Battery Selector and Hookup Question
 

I just had a question regarding Dual batteries and using a selector switch. I looked in the search but couldnt find anything related to exactly what is happening with mine.
I have a battery selector switch that is OFF, 1, 2, 1+2 .
I have the main battery which is a Deka Marine series battery. The engine, electronics, and amps are connected to this one. My secondary battery is a just incase battery and its an Oreilly Marine Master series. I wanted to have this one to crank the boat if we sit for a long time and run down battery one.
The switch came with the boat and battery 1 was already wired. I installed battery 2 and ran it this way. I unbolted the switch, connected the "2" post to the positive of battery 2. I took the negative on battery 2 and connected it into battery 1. From what I have read this is acceptable and it should work the proper way. Here is the weird thing. Nothing is on battery 2. I was playing the radio and testing everything on battery 1. I switched to battery 2 and everything kept playing and the LEDs were still on. I was under the impression everything would turn off since nothing was connected.
If it's wired correctly I am ok with it being this way, I just want to make sure I have the second battery as a cranking battery and that we arent pulling power off it too.
I was just thinking this didnt sound right and didnt really make sense that everything still ran even in just "2" selection.
Thanks for your help in advance.

Mine is hooked up the same way as yours. Nothing wrong with having it like that I have not had any issues with mine. What ever you have connected to the common terminal on the switch will run off either battery.

One piece of advice is do not switch the switch with the boat running. I am going to assume the boat was not running when you did this but, if it was it could kill your alternator and no telling what else.

yea you have it right, you just made a circut when you connected them thats why everything still works

If the electronic device is connected directly to Batt1, it will continue to work regardless of the switch's position.

If the electronic device is connected in some way to the switch terminal "COMM", then it will work as long as the switch is in either 1 or 2. look at it this way, the switch is not turning the batteries on or off. They always have voltage, but the what the switch is doing is making or breaking between the battery(s) and what ever is connected to the "Comm" post.

Ok, thanks guys, I just wanted to make sure I had it all correct and that I wouldnt get stranded because it was pulling off both if it was switched to 1. I think I did have in my mind that it turned the battery "off" completely and only used the one it was selected on.
Aj, no the motor hasnt been cranked at all, except from the factory for lake test. I have read multiple threads saying dont do it while the motor is running. I figure while we are riding I will use 1+2 and then when we stop to anchor up, I will switch it to 1 so it doesnt pull from 2.
I figured it completed the circuit so I wasnt sure how the selector worked or treated it as in if the selector broke the circuit to all devices attached to that battery if it was on another selection.
Nothing worse that being stranded because of a dead battery. I usually keep a jump pack on board too, just incase my "just incase solution" fails too :p

I personally wouldn't hook it up the way you have it but that is just me. The computer and standard electronics should all be hooked up through the wiring harness back by the engine. Leave that how it is unless you want to pull the deck power off of that bus bar and hook to the stereo bank. Then I would hook up the amps/deck to the stereo bank. This way anytime you stop and listen to your stereo you can turn the battery selector switch to position 1(starting battery) and you stereo will only drain you stereo bank. Then you can start the the boat just using the starting battery and once it is up and running turn the switch back to both so both battery banks are being charged. By the way you are ok switching positions on the selector switch as long as it is a "make before break" style switch. This means that before it breaks the circuit you are turning off it completes the circuit you are turning on. What you want to avoid is turning the switch off while the boat is running and there is a huge load on the alternator. This blows diodes because the alternator is putting out most of it's available amps and cutting the load in a split second doesn't give it time to wind down. Those rush amps with no where to go blows the diodes. The only problem I see with the system I am talking about is that if you wanted to fully disconnect the batteries in the winter you would need to manually pull off the ground or positive terminal or put in some sort of battery disconnect switch between the stereo bank and the amps.

Here is a diagram. You see it has the back of the switch. There should be 3 large terminals. One for common and then one each for battery 1 and battery 2. This diagram shows a 2 bank system while using 3 batteries. It also shows a 2 bank battery charger at the bottom of the diagram. Notice all 3 batteries negative terminal are connected to each other but the positive terminals are only hooked together on battery 2 and 3. This means battery 2 and 3 are wired in parallel and battery one is a stand alone battery unless the switch is in the "both" position and at that point all 3 batteries are in parallel.

Be carefull saying that it is o.k. to change the switch with the boat running. There is a reason they make switches with an alternator field. If you have one of those it is alright but I dought it came factory with one.

That is why I mentioned a switch that make sure your selector switch makes the new connection before breaking the old one. If you go from position 1 to position both, both to 2 or any combination that doens't involve completely opening/breaking the circuit you are fine.

Why risk it. Install a ACR so both batteries will charge no mater what the switch is set to.

Polarbill, thanks for the diagram and advice. When we picked it up, everything was run into one big Positive and negative. The factory amp was run off that and the deck power was too. Since it was bundled in, I wasnt going to pull apart the harness and try to find them so thats why I decided to run Amp 1, 2, and 3 off the main battery.
I figured as long as its not on "2" when we sit and listen to music , the second batt is fine as long as I switch it to 1+2 when running. I don't plan to change it while the engine is running for sure. I dont know what came factory or what they have in place but i'm just going to play it safe.

I agree with using some sort of smart realy/combinor/seperator. The main reasons I recommend those are SOME of them are cheap(Sure Power 1314/1315), they are incredibly easy to hook up, and basically do what a selector switch does but automatically. They also protect the alternator by charging in steps so your alternator isn't running full blast for hours. A selector switch will still work just fine if you know how to use it. In my opinion a selector switch's biggest downfall is that you have to remember to switch it and when to switch it. Most people buy boats to enjoy them. Not to have to worry about flipping switches. Not that it is that hard in a small ski boat. Here is an example of a good quality selector switch.

http://www.jamestowndistributors.com...?pid=2769&BASE

Here is the one I use.
http://www.westmarine.com/webapp/wcs...tial/0/0?N=377 710&Ne=0&Ntt=blue-sea&Ntk=Primary Search&Ntx=mode matchallpartial&Nao=0&Ns=0&keyword=blue-sea&isLTokenURL=true&storeNum=5002&subdeptNum=9&cl assNum=12106

This is the Sure Power I use. The advantage to this one is that it can disconnect the 2 banks even when the boat is running. It also has a start assist option so if you know your starting battery is toast you can flip a switch and combine all batteries for starting. Another nice thing is that it gives charging priority to the starting battery. It is also 30-40 bucks cheaper than the Blue Sea relay.


http://surepower.com/pdf/separatorinterconnect.pdf

Some options I will def look into. We used to have an Isolator in the I/O and it worked well. It only turned on once the key turned to ignition but when the key was off, it completely isolated the other battery. It was an RV/Boat isolator and worked well. May have to see about getting that again. It hooked to the alternator wire and I guess sensed the voltages as well so it wasn't running it all the time full force.
Thanks guys for giving me a heads up on some different ideas. For now (gotta get out on the water first and break in the engine) I may just stick with how I have it. I will probably run on it like it is until the end of the season and then evaluate some other options :)
I'm not certain which one is in mine. Didn't look at it close enough, I think its a Perko though.

Did you have an isolator or a voltage sensing relay? Isolator's are very simple but pose some problems. First they have an inherent voltage drop of about 1 volt. If your alternator is putting out 14.5 your batteries are only going to get 13.5 if all your cables are in good shape and the run isn't too long. This can negatively affect battery life as the batteries will never completely charge. Also an isolator doesn't give a priority to your starting battery. For example, if you turn your boat off and listen to your stereo for 3 hours and completely drain your stereo battery the isolator is going to send all the current to the stereo bank as the current goes on the path of least resistance with an isolator. This means that you could run your boat all day after you drain the stereo battery and your starting battery will not get any current to it until it is drained less than the stereo battery or untill the stereo battery is charged up to the level of the starting battery.

Yeah, it was an isolator and not a voltage sensing. I knew about the volt drop issue and that part but wasnt aware it wouldnt charge the other until it dropped below the others voltage too. On the other boat, I rewired the radio and all amps and LEDs to be on the second battery and battery 1 was a charging one. Explains why I went through the factory battery within a year. Seems like it was always dead and I had to put it on the charger. I thought it had a bad cell, never thought it wasnt getting correct charge.