How to connect one batt for accessories and one for starting?

[LadyAnya]

Hello, I am new to the boating world and I am interested in knowing how to connect one batt just for starting and the other for running accessories. I have an 88 sunrunner, I am not sure how the wiring is now, however I prefer to have one batt for starting and the other for accessories.

Thanks

 

[LadyAnya]

Re: How to connect one batt for accessories and one for starting?

any ideas

 

[NYBo]

Re: How to connect one batt for accessories and one for starting?

There are a couple of ways to do this.
1. Separate the engine and house circuits.

2. Install a battery switch. There are diagrams in this forum for wiring it, not to mention the instructions that come with the switch.

Option #2 is more versatile, and the preferred way to do the job. It allows you to choice which battery to use when starting and when just running the house load. With no additional components, you can also decide which battery gets charged by the alternator. You can also hook both batteries together in parallel through the switch, for either load or charging.

 

[LadyAnya]

Re: How to connect one batt for accessories and one for starting?

The battery switch does sound more versatile. So I just use the + and - of the battery that I will use for the accessories only right?

 

[NYBo]

Re: How to connect one batt for accessories and one for starting?

Both batteries connect to the switch. You use the switch to route power from whichever battery to the existing electrical system. The only exception would be power to an automatic bilge pump; you don't want to accidentally shut it off when leaving the boat in the water, especially unattended. You would hook the bilge pump directly to one of the batteries. Here is a diagram, as provided by Silvertip:

Here is another diagram:

 

[malone1956]

Re: How to connect one batt for accessories and one for starting?

Another option is to connect a battery isolator on the accessory battery. This allows the battery to be charged by the motor while the engine is running, but prevents the main battery from being drawn down while stopped. These are really popular in truck campers for the same reason. You want the battery to be charged while driving, but don't want to pull from both batteries while in the camper.