3 batteries, 2 switches... Am I over thinking this?

TBarCYa

Senior Chief Petty Officer
Joined
Apr 13, 2005
Messages
781
Right now I have two batteries and a single 1/2/B/O switch that I'll call switch1. The common connects to both the engine and the "house" breaker so whatever the switch is on runs the whole boat. I normally start from the starting battery then switch to both to charge while running and then switch to the house battery when the engine is not running. But I have forgotten to switch to the house when anchored and it's very inconvenient when fishing.

What I'm considering is having the common for switch1 connect only to the engine and installing a second 1/2/B/O switch (and a second deep cycle house battery) on the house side with it's common connected to the house breaker AND the #2 position on switch1. The goal of course is to be able to run the house (lights, stereo, GPS, fishfinder, VHF radios, pumps, etc) without ever worrying about draining the starting battery. In this configuration, the only way the house could drain the start battery is if switch1 is in the BOTH position which I would never use unless I had run both house batteries down and wasn't headed to the marina to plug in to shore power.

So assuming a single day on the boat I would be able to turn both switches from OFF to 1, start the engine and run to wherever I'm going to anchor or fish then spend the entire day with the electronics running and still be able to start the boat to get back to the slip and turn both switches OFF and let the charger do it's thing.

So that's what's on my mind today. Am I over thinking this? I'm trying to make it as fool proof as possible and this seems to do it with minimal expense with only having to purchase a switch and the battery cables to connect the house batteries to the new switch.

Thanks
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,300
you already have a simple system

battery 1 is your start battery
battery 2 is your pair of house batteries

you are over-thinking it

I generally charge each battery at the beginning of the season with the cables disconnected

then battery 1 for starting, allow motor to warm up (dealing with lines, etc.)
switch to all for motoring to your anchoring spot
shut off motor, then switch to battery 2 for house loads.

in your case, you will be using shore power to keep your house batteries topped off
so run the motor on battery 1
run the house loads on battery 2

you can use ACR's to charge if you want to try to make it a bit more fool proof.

AllDodge has a nice sketch of a system using ACR's and a single switch.
 

TBarCYa

Senior Chief Petty Officer
Joined
Apr 13, 2005
Messages
781
Yeah.... Except that twice already I have forgotten to switch to the house battery when anchored and have been lucky enough to not end up with two dead batteries.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,417
Yeah.... Except that twice already I have forgotten to switch to the house battery when anchored and have been lucky enough to not end up with two dead batteries.

Got tired of that game long ago and installed a ACR. No more worries
 

TBarCYa

Senior Chief Petty Officer
Joined
Apr 13, 2005
Messages
781
I did something similar with continuous duty solenoids in a Jeep years ago...
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,966
Yep, ACR here too! No room for error. No worries...the way I think of it, I can enjoy boating a little more not having to worry if both of my batteries are charging.
 
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