Battery Switch question

JimJames63

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Aug 8, 2021
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This is my first Cuddy boat, 1996 Larson Hampton 220. Fourth season with the boat, first summer we've over nighted. Have been overnighting almost every weekend, no problems yet, but worried about battery life etc. The battery config has me confused, I assume that one battery is the house battery, the other starter. There is a bunch of stuff hard wired behind the perko switch. As such, when I have the switch on Off, I still have full house electricity which seems odd? Also have trim tabs that will only work when switch is set to all. I wouldn't think anything would be hot, other than maybe the bilge on off? Any general advise as to how this stuff is supposed to be wired is appreciated.
 

Lou C

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Nov 10, 2002
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yep when the batt switch is off, the only thing that should be powered is the auto bilge switch. everything else should be off.
 

JimJames63

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yep when the batt switch is off, the only thing that should be powered is the auto bilge switch. everything else should be off.
That's what I thought, am I correct in thinking all accessories on house battery and starter only, on start battery?
 

JimJames63

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Next dumb question. What's best practices? start and cruise on "start" battery... then when anchoring switch to house battery? Have seen posts saying to stay away from "all/both" ???
 

alldodge

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Next dumb question. What's best practices? start and cruise on "start" battery... then when anchoring switch to house battery? Have seen posts saying to stay away from "all/both" ???
Yes

Unless you install a ACR, then don't worry about it

Two Bat one switch and ACR.jpg
 

Chris1956

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Mar 25, 2004
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A lot of people put all the load (except auto bilge pump)on the common post of the battery. When they get to anchorage they switch to odd battery on odd days and even battery on even days.
This allows a fully charged battery for starting in the AM, and shares the use across both batteries for even "wear".

There are marine starting/deep cycle combo batteries for this use.
 

Lou C

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That’s how mine is; I never separated the wiring so I just alternate batteries and use dual purpose group 27 batteries. I have the auto bilge wired directly to one of the batteries so I can shut the batteries off but still have the auto bilge switch & pump powered.
 

dingbat

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Nov 20, 2001
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Next dumb question. What's best practices? start and cruise on "start" battery... then when anchoring switch to house battery? Have seen posts saying to stay away from "all/both" ???
Best practice is to install an ACR with a ON-Off-Both switch and be done playing “battery switch roulette” altogether.

Battery wise, I divide everything into two camps.

Battery 1:
1. Everything I need to run the boat to get safely home (Motor, Trim Tabs, NMEA 2000 network, Chart plotter, Sonar, VHF and navigation lightening.)

Battery 2:
2. Auxiliary equipment......Sound system, any pumps, cabin and cockpit lights, back up and secondary navigation devices.

Not a fan of Marine Starting Batteries. They are a comprise between a Starting and a Deep Cycle battery. Don't perform either function particularly well.

It's my preference to use Deep cycles in both positions. No reason not to use a Starting battery on #1 but they don't hold up nearly as well (life expectancy) as a deep cycle when used as a cycled power source.

The trick is to find a deep cycle battery to meet the min. CCA requirements of your motor.
 

JimJames63

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Aug 8, 2021
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thanks Guys, rewired and added ACR today - no sparks :) so think I'm good to go. Thanks for the help.
 

sam am I

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Jun 26, 2013
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Battery 1:
1. Everything I need to run the boat to get safely home (Motor, Trim Tabs, NMEA 2000 network, Chart plotter, Sonar, VHF and navigation lightening.)

Battery 2:
2. Auxiliary equipment......Sound system, any pumps, cabin and cockpit lights, back up and secondary navigation devices.
Curious.....Why have the pump/s on the battery that being the sacrificial lamb w/could be most likely to be killed? e.g, the stupid dog left the audio/sound system and/or cockpit lights on and killed batt #2 flat......No pumps now?

Ya fire up the motor on safe batt #1 to of course get power to #2. BUT, how long does it take(alt current?) once up and running before a ACR stays sufficiently paralleled to the dead pump batt #2 to be able to pump water at a decent rate?

Do you run a Off/1/Both/2 or Off/On/Both switch?
 
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dingbat

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Curious.....Why have the pump/s on the battery that most likely being the sacrificial lamb w/could be killed? e.g, the stupid dog left the audio system and/or cockpit lights on and killed batt #2 flat......No pumps now?
The short answer....I don't need a "pump" to get back to the dock.

Why no pumps? Your kidding yourself if you think a bilge pump will keep you afloat with a hull breech. In times of trouble, power would best be used to extend the life of the VHF to call for help.

In reality, my biggest concern is a outright battery failure. Has happened twice on two different boats. The second failure started my crusade to wire critical components to a single battery.

I also run two identical deep cycle batteries. If push comes to shove, I can just swap batteries.
 
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