Installing dual batteries

[hog wild]

I have a 21' Northriver Scout with just a single battery and am interested in installing a second one with a switch is this a task I should have done by a shop or something that can be done by myself?

[NewMoon]

Fairly easy, but needs to be done carefully.

Find secure mounting positions for batteries and switch, ideally protected from the elements. It's good to keep wire runs between batteries, switch, and engine short, because longer wires have more resistance and diminish voltage.

Once you have determined mounting positions, measure wire lengths. Don't underestimate the length of wire you'll need and cut too short. Battery cables don't make sharp bends well. Make sure the wire is top quality tinned wire, and don't scrimp on the gauge (longer runs need thicker wire).

Battery/switch connections need to be best possible quality also, done either with a heavy duty crimper, or soldered (only if you know how to solder big wire lugs correctly). The lugs must be exactly the right size for the wire gauge you're using. Use heat shrink tubing with hot glue inside to seal and protect the connection between wire and lug. You'll need a heat gun to shrink it onto the wire. Don't forget to slide the piece of heat shrink tubing onto the wire before you attach the lug.

Some wire suppliers will cut to size and crimp the lugs on for you, but of course you must be sure your measurements are correct. It's more of a sure thing to cut the wires only after you've put them in position and are sure you have the lengths right.

Assuming a 1-Both-2-Off switch: You want the negative posts of both batteries connected to the common negative wiring on the boat. A good way to do this is to run the negative cables from the batteries to a bus bar, to which all the boat's negative circuits are connected. The positive post of one battery goes to the #1 connection on the switch, the other battery's positive post to #2 on the switch. Connect the common positive on the switch to the positive boat wiring - again using a bus bar is good.

With this setup you can have either battery supplying juice, and being charged when the engine runs. Or if you turn the switch to Both, both batteries are connected. You can switch between battery 1, Both, and battery 2 with the engine running, but do not turn the switch to Off with engine running.

One good way to make the most effective use of battery weight is to have a starting oriented (cranking amps) battery on one side (this one can be relatively small and light), and a house or deep cycle (amp hours oriented) battery on the other side. Run with the house battery connected almost all of the time. Switch to the starting battery when you need to crank the engine, run that way long enough (10-20 minutes?) to thoroughly recharge the starting battery, then switch back to the house battery and leave it there until the next startup.

If you've been running during the day, and shut down the main engine for a while, then need to restart it, you may even be able to start from the house battery. If it won't crank, switch to the start battery as above.

[hog wild]

Thanks New Moon for the detailed help. I will take my time and see if I can do this from the info. you've given. Thanks again

[Riverteeth]

Another thought-- you can go the standard "perko" style switch. But I would reccomend something different: ACR switch. Can't remeber exactly what the acronym stands for, but what it does is charge both batteries while in use; and you can pull juice from both batteries in an emergency if you need to. There are a couple of other advantages over the standard switch, but I can't recall them all right now.

Talk to Robert at Marine Technical Experts on this website (he has his own forum/thread at the top of this section, next to "Boat Doc"). Robert is very good and can help you with this.

Chris

[fishkisser]

Make sure you mount your selector switch in a location that is out of the spray/ weather ...
Use the proper wire size for length of run and amperage ...
Make sure your switch will handle the amperage need to crank over your motor ...
No more than 3 terminals on a lug ...
Use dielectric grease for all mechanical connections or paint them closed with liquid electrical tape
I don't like to seal them completely as you cannot visually inspect them so I use dielectric silicone grease

heres some info ...

http://shop.genuinedealz.com/Marine%...ttery%20Cable/
http://www.ehow.com/how_5797879_conn...ries-boat.html
http://continuouswave.com/whaler/ref...alBattery.html

[Duckdog98604]

Post a pic when Your done.. I have one and would like to do the same...

[Seon]

You can wire your batteries like this



Or use an isolator and wire it like this

[Tide Change]

Originally Posted by Riverteeth

But I would reccomend something different: ACR switch. Can't remeber exactly what the acronym stands for, but what it does is charge both batteries while in use; and you can pull juice from both batteries in an emergency if you need to.

Chris

Chris brings up a good point. Google "ACR" (automatic charging relay), or look up Blue Sea Systems for more information. Just as easy to install as a simple Perko switch, but gives you added benefits.

[FanOFishin]

I installed dual blue top Optimax batteries in my boat and completely did the boat wiring following pretty much the exact steps outlined by Newmoon. It took a little time but I'm glad I did it and have been very happy with the setup. I installed a regular Perko switch but based on this thread need to look into the ACR type switch referenced. I'm sure you'll be happy with the set up once you're done .

[jomp1981]

Wouldn't recommend the isolator. I've had them go bad and then you're moving terminals around to get batteries to charge. Not fun on the water. Also if isolator goes bad under heavy load it could cause a voltage spike(due to regulator not seeing battery voltage for a referance point) and smoke the voltage regulator. I'm sure some people haven't had a problem, just my opinion.

[RiverJohn]

Originally Posted by Seon

You can wire your batteries like this



Or use an isolator and wire it like this

My NR Seahawk was originally ordered as dual battery and is exactly like the top diagram.

I have since added a Guest on board charger. Very pleased.

[sinkerhead]

I'd give another vote for the ACR, or in my case, its a VSR (Voltage Sensitive Relay).

I had a Perko switch and was concerned with having to lift the motor cover to change the position all the time, and forgetting too sometimes. The number one concern I had was that since all my positives were connected together, my accessories would always get reset whenever I started my main motor. I also had way to many wires coming off the output of the Perko (Bilge pump, TR1, washdown pump, alternator, cabin power, starter, etc).

I bought and installed a BEP cluster with VSR (about $150) and installed a covered bus bar (another $25). This system keeps the start and house battery circuits separate, except when running the main motor and the start battery gets fully charged, it then connects and charges both batteries. When I turn off the main motor, the battery circuits separate again (after the voltage drops a bit). It was an easy swap with the Perko that was there, and now when I start the main, the expensive accessories (FF/GPS, TR-1) don't reset. The main marketing point of the VSR/ACR is that it always ensures that the start battery is fully charged.

Here is the before picture with the Perko.



After installing the BEP cluster and +bus bar. Still need to do some tidying up !

[Jay in Kitsap]

I did the BEP VSR with the one switch that does 1-both-2-off. My house battery is up near the helm. I did a variation of what Seon showed but I added a feed with Blue Sea switch/CB from battery 2 to my fuse panel.

I can turn off the power to the engine at the battery switch or leave it on battery 1. When the engine is running, battery 1 charges, then automatically charges 2 but cuts out when the voltage drops when off or starting. The Blue Sea switch turns off all other power except for the bilge pump.

Greg's Marine Wire Supply http://gregsmarinewiresupply.com/ was where I bought all of my wire for my project. I used some old house wire to lay out my wires so I could get the bends etc all right, cut it to length, pulled it back out and measured the needed length. I ordered the cables with the lugs installed. No waste and just the right length. Greg's service is excellent along with very good prices.

jay

[sinkerhead]

Originally Posted by sinkerhead

Somebody has been tinkering with the pictures I posted. Oh well

[jfa686]

Originally Posted by RiverJohn

I have since added a Guest on board charger. Very pleased.

x2....if your going to a 2 battery system throw on a dual bank charger and you will never worry about state of charge again!!!! the confidence and piece of mind knowing both batteries are always topped off is awesome