Rigging a second battery

sjk984 · December 5, 2010

I want to add a second battery to my boat.

I would like to have the gps/sonar, kicker auto pilot, kicker throttle control and down riggers (2 digitrolls) to 1 and the motor starting to the other.

Is their awayto isolate the acc. battery from the starting battery and still have the alternator charge both.

And without one of the battery switches.

Thanks Steve

Nailer · December 6, 2010

A starter solenoid like the older fords used will do what your looking for.

A hot wire from the key will energize the solenoid to make contact to both batteries for starting, and running. Then when the key gets shut off, only one battery will be left connected.

jimcr · December 6, 2010

They make switches that will do what you are looking for. they can be set for 1 or 2 batterys or both. My first question would be does your kicker have an alternator? if not I would go for the switch route. that way you will always have at least one battery that is charged and ready to start the big motor.

The switches are less than 60.00 and you should be able to install it your self. The kicker I put on at the end of the season has one so for now I don't need to add a second battery.

Paulywood · December 6, 2010

I know there is another way to isolate Steve but I would have to look it up. But is there a reason you don't want to use the switch? I installed one on my last boat and have one as a factory install on the new one and they are great.

sjk984 · December 6, 2010

The only place I have to mount a switch is kind of in the way. I could use one if I have to but I was tring to find a way around it. But If a switch is the best way then that is what I am going to use.

Steve

GLF · December 6, 2010

Me personally......I would put the 2 batteries in parallel. After a day of running the riggers up and down and powering all of the electronics, it puts a lot of drain on the battery.

How long will a battery last that is continuously deep drained and recharged?

Paulywood · December 6, 2010

Mike my second battery is never down much after a day of fishing. I usually flip the switch over before running back in then check it at home. It is almost always fully charged. I have even come back without recharging and it never needs more than a short charge at home. The riggers and electronics don't pull that much juice.

jimcr · December 6, 2010

Me personally......I would put the 2 batteries in parallel. After a day of running the riggers up and down and powering all of the electronics, it puts a lot of drain on the battery.
How long will a battery last that is continuously deep drained and recharged?

So lets say one of your batterys goes out Mike, Being that they are in Parallel would you still be able to restart while out on the water. Your still going to have 12 volts but are you going to have enough amperage to start the big motor.

That being said the switches have the ability to run with both batterys in parallel or batt one or batt 2.

GLF · December 6, 2010

So lets say one of your batterys goes out Mike, Being that they are in Parallel would you still be able to restart while out on the water. Your still going to have 12 volts but are you going to have enough amperage to start the big motor.
That being said the switches have the ability to run with both batterys in parallel or batt one or batt 2.

If I can not get a motor to start, it is not a battery issue. I have 4 batteries on my boat, 2 in parallel for each engine. I also have a bypass solenoid that will start the other engine if needed.

I run 3 riggers with 15lb balls. If I am running the riggers up and down alot while running the motor that the downriggers are not connected to, I notice them slowing down on the way up. I run Big Jon Brutes, and they draw a fair amount of current.

Here is the issue I see with switching from 1 battery to 2 with a switch. "If" the batteries are not equally charged, I "believe" the batteries will try to balance themselves. One will be drained, and the other will charge.

sjk984 · December 6, 2010

I have not had an issue this year with 1 and have had a small set of cables made to hook to my trolling motor battery if I ever have a problem. I only have a 50hp main so that doesn't take much to turn over. This year I am adding an auto pilot and throttle control. Do you guys think I would be OK with the set up I have or am I over thinking this.

I am able to pull start the engine in an emergency. I have done it in the drive way to see how hard it was.

Steve

jimcr · December 6, 2010

If I can not get a motor to start, it is not a battery issue. I have 4 batteries on my boat, 2 in parallel for each engine. I also have a bypass solenoid that will start the other engine if needed.
I run 3 riggers with 15lb balls. If I am running the riggers up and down alot while running the motor that the downriggers are not connected to, I notice them slowing down on the way up. I run Big Jon Brutes, and they draw a fair amount of current.

Here is the issue I see with switching from 1 battery to 2 with a switch. "If" the batteries are not equally charged, I "believe" the batteries will try to balance themselves. One will be drained, and the other will charge.

I see you point Mike but at the same time the charging circuit should be able to make up the difference.

Does the motor running charge the batteries that are not in service?

Sorry if this is taking this another direction.

My father when he was in the Navy was incharge of the batterys on the ship I will check with him and see what he thinks. I know you have it right Mike your boat was most likely designed that way.

Paulywood · December 6, 2010

Mike, when I am fishing I have the switch set on 1 battery. That isolates the main battery from the secondary so that the main battery is the only one that is charging. That way the boat will always start and if the second battery is low it won't draw from the first. Steve, I would definitely add the second battery. It's better to be safe than sorry out on the water.

GLF · December 7, 2010

Here is the issue I see with switching from 1 battery to 2 with a switch. "If" the batteries are not equally charged, I "believe" the batteries will try to balance themselves. One will be drained, and the other will charge.

This part is a little confusing. My supervisor walked in on me when I was typing this, and I did not get a chance to preview the post. I also took out the "believe" part of it, because I am 99.9% sure of this!

Remember....I am talking about hooking up batteries in parallel. If the batteries are not equally charged, and the switch is switched from 1 battery to 2 batteries, the batteries will try to balance themselves. One will be drained, and the other will charge, untill they reach the same level of charge.

sjk984 · December 7, 2010

This may sound stupid but when the batteries do equilize wont you still have the same voltage still be available. The switch just makes it so you can't drain both batteries.

Also in most cases with larger boats a stern drive alternator will produce enough amps to keep up. In my boat I will be running everything of off batteries with no charging while I'm trolling.

Priority1 · December 7, 2010

Charging systems on IOs and Inboards are similar to a cars charging system. Most outboards have a very limited charging system. At idle the main outboard will put out next to nothing and a kicker will put out less.

What Mike was saying if you run two batteries at the same time and one is almost dead and the other fully charged you'll end up with the equivalent of two half charged batteries.

1mainiac · December 7, 2010

You can purchase a battery isolator which is basically a set of diodes that control the direction of electrical flow. It has to be matched to the size of the charging system in amp rating this allows one alternator to charge multiple battery banks. If you are running a kicker with a charging system I would put it on it's own battery and run the riggers and electronics off it. Put your main engine on a separate battery and use it for starting only. Run the output from your main engine to the isolator input ant a output from each side of the isolator to each battery bank. Doing this will give you 2 separate battery systems that can both be charged by the main engine. And no switch's to flip or remember when you run out on the main engine it will make sure the aux battery is charged and when you run back it will again top it off. As to running batteries in parallel there are pro's and con's the first being that the batteries have to be closely matched so they can equalize correctly mismatched batteries in a bank are only as good as the worst battery. I will not replace a single battery in a set we change the set it just avoids problems. The Pro side is you can double the capacity of your system which reduces the chances of having a problem to begin with. Feel free to contact me and I can go into more detail.

sjk984 · December 7, 2010

What Mike was saying if you run two batteries at the same time and one is almost dead and the other fully charged you'll end up with the equivalent of two half charged batteries.

Priority1 · December 7, 2010

What Mike was saying if you run two batteries at the same time and one is almost dead and the other fully charged you'll end up with the equivalent of two half charged batteries.

So if I drain my acc. battery to 4 volts and switch to a battery with 12 volts. They will equilize at 8 voltz each but since now that the battery switch is on all wont I still have 16 voltz available for starting.

I do realize I may not be getting this

When the switch is on ALL will the batteries be parallel

GLF · December 7, 2010

What Mike was saying if you run two batteries at the same time and one is almost dead and the other fully charged you'll end up with the equivalent of two half charged batteries.
So if I drain my acc. battery to 4 volts and switch to a battery with 12 volts. They will equilize at 8 voltz each but since now that the battery switch is on all wont I still have 16 voltz available for starting.
I do realize I may not be getting this
When the switch is on ALL will the batteries be parallel

The only way you would have 16 volts, is if your batteries were in series. Voltage does not add up when batteries are in parallel.

I run my batteries in matched pairs like Jim. If one goes bad, I swap both of them.

sjk984 · December 7, 2010

Got it. thanks.

Priority1 · December 7, 2010

I don't mean any disrespect but you probably should have some help when you do this wiring or at least have someone check your work. A basic understanding of circuits is required. If you need any help there is probably someone here that is close by that can help. It could save you $$$$$.

sjk984 · December 7, 2010

I don't mean any disrespect but you probably should have some help when you do this wiring or at least have someone check your work. A basic understanding of circuits is required. If you need any help there is probably someone here that is close by that can help. It could save you $$$$$.

Thats funny I was just contempaltng having it done at the marina He usually takes pretty good csre of me when I do have to take it in I really appreciate the help.

jimcr · December 7, 2010

Well this is what most of you are looking for. It describes it pretty well.

http://www.bluewatermarinesvc.com/html/bat_isolator.html

Priority1 · December 7, 2010

Maybe watch him do it. It is not rocket science but it must be done correctly. The CG does check electrical, but most important is your safety and the safety of your crew. If I lived closer I would help you and have you help me with something.