Electronic systems and multiple batteries

Strychn9ne

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Aug 27, 2016
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Hey everyone! Just got a new to me 1965 Starcraft Siren recently. This is my first true boat, all I've owned until now are aluminum row boats, so I'm not familiar with many of the systems used on vessels such as cruisers and bass boats.

So I've been going through this boat's simple electrical system and have a few questions. I want to run most everything on it's own battery and try to keep the starting battery for just the engine. I have a nice little crawl space under the bow that would be perfect for installing the extra batteries, while keeping the main one at the rear. My idea is to run the fish finder on it's own battery, the lighting and accessories (Small air horn, 12v outlets, maybe a small stereo, etc.) on their own battery. Has anyone tried this set up before?

I have just the stalk light and red/green for now, but would like to install 2 or 3 small deck lights as well. Now I know the fish finder can run fine on a small 12v 7ah battery for days without a re charge, but what about all the other things? Would I need a full sized battery for that, or could I get away with a smaller, cheaper one such as an AGM cycle sized battery? Also, would I have to ground the second accessory battery, or could I just leave it connected only to the accessories in it's own little world like the fish finder battery?
 

MH Hawker

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most run a 2 battery system with a selector switch for those very reasons
 

gm280

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Yes two battery setup is the norm. Remember, the more batteries, the more you have to charge up and maintain as well. Most use a battery for the engine and even all the accessories. And the second battery for the trolling motor. But you can chose to split up batteries and their usage however you like. It is your boat after all. If you are going for a two battery setup, install a battery selector switch for those occasions you run one battery down too far and need to crank the engine. JMHO
 

Starcraft5834

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I too run two batteries.. main on engine and related, separate battery on fish finder/gps.. if one konks out, u have the other
 

Bondo

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I too run two batteries.. main on engine and related, separate battery on fish finder/gps.. if one konks out, u have the other

Ayuh,.... Reason enough right There not to putz 'round with motorcycle batteries,....
 

muc

"Retired" Association of Marine Technicians...
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Jul 7, 2004
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You don't say what engine you have. But if it's an old outboard, they can have charging systems that don't have voltage regulator. If it is one of those types, the voltage can get high enough to fry a new style depth finder and bake an AGM battery to crisp.
If you have a good charging system I recommend the normal 2 battery set up with a selector switch. I tell my customers with this set up to use battery #2 on even numbered days and battery#1 on odd numbered days. That way both batts get used and stay fresh.
 

Strychn9ne

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Aug 27, 2016
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Thanks for the responses everyone! Doh, I forgot to mention the engine! It's a 1965 Kiekhaefer Merc 35 hp with electric start and choke. I'm pretty sure it does have it's own charging system. I'm currently running a Delco flooded type marine battery. No hydraulics, everything's manual. My lights are wired directly to the Delco with a single in line fuse. My depth finder is a brand new Humminbird Piranhamax 197c.

So, from what I've gathered so far, running the depth finder on it's own small battery is likely the best way to go to prevent possible damage and/or constant blown fuses. I have an AC/DC hobby charger for my RC car batteries that can also charge lead acid at a max rate of 6 amps, and it works very well for those smaller 7-9ah 12v ones. I do plan on getting a transom mount trolling motor eventually, so I'm thinking that running the lights to the starting battery and just installing a battery selector when I get the troller and a second starting battery is best course here. I'm also thinking of installing a fuse block under the dash to clean up the wiring in the battery box a bit, but I'm gonna run the depth finder on it's own in line fuse I think.

Alternating battery usage, good idea there! I'll remember that one.
 

Silvertip

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Sep 22, 2003
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For trolling motor operation you need a marine DEEP CYCLE battery. Starting batteries do not last long under the high discharge rate of a trolling motor.
 

Strychn9ne

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Aug 27, 2016
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Hmm good to know. How can one tell if a battery is a deep cycle one? I will buy a new one for the trolling motor and make sure it's deep cycle, but I'm curious about the one I have currently. It says AC Delco Marine on it, and has a 550 CCA and 86 AH rating. Are all batteries labelled for marine use deep cycle?
 

Starcraft5834

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Hmm good to know. How can one tell if a battery is a deep cycle one? I will buy a new one for the trolling motor and make sure it's deep cycle, but I'm curious about the one I have currently. It says AC Delco Marine on it, and has a 550 CCA and 86 AH rating. Are all batteries labelled for marine use deep cycle?


if it says Marine, i would assume it's deep cycle.... as I said, Ive got (2) batteries, both are "Marine", would not recommend using anything as a spare execpt deep cycle..
 

Strychn9ne

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Aug 27, 2016
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f its a sc delco vorage type its a deep cycle

Yes that is exactly what it is. Thanks for that. So deep cycle X2 it is. It won't be getting a trolling motor until next year, so no biggie now. I did get the trolling battery set up, just haven't mounted it or the control unit yet. Hopefully tomorrow it'll be all set to go! Thanks for the help/advice guys.
 
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