Battery Switch on Boat

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I wasn't sure what forum to post this in so please move if necessary.

I would like to add an additional battery, with a battery switch, to our new pontoon boat. I've researched switches and will probably go with a Perko Battery Selector Swich.

https://cdn3.bigcommerce.com/s-6rtev5oww...80.1280.jpg?c=2

All I really want to do is have an extra battery aboard for Emergecy back-up that I can switch to if necessary and charge both while the engine is running. Except for starting power, and running courtesy and nav lights (which wouldn't be very often, if at all) the stereo radio would be the only other draw. I've read some articles where people will use one battery for starting and another battery for lights and/or accessories. I don't think I would need that and I might be wrong but that would also entail some rewiring. I'm thinking that all I need is a back-up I can switch too should my primary battery lose its charge. This a pontoon boat, not a yacht. Has anyone ever set up a battery switch like this? If so, how did you wire it up. Any thoughts and suggestions would be welcomed.
 
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I like that switch because it looks like it lets you run on either or both batteries.

You'll need to be smart about charging, cycling and balancing batteries with the approach you propose.
 
Originally Posted By: JHZR2
I like that switch because it looks like it lets you run on either or both batteries.

You'll need to be smart about charging, cycling and balancing batteries with the approach you propose.


That's just what I was thinking off the top of my head. I am open to suggestions. I am also limited with my options when not using the boat as far as keeping the batteries charged. There are no outlets for a battery charger at the covered marina we're at. So I'll probably have to remove one and take it home with me if there is any lengthy time away from the boat. Frustrating but that"s what we have to deal with.
 
You really just need one of these for $30.

"Human Factors" dictates you'll leave your switch int the wrong position someday.

This takes all the error out of it, and is automatic.

https://www.etrailer.com/Accessories-and-Parts/Deka/DW08770.html

dw08770_13_500.jpg
 
The product above is basically a diode, Those large heatsinks are basically dissipating alternator energy while that Diode/ electical check valve reduces the voltage to the second battery, slowing its recharge time significantly, and basically insuring it never gets fully recharged. People who care about their battery's longevity do not use diode based isolators.

The 1/2/BOTH/Off switches do have the human error factor, and if turned to OFF while the engine is running can blow the diodes in the alternator.

There are many dozens of automatic isolation products for secondary batteries out there.

I use the manual switch, the Blueseas 6007m. My previous switch that wore out after many years was a Guest brand.

For good battery life, the battery must be recharged to a full state of charge every so often and would prefer to always be cool, and 1005 charged. It takes no less than 3.5 hours for a healthy battery to go from 80% charged to 100% charged, and that is assuming a high absorption voltage of 14.4v+. So lesser voltages will increase that time considerably and that time also increases as the battery ages.

If thievery is not an issue where you store your boat, then consider a small solar panel to keep the batteries full, but even 10 watts with enough time is enough to seriously overcharge a battery that has no loads on it.

Some good reading:

https://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/

http://www.pbase.com/mainecruising/boat_projects

https://www.youtube.com/watch?v=z5RtZe9AW2E&index=9&list=UUoPqTkOluQsuu3RpGnxVwFw
 
Can't you accomplish your goal by simply having two batteries in parallel? We have dual batteries on all of our boats with a switch allowing both ON, both OFF and the choice of Bank-1 or Bank-2 only but all we ever use is both ON and both OFF.

It is our experience the batteries that stay equally charged have the longest combined health.
 
Originally Posted By: ArcticDriver
Can't you accomplish your goal by simply having two batteries in parallel? We have dual batteries on all of our boats with a switch allowing both ON, both OFF and the choice of Bank-1 or Bank-2 only but all we ever use is both ON and both OFF.

It is our experience the batteries that stay equally charged have the longest combined health.



This, isn't this how diesel trucks do it?
 
A pontoon boat is not in the same situation as a boat going 20 miles out into the ocean. But here is how a boat going into the ocean might wire things.

The best solution would be to alter the wiring to have the stereo and other non critical loads run off a house battery and have the engine run off a starting battery and install a "combiner" that combines them when the engine is running.
 
Originally Posted By: Sierra048
Originally Posted By: JHZR2
I like that switch because it looks like it lets you run on either or both batteries.

You'll need to be smart about charging, cycling and balancing batteries with the approach you propose.


That's just what I was thinking off the top of my head. I am open to suggestions. I am also limited with my options when not using the boat as far as keeping the batteries charged. There are no outlets for a battery charger at the covered marina we're at. So I'll probably have to remove one and take it home with me if there is any lengthy time away from the boat. Frustrating but that"s what we have to deal with.


That's a bit more of an issue. What's your plan for recharge, especially on the one used for hotel loads? I know you said take it home, but what's more important is how to make that convenuent. Hopefully your plan includes an easy access hatch and quick disconnects of some kind in order to bring them home and charge them right...
 
First of all, thanks to everyone who offered help and suggestions.

I have to be honest here, this has become more complicated than I wanted. I spent a good portion of the weekend reading and watching videos. I have seen some extremely exotic, and expensive set-ups, that are really impressive but for me I think overkill. Granted most of these set-up serviced a lot more elaborate situations than mine. As I mentioned in my opening post, I doubt that I'll ever really use any nav or courtesy lights, leaving the gauges and the radio as the only power draws after the engine is started. I did take the time to read all the links you posted. Thanks for linking the info. While adding VSRs and other automatic switching/isolating components might be nice, I just think that's making it more complicated and expensive. This is a lake pontoon boat. If I was talking about an ocean going vessel I would be more open to these types of things. So to simplify things please help me consider these two options:

1) If this is feasable, just buy a second battery, hook them up parallel, utilize the additional power for basically using the radio while anchored, while recharging both when running the engine.

2) Install this:



And accomplish the same goal as #1 with the additional requirement of having to turn the switch to the back-up battery if needed, or to dual charge them. From what I've read, this set up would protect one battery from being damaged should the other one go bad from being wired in parallel.

If I'm wrong please let me know. I'm no expert. I was actually amazed at how complicated battery technology and application can be.
 
With that simple setup you have to remember to switch to "both" when the engine is running so that both batteries get charged. Then remember to switch off of "both" while at anchor playing the stereo so that only one battery is running down. If you forget and leave the switch on "both" and run stuff connected to battery 2, battery 1 will also discharge and you may not be able to start the engine.

The isolator contains two big diodes. It would automatically direct the power from the alternator mostly into whichever battery is run down more, regardless of the switch setting. Having two diodes means that the voltage drop is balanced between the batteries.

Wiring an isolator requires bringing the alternator output out of the engine separately. This is very simple on inboard engines with an automotive type alternator, but with an outboard you will need to consult the manufacturer's recommendations.

The isolator setup is very useful since you could leave the switch on "1" for the whole cruise and start and stop the engine as much as you want, without thinking about batteries at all. If battery #2 runs down, the engine still starts from #1.

If you can't charge at the dock you should remove battery 2 from the boat and take it home to charge after each trip. Don't count on a few minutes of alternator charging to recover from a deep cycle of using the lights and stereo.
 
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Originally Posted By: mk378
With that simple setup you have to remember to switch to "both" when the engine is running so that both batteries get charged. Then remember to switch off of "both" while at anchor playing the stereo so that only one battery is running down. If you forget and leave the switch on "both" and run stuff connected to battery 2, battery 1 will also discharge and you may not be able to start the engine.

The isolator contains two big diodes. It would automatically direct the power from the alternator mostly into whichever battery is run down more, regardless of the switch setting. Having two diodes means that the voltage drop is balanced between the batteries.

Wiring an isolator requires bringing the alternator output out of the engine separately. This is very simple on inboard engines with an automotive type alternator, but with an outboard you will need to consult the manufacturer's recommendations.

The isolator setup is very useful since you could leave the switch on "1" for the whole cruise and start and stop the engine as much as you want, without thinking about batteries at all. If battery #2 runs down, the engine still starts from #1.

If you can't charge at the dock you should remove battery 2 from the boat and take it home to charge after each trip. Don't count on a few minutes of alternator charging to recover from a deep cycle of using the lights and stereo.


So your opinion is to take option #2 and add an isolator into the set-up? Does anyone have a diagram of how that would be wired? I do like the fact this set-up would decide on/manage the charging requirements between the two batteries automatically. I perused the Blue Sea website and I'll send them some questions on how best to move forward with their products and this set-up.
 
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