Marine Battery Setup...

[Mark Vanderhoof]

hey guys, im in the middle of a boat project and need to figure out my battery setup. the boat is powered by a 50hp electric start tiller so i need cranking amps to start that. i plan to have a transom mount trolling motor(12V), sonar/GPS, 6 LED cockpit lights, navigation lights and a lighter accessory plug for spotlights etc. i thought id use a deep cycle battery dedicated to the trolling motor and a dual purpose type battery such as an optima or cabelas AGM to run everything else. will that work? any suggestions? i also am considering using an on board charger that plugs into AC. id appreciate your suggestions as i dont have alot of experience with electrical systems. best, mark

 

[CK Jackson]

The way my boats have been rigged in the past is one (or two if I'm running a 24-volt system) deep cycle for the trolling motor(s), and a marine cranking battery that takes care of the outboard and everything else. An onboard two-bank charger is a good idea, as long as you plug it in...it will make sure you're ready to go at zero-dark hundred.

 

[Huntindave McCann]

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i thought id use a deep cycle battery dedicated to the trolling motor and a dual purpose type battery such as an optima or cabelas AGM to run everything else.

(A) Definite yes on the deep cycle for the trolling motor (B) no need for a dual purpose, use a marine starting battery designed for the high amp draw of your starter motor. Everything else on this circuit will be a very small draw for led lights, electronics, navigation lights and such. Even the spot light will not be an issue using a cranking battery for power.


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i also am considering using an on board charger that plugs into AC.

This is an option I now consider a "must have" on my boats.[/font] It will pay for itself in improved battery life alone plus the peace of mind knowing that your boat is always ready to go. Don't skimp on amps, I've been extremely happy with this unit ProSport II 20 It puts out 20 amps and has a circuit for the deep cycle and a circuit for the cranking battery. It comes with wiring instructions which are pretty straight forward.

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i dont have alot of experience with electrical systems.

They really are quite simple Mark, but I realize that not everyone is comfortable with electrical wiring. If you have doubts, this would be a case where it may be best to pay an expert or find a knowledgeable friend to help.[/font] You do not need an electrical fire on board a boat.

 

[JimG]

I think there's a book out there that is supposed to be a good reference. The 12 Volt Bible I think it's called.

The only thing I'll offer is make sure you buy marine grade wire and hardware.

 

[Capt. Dave Drewry]

~ I would highly recommend the dual battery set-up-- w/ cranking and deep cycle. All said here is great info... another item to suggest is a Blue Sea battery switches that fully seperates/ isolates the battery blocks. With these switches one battery is always saved for auxillary power ( charged by a seperate lead from the motor, and combined only when necessary ) The starter battery is isolated from the deep cycle circuit so there won't be interference with your electronics from cranking your motor- this power spike can be an issue with radios and some of the newer GPS units.

 

[Huntindave McCann]

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The starter battery is isolated from the deep cycle circuit so there won't be interference with your electronics from cranking your motor- this power spike can be an issue with radios and some of the newer GPS units.

Capt. Dave

So you would have only the starter motor wired to the cranking battery for one circuit. Then all the electronics and trolling motor wired to the deep cycle? If so, I strongly disagree and so do several boat factories.

As long as the cranking battery is in good condition and holds a proper charge, starting the motor will not be an issue for the onboard electronics. Very much like starting your car motor with all the gps and other electronic gadgets a car has on it. Yes I know that some things are bypassed on a car during the cranking phase but not all electronic circuits.

I certainly would not want any electronic gear hooked to the same battery as a trolling motor. The voltage in the deep cycle will drop significantly during the course of the day. There is no way any 50hp outboard will even begin to throw any kind of charge back into a deep cycle battery being drained by a trolling motor for periods of fishing. The trolling motor and deep cycle battery should be a stand alone circuit. If you drain the deep cycle during the course of the day the only thing you lose is the use of your trolling motor.

The electronics should be connected to the cranking battery.

Now if one has a much bigger boat and you can carry 3 or more batteries then sure, wire starter motor to one, wire electronics to another and wire trolling motor to yet another. Mark, however, is talking about a two battery system on a small boat utilizing a 50hp outboard.
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[Capt. Dave Drewry]

~ Dave M . I reread the original post and noticed the addition of the trolling motor. Certainly that motor would drain a deep cycle and I agree with your arguement. Most of the applications I have been involved in are larger boats where a third house battery would work well in those situations. An independent battery seperate of the cranking battery bank is best for the newer electronics , etc. but that is not always possible in smaller applications.

 

[Lee Chadwick]

I would agree as well with a seperate battery for the trolling motor. And HIGHLY recommend an on board charger.

 

[Bob B]

Mark,
these are a v. good on boat charger that we have used in dual and triple batt instals. http://www.dualpro.com/
They are a bit on the heavy side but in a bigger boat it is not an issue.

As for batt. type you will get a bunch of diff answers. We sell about 60 batteries each year. AGM we use LifeLine. Wet I like Trojan, Deka, and we have had good service from Interstate Marine line. Die Hard works too. Top is Rolls but all these need water added and can not be used on their sides. Only a couple of lead smelters left so most batteries come from the same place with box and label sold to each OEM. We are testing the Odyssey Battery in some boats, but they have been described as Alternator killers due to unbelievable low internal resistance. The regulation of the alternator never sees any resistance and just keeps hammering away(Equals massive Heat for the charge system)

If you keep the cable runs down you will be OK with the electronics on the start bat. The Troll batt will get discharged most likely and will not always be there for you to navigate. Some guys go with a mini motorcycle batt to power the GPS so it dosnt fall out when starting off the Start Batt.

If you like to read, Blue Seas has some very good stuff for charging, circuit protection, and switching.
http://bluesea.com/category/2/productline/overview/329
Also their wire size calculator is invaluable for getting the right size battery cable for the amperage you expect to use.
http://beta.circuitwizard.bluesea.com/

This may be more than you want to get into and can be done manually with a 1,Both,2 switch but Im not sure how much you are into the electrical layout of marine stuff.

If you have questions let me know.