Dual Battery Questions

[hostage]

so I am thinking of adding a battery to my boat. I currently own a 19ft Maxum Cuddy w/ a 4.3L Mercusier. It seems hard to find a spot for it, though I am thinking of putting in the bow.

Anyway, I have a car battery as my sole battery right now. The question I have as follow:

1) Can I add a deep cycle marine battery for radio, lights, and fans. At the same time allow it to be charged by the alternator?
2) Any issue putting it in the bow as I don't see much space for the battery in stern?
3) Feel free to give me any other tips.

Thanks in advance,

Hostage

 

[LippCJ7]

Re: Dual Battery Questions

1) Yes but I advise to keep your batteries pretty close in Capacity if not exactly the same from the manufacturer on, opinions will vary but this is how I have done it for many many years, the auto manufacturers do it the same way I see no reason to tempt fate.

2)no problem at all, just costs money in cables large enough to carry the load for that distance. when your talking about the load capacity of wire, the longer the distance the larger the cable, smaller cable can carry the same load as larger cable when it is a very short distance, typically large load bearing battery cables only run 5' or less, they are usually 4 gauge or bigger, to put the battery in the bow is going to take some decent sized cables, we just have to determine the load they will be carrying, do you ever think you will need the battery in the bow to start your motor? what size are the cables in your boat now(should be clearly labeled on the side of the wire)?

3) I believe that you should use your batteries as one system but be able to separate them at will via a multiple battery switch, you decide when and where to separate them, if your planning on moving one to the bow then why not maximize the room you have where the one you have now is and upgrade it as well? Some don't care to do this and simply want switching to be automatic and go with an ACR or similar system, its completely up to you.

 

[Chris1956]

Re: Dual Battery Questions

Marine batteries are supposed to be a bit tougher than auto batteries, in order to survive the pounding a boat will give them. If you put the battery in the bow, it will take a pounding. It would be far better to put one battery on each side of the motor, or two on the same side of the motor. is the PTT in the way?

How about using a single Marine deepcycle/starting combo battery of the 27 Series? You will still need to watch how much juice you use, but will have more reserve.

If you want to use two batteries, a battery switch is a real good idea.

Never set the switch to off when the motor is running. That can blow the alternator diodes. Alternatively you may use a battery combiner and wire the house load to the deep cycle battery. You will need to wire the alternator charging output directly to the battery combiner.

 

[LippCJ7]

Re: Dual Battery Questions

I went back over this and came up with another concern, you have a cuddy, and that eliminates the bow for me, batteries give off poisonous gasses so you would have to be certain your mounting location would vent to the outside rather then in the cuddy.

 

[hostage]

Re: Dual Battery Questions

I think next time I get a battery, I will get a large deep cycle marine grade battery. Instead of having a second battery, I might just get one of those jump starting things.

 

[Silvertip]

Re: Dual Battery Questions

Marine batteries are supposed to be a bit tougher than auto batteries, in order to survive the pounding a boat will give them. If you put the battery in the bow, it will take a pounding. It would be far better to put one battery on each side of the motor, or two on the same side of the motor. is the PTT in the way?

How about using a single Marine deepcycle/starting combo battery of the 27 Series? You will still need to watch how much juice you use, but will have more reserve.

If you want to use two batteries, a battery switch is a real good idea.

Never set the switch to off when the motor is running. That can blow the alternator diodes. Alternatively you may use a battery combiner and wire the house load to the deep cycle battery. You will need to wire the alternator charging output directly to the battery combiner.

Combiners are very "old school". Automatic charge relays (ACR) is the way to go or else use a dual battery switch (or both if you prefer).

 

[Silvertip]

Re: Dual Battery Questions

I think next time I get a battery, I will get a large deep cycle marine grade battery. Instead of having a second battery, I might just get one of those jump starting things.

Very wise choice since you do not have any high current draw items that would pose a risk of draining the battery. Paying attention to what you have turned on is the key to preventing a dead starting battery. Keeping the jump start box charged is the other issue. It does no good if it is dead as well.