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josh_tn

Ignition wire for dual batteries

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josh_tn

Ok, I just got my relay for setting up dual batteries. I have not worked out all the details yet and want to get everything figured out before I start the install. In order for the isolation to be automatic I need a true ignition wire to operate the relay. It will be located in the rear of the boat close to the batteries. Is there already one back there that I can use or will I need to run one from the dash. If I need to run one, where should I take it from? Can I get it directly from the back of the key switch?

Thanks.

Josh

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D-GOOSE

First off there would be on clear cut answer to your ?? unless a person has the same boat. With that said.

I would look for one that is coming off the fuse block. Plus I would also I would look for ign power at the fuse block. Put a inline fuse on the wire to your isolator. I will look more at my boat tonight to see what I can see or think of.

If you do go off the eng side of things you may be back feeding some thing.

Ps can you give us more info on your boat.

Pss the isolator is the best way to go IMO for dual batt.

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Jimmy Buffett

What type of relay do you have? Most don't require much current to close. There may be a way to splice into another wire, but the cleanest approach is to run a new wire (doesn't have to be big guage) from the ignition switch to the relay.

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josh_tn

Sorry I didn't give more info earlier. The boat is a '97 Sunsetter VLX. The battery is currently in the rear passenger side compartment beside the engine. There is also a ballast bag in there, so I hope to move the batteries to a new location. I'm looking at putting them under the rear seat if they will fit. If so, I will also put the relay there. The boat has a shower, heater, and 2 speaker amps that were all installed later by one of the owners. See below for what I have figured out so far about the current wiring.

Ok, I just got back from the boat. (I was replacing the rear ballast hoses). I took a look at the current connections to the battery. It appears that the starter and all accessories run off of one large gauge cable to the battery. It looks like it is just going to the starter, but I pulled everything else from the battery and all accessories still worked. The other 3 wires to the battery appear to be for the tower speaker amp, the cabin speaker amp, and the alternate battery terminal under the rear seat. So how am I going to isolate my starting battery to just the starter and have everything else run off the second battery? I could just run the 2 amps off of the second battery since they are probably the most power consuming devices but I would really like to isolate the main battery to just the starter if possible.

It looks like it would be really easy to just run a new ignition wire from the switch now that I've looked at it closer.

I appreciate everyones help on this.

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Jimmy Buffett

Because your relay combines the two batteries, it won't matter whether you separate the accessories from the starter or just put them all on the same battery. Once you turn the ignition and combine the two batteries with the relay, it's all the same and it doesn't matter where everything is hooked up at that point. The only way to get a benefit from putting the accessories on one battery and the starter on the other, is to have a battery switch (like a Perko) or a battery isolator (Hellroaring) that will isolate the batteries when discharging yet allow both to charge.

If you're using a relay, just run a ground cable between the two negative battery posts and a positive cable from the positive post on the batteries to the positive posts on the relay. Run your ignition wire to the relay and your relay ground and you're all set.

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josh_tn
Because your relay combines the two batteries, it won't matter whether you separate the accessories from the starter or just put them all on the same battery.  Once you turn the ignition and combine the two batteries with the relay, it's all the same and it doesn't matter where everything is hooked up at that point.  The only way to get a benefit from putting the accessories on one battery and the starter on the other, is to have a battery switch (like a Perko) or a battery isolator (Hellroaring) that will isolate the batteries when discharging yet allow both to charge.

If you're using a relay, just run a ground cable between the two negative battery posts and a positive cable from the positive post on the batteries to the positive posts on the relay.  Run your ignition wire to the relay and your relay ground and you're all set.

The batteries will be isolated when the ignition is off which is my main reason for going with dual batteries. If I sit for a while without the engine running, the HU, CD changer and any other accessory I use will be draining my starting battery instead of the second battery. I'm sure that the HU and CD changer will not drain much from the battery since all the speakers in the boat are running off of the 2 amps, but there is more of a chance or running down both batteries that way.

This is the way I understand this setup to work. Correct me if I'm wrong.

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Jimmy Buffett
The batteries will be isolated when the ignition is off which is my main reason for going with dual batteries.

Yes.

If I sit for a while without the engine running, the HU, CD changer and any other accessory I use will be draining my starting battery instead of the second battery.  I'm sure that the HU and CD changer will not drain much from the battery since all the speakers in the boat are running off of the 2 amps, but there is more of a chance or running down both batteries that way.

Not sure what you mean. The accessories will drain whatever battery they're connected to, and for you it doesn't matter which one that is. My post above was in response to your question about putting the accessories on one battery and the starter on the other. This is unnecessary with a relay because once you turn the key the batteries are combined. The reason you would want to separate them (and use a Perko or an isolator) is so that your starting battery is always 100% fresh and you can start the boat with a fully charged battery. With the relay, you can't do that because the batteries will be combined and if one is drained it will draw charge from the other one until they equalize. Since the 2 batteries will equalize, it doesn't matter if you drain one all the way down or drain both batteries half way. Just leave everything hooked up the way it is and add a second battery with the relay.

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D-GOOSE

josh

I'm lost know. What are you using for you isolator. I.E. relay, perko switch, or a isolator?

If your having two batt's just hook up the starter wire to one batt and all others to the 2nd batt.

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josh_tn
The batteries will be isolated when the ignition is off which is my main reason for going with dual batteries.

Yes.

If I sit for a while without the engine running, the HU, CD changer and any other accessory I use will be draining my starting battery instead of the second battery.  I'm sure that the HU and CD changer will not drain much from the battery since all the speakers in the boat are running off of the 2 amps, but there is more of a chance or running down both batteries that way.

Not sure what you mean. The accessories will drain whatever battery they're connected to, and for you it doesn't matter which one that is. My post above was in response to your question about putting the accessories on one battery and the starter on the other. This is unnecessary with a relay because once you turn the key the batteries are combined. The reason you would want to separate them (and use a Perko or an isolator) is so that your starting battery is always 100% fresh and you can start the boat with a fully charged battery. With the relay, you can't do that because the batteries will be combined and if one is drained it will draw charge from the other one until they equalize. Since the 2 batteries will equalize, it doesn't matter if you drain one all the way down or drain both batteries half way. Just leave everything hooked up the way it is and add a second battery with the relay.

Ok, I think I see what you mean now. You're saying that in the few seconds that I turn the key to start the battery, both will equalize? I guess I figured that it would take longer than that. Possibly some sort of diode arrangement could fix this? Seems like it would defeat the purpose of having dual batteries if I could still run them down enough to not be able to start the boat.

josh

I'm lost know. What are you using for you isolator. I.E.  relay, perko switch, or a isolator?

If your having two batt's just hook up the starter wire to one batt and all others to the 2nd batt.

I am using a relay. Its a 200 amp Stinger relay. The original question I asked was that I could not find just a starter wire. The only wire connected to the battery(other than the amps) was for everything(starter, alt., and all accessories). They are not separated at the battery.

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josh_tn
Since the 2 batteries will equalize, it doesn't matter if you drain one all the way down or drain both batteries half way.  Just leave everything hooked up the way it is and add a second battery with the relay.

So then what is the purpose of the relay? Would it not be easier to just connect the 2 batteries together all the time? What would the advantage be of having them separate when not running if they are just going to equalize before you can start the boat?

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SacRiverRat
Since the 2 batteries will equalize, it doesn't matter if you drain one all the way down or drain both batteries half way.  Just leave everything hooked up the way it is and add a second battery with the relay.

So then what is the purpose of the relay? Would it not be easier to just connect the 2 batteries together all the time? What would the advantage be of having them separate when not running if they are just going to equalize before you can start the boat?

That is why most don't connect it that way - have the battery separated by a combiner, so they charge together, but one battery powers the accessories (stereo) and one starts the boat. That is the point of having two right?

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josh_tn

Yeah, that was my intention anyway.

I was under the impression that a high current relay would do the same thing as the combiner only it would be automatic instead of a manual switch. The only problem is that operating the relay with an ignition wire will cause the batteries to combine before starting the boat instead of after the boat is running (If I understood the earlier posts correctly).

Is there some other wire that would only operate the relay after the boat is running?

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bigD

Josh,

you won't have a problem with the relay unless run your battery dead then turn the key on and let it sit there with out starting the engine and let it drain your good battery.

Most of the big systems I've seen have relay's to separate the stereo batteries when the ignition is off. Their simple and they work fine if your not stupid, most of the fishing boats I've seen have Perko's ;)

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D-GOOSE

the diode arrangement that you are looking for is called a (isolator, Hellroaring) The isolator will only let power in and not out. OOOOO were is that site address when you need it.

Well this is how it works.

The isolator will have three post (or you may need the four post to ignite the alt.) the center is for alt power wire in, one side go's to batt 1 and the other side go's to batt 2. From there you run what you want off of each batt.

Big D is right about not letting the eng switch being on to long befor starting. Perko is used in a ton of duel batt set ups.

But as I said befor I like the Isolator best. just my 2c

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Jimmy Buffett

Hellroaring website

Big D is right, the batteries don't equalize instantly but the longer you let it sit the more charge transfers b/t batteries.

If you want to make your relay a manual switch rather than automatic with the ignition, just run a wire from a dash switch to the relay instead of the ignition switch. Then you'll have to remember to turn it on and off as needed, rather than having it automatic.

The only sure-fire way to make sure you have one starting battery is a true isolator.

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josh_tn

Ok, so it seems like the setup I have now with the relay will work fine as long as I am careful not to keep the ignition switch in the 'on' position for too long before starting.

I also thought about the idea of running a separate switch on the dash to operate the relay but that would essentially defeat the purpose of going with the relay over the perko. It is still an option at this point though.

What about the question of getting the starting battery wired just to the starter. As I mentioned earlier there is a single large gauge wire that goes to the alternator, starter, and all accessories. Is there an easy way to separate the starter on a separate wire to run to the starting battery? Is it worth the trouble, or would you just leave it as is and run the 2 amps from the second battery and leave everything else on the starting battery?

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Jimmy Buffett

I'd probably just leave it like it is rather than rewiring for the starter. Unless you mistakenly leave the heater, blower, bilge etc. running, the headunit and CD Changer aren't likely to drain the battery themselves. Main draws are from the amps, you should be fine.

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josh_tn
I'd probably just leave it like it is rather than rewiring for the starter.  Unless you mistakenly leave the heater, blower, bilge etc. running, the headunit and CD Changer aren't likely to drain the battery themselves.  Main draws are from the amps, you should be fine.

Thanks. Sounds like I am ready for the install now. Thanks for everyone's help. I will be sure and post some pics when I finish.

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josh_tn

Well, I broke down and bought two Optimas today. I was hoping to place one under each side of the rear seat due to size constraints under there. After getting the batteries, I noticed that they would actually both fit on one side which would greatly reduce the wiring installation. My question is, do you think there is enough room for the wiring with both batteries in one side? Any other foreseeable problems? I could move the relay out of there if I need a little more room for running wires. Let me know what you think.

optimas%20003.jpg

Also, what are your thoughts on the best way to keep them stationary. Some kind of blocks or maybe some straps of some kind?

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dmx434343

ive seen most people screw theres down, i dont have mine yet so i am wondering what you do as well.

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josh_tn
ive seen most people screw theres down, i dont have mine yet so i am wondering what you do as well.

Well, I don't have the boat anymore but I ended up not fastening them at all. Laying on their side like that on the carpet the lip seemed to keep them from moving around at all. With the heavy gauge cabling installed it also helped keep them stationary. It might not work well if you have them in a more open space but it worked for me.

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Faceplant409
Well, I broke down and bought two Optimas today. I was hoping to place one under each side of the rear seat due to size constraints under there. After getting the batteries, I noticed that they would actually both fit on one side which would greatly reduce the wiring installation. My question is, do you think there is enough room for the wiring with both batteries in one side? Any other foreseeable problems? I could move the relay out of there if I need a little more room for running wires. Let me know what you think.

optimas%20003.jpg

Also, what are your thoughts on the best way to keep them stationary. Some kind of blocks or maybe some straps of some kind?

Josh, what's with the aluminum thingey hinged over the rear batt???

BTW on my last 2 boats I used a West marine combiner to combine the batts when charging, they discharge separately though (with key off -stereo and amps are on dash switch, not Ign switch.). I left all the "boat stuff" on the starting batt, but all the extras on the 2nd one. Have never had a problem.

Pat

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