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Author Topic:   Adding 3rd Battery
Sschmitzs posted 11-09-2007 08:11 PM ET (US)   Profile for Sschmitzs   Send Email to Sschmitzs  
Guys I'm new to this website and thought I'd seek advice on the electrical project on my 26' cabin cruiser that I'm planning.

Here's the situation: I have a two battery system that is currently in parallel w/ a factory installed 1-2-off-both switch.

I installed a windlass and connected to the positive terminal on one of the existing batteries. I've found that I have drained the power down overnight after anchoring up, running the stereo, refrig, etc. Most of the time I remember to keep the switch on 1 or 2 and keep one battery in reserve for engine cranking in the morning.

What I want to do is install 3rd battery which powers the windlass, stays fully charged, and can be used to parallel the existing two battery system at my discretion. This way if I forget and leave the battery switch in the "both" position and draw both down then in the morning I can manually flip a switch and have 3rd battery back-up power to crank the engine.

Any good advice on: 1. Battery Selection 2. ACR 3. Switch 4. Wiring Diagram

I've looked at the website, studied the info at WestMarine but am still a bit confused on how to rig this up.

Steve- Edwards, CO

jimh posted 11-09-2007 11:34 PM ET (US)     Profile for jimh  Send Email to jimh     
I would avoid complicated switching arrangements. Install a third battery as a HOUSE battery. Run the windlass from this battery, as well as your house lighting and electrical loads. Get an automatic combiner relay (ACR) --also called a voltage sensitive relay (VSR)--and install it so that it routes charging current to the third battery.

The more complicated the electrical switching arrangement, the harder it is to keep track of how to operate it. If you just add a HOUSE battery and an ACR, you will have a relatively simple system, and it should be no harder to operate than what you have now.

glen e posted 11-10-2007 05:37 AM ET (US)     Profile for glen e  Send Email to glen e     
A very simple way to execute Jim's post above:

Sschmitzs posted 11-10-2007 03:11 PM ET (US)     Profile for Sschmitzs  Send Email to Sschmitzs     
Thanks for the input!!!!Steve

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