alternators are likely going to the input side of your isolator and should be 3 output legs, one to each starting battery and one to your house?

[bud37]

To answer we will need a little info.....I assume your disconnect for the house battery is on , do you only have one house battery ?, how have you determined it is not charging from the engines ? Perhaps the battery is just dead or shorted, when on shore power your charger is on therefore 12 volt DC is available to the house loads, the same underway if you run the genny or the engines are running.
The tell would be to disconnect your shore power, gen off then try DC house loads, put multimeter on the house battery then start an engine and see what registers, or disconnect the leads on the house battery and have it load tested.
Also like g36 states, ya never know what has happened before you..plus consider what darrenlife says...good luck with it...

[denpooch]

The boat is a 2005 Mariner 36.
I let the battery 'run down' yesterday and put a meter on the battery and started the engines. No movement. I do know the alternators are working from dash voltmeters. The battery is brand new this season and has been tested.
I am gonna check all circuit breakers and look for an isolator.
Thanks folks, I will keep you posted on progress.

[Midnightsun]

You must have some battery switches. Are they simply the on/off type?

[denpooch]

I FOUND THE PROBLEM!
The battery has 3 red cables connected to positive terminal of the house battery. The largest seems to feed the system. Second seems to be the input from onboard charger. The last is inbound from the isolator. This cable went from the terminal to a breaker and that breaker needed to be reset.
I checked voltage before and after starting the engine. She is charging!
Thanks for your advice.

[Midnightsun]

Gotta love an easy fix and happy ending. Not often it cost zero boat dollars.