What is the easiest way to have dual batteries with an outboard, and have both batteries charge. I want to use one for a house, and one for starting, with the ability to combine them if I need to.

2 batteries and a battery switch like a quest switch.
It's pretty simple to wire up.

Ok lets say I use battery 2 for the house, how do I get it to charge, or will it charge automatically?

Should I get a OFF/1/Both/2 ?

Whatever position you have the switch at will charge that battery, select both will charge both.

OK thanks, the knuckleheads at the BIgBox marine don't know chit, they all had different answers..

I'm not sure if this is true or a wise tale,
But most people say never turn the switch once the motor is running

Here is the deal. You can switch between bateries while running only if your switch is make before break. The vast majority of switches are this. But I guess if you don't know then you should find out before you do it. Don't turn to off while you are runing. switch from 1 to both to 2, or vice versa. never to off. Never run on both.

To wire the boat for two batteries is quite simple. Wire ground of Batt 1 to ground of Batt 2. Run hot of batt 1 to switch. Run hot of batt 2 to switch. run hot off switch to outboard. run ground of batt 1 to outboard. run hot off switch to house. run ground off batt 2 to house. DONE. very easy. I did it in my last boat. I have done it in 4 friends boats. It is tooo easy. I just bought supplies to do it in my brand new boat.

I prefer the Blue Seas switch. I use #2 AWG wire for the long runs and #4 for the short runs. I have never done a boat bigger than 21'. I may use larger gauge for a bigger boat, I would have to do the calculations.

I have found the best prices at www.bestboatwire.com. About 1/4 the price of west marine.

Thanks I just ordered the rest of the stuff I need.

It'll work, but not ideal. The problem is that you'll have to run on "both" to charge the house battery. You could wire in a battery isolator and charge the house battery all the time the engine is running, without moving the switch and the isolator will prevent the house battery from draining into the engine battery, if something goes wrong.

What I have described is the standard for wiring dual batteries in small craft (23ft or less) with a single outboard. Typically what most people do is switch batteries durring the day. Some will run out on one, fish, then at some point, switch to two and use two for the run back. I usually alternate between main batteries each trip.

YOU DO NOT WANT TO RUN ON BOTH. If you have a problem battery that is not holding a chage, and you run on both, it will drain the good battery down to the charge of the bad battery. This is a fact. you will then be screwed with two bad bateries. Charge one, and then charge the other. If you are not able to start on one, then try the other. If you can't start on that one, then use both. That is the only time to use both.

You can wire like mike said with an isolator, but that is typically only used on large boats where there is a major drain on the house battery. For small craft it is not necessary.

What Mako Mike said is right on, even for a smaller boat....A battery isolator isn't big or too costly and will charge the battery that needs charging regardless of position.

What Zacs said is true about switching while running. If the switch makes before breaks it is ok. But you really want to avoid this at all cost. I know my switch states not to. If contact points move and things don't make and break good then there is a chance of blowing your isolation diodes in your alternator that convert AC to DC since all induced current is alternating.

Personally unlike what Zacs said I always run on both batteries. There is nothing wrong with this while running. The batteries are always getting charged etc. If your engine is off and fishing using juice well that is another issue,... that is what I do. And I do not have a battery isolator yet but someday will install one.

The only issue with battery isolators is sometimes you'll see a voltage drop accross the isolator.

For battery switches there is allot of choices anywhere from $25 and up. I prefer the more expensive bigger Cole-Hersey switches compared to the $25 Chinese Blue Seas stuff. Although for $25 is looks decent and small in size for a small boat. But I think you get what you pay for too.

Good luck with the install, it is easy to do yourself.

Well, i guess we could debate for hours, but if you are running on both, you are only charging to the voltage of your weakest battery. It is fine for 99% of the time when your batteries are fine, but if one goes and you don't know it you are screwed.

And blue seas is not junk. it is very good stuff. i don't know if it is made in china, but the stuff i have used is very high quality stuff. i have used their switch panels, fuse bars, and batery switches and they are all built real tough and it is all very high end. extra heavy duty made with good materials.

But, you have me thinking on the isolated batery setup. maybe it is a good idea. i am going to look into it, maybe it is the way to go, although I have never seen it on any of the small boats I have had or been on...

Zacs,

Not looking for any debate. Everyrone has opinions etc and I agree with most of what you say. If you say Blue Seas isn't junk I'll look closer at it. When I saw the low price of the switches I assume you get what you pay for.

You are right about leaving batteries on both all the time. They won't charge at the same rate etc. But I choose this way as to not to have to switch while running.

Not to get into this arguement, but again, somthing I get paid to do.

Wire in an isolator this way you know you are charging and it eliminates drain problems, do not switch when running. Blue seas is becoming the standard, cole hersee is in no way better at all. I have had way more cole hersee's replaced in my time then blue seas, they are just better made.
And seeing I manufacture my own instrument panels and compete with blue seas (although I do all custom panels), You can take my word that they are better. I use blue seas componenets and they actually put there own sticker on carling breakers, which are also the standard in breakers.

I know I am new here guys, but boats have been my life for 20 years, I own my own CNC laser and manufacture panels and design systems for many customers. I am not trying to argue or anything so don't take what I say the wrong way:)

Thanks for all the info everyone.

Scott I am running a 96 Johnson 90 on this boat, I am a little confused as to how to hook up an isolator, or even which one is a good one to get.

This one will work for you Jusst fine. You might be able to get it cheaper somewhere.

http://www.guestco.com/scpt/ProdPage.php?loadItem=2401A_Guest%20Recreational

Very simple to hook up, if you need me to , I can draw up a schematic of it.

You come from the altenator to the isolator, then to each battery

Being of a simpler mind:
Battery 1 = Odd days, Battery 2 = even days.

You really don't need to dedicate a battery to anything. Using/charging a single battery at a time seems to work just fine.
Unless you want to spend more money.

Being of a simpler mind:
Battery 1 = Odd days, Battery 2 = even days.

You really don't need to dedicate a battery to anything. Using/charging a single battery at a time seems to work just fine.
Unless you want to spend more money.


Hahaha, sure, that would work. Or he could just wire it up right and be done with it. An isolator cost little for the benifit. Imagine buying a brand new boat, and the salesman tells you " this is your even day battery, and this is your odd day battery":smash:

Just playing with ya dude:walk:

I put the switch on dual & it stays there ///been doing it for years // this season or next I,ll just buy two new batteries & trash the old ones .,.,

I put the switch on dual & it stays there ///been doing it for years // this season or next I,ll just buy two new batteries & trash the old ones .,.,

Ok, but do you have a sinlge or dual Diode altenator?

His is a single so you shouldn't Yes, you can, but you just shouldn't.

Go to bluesea.com and order thier FREE catalogue. It comes in a couple weeks and has each wiring system laid out and easy to understand. It gives all the diferent switch options. From what ive read bluesea is the standard now. I recommend the 5511e switch with the ACR. Its simple and easy to install, but each sysytem has its advantage and disadvantage. Check cables, if questionable, replace. These can be made by you cheaper and a better custom fit to your boat with the anchor crimper and the right connectors. Follow (ayba ??) rules and crimp then heat shrink.

i was goin to put duels in mine ,i wanted to put the batt. on the other side for even weight distrubution , went to the local marine store to get some cable $150. just for the cables , ouch ! i am going to have to rethink this move .

Try bestboatwire.com for wire and cable.

IIT is called ABYC or NMEA

ANd you can get connector with heat shrink already on them, it is easier.

Blue Oyster I bought some wire off of Bestboatwire.com They are way cheaper than anyone around here. They ship out from FLA on Monday's, and I got my stuff by thursday. You can borrow my lug crimper if you want.

I have already made up cables, installed a relay to control the fuse panel (Thanks for the help Scott), and put in the switch. I have rewired everything on my boat,and installed all of the new electronics, the only thing left to do is install the isolator. I have it, and the wire, just need some more time.

Blue Oyster I bought some wire off of Bestboatwire.com They are way cheaper than anyone around here. They ship out from FLA on Monday's, and I got my stuff by thursday. You can borrow my lug crimper if you want.

I have already made up cables, installed a relay to control the fuse panel (Thanks for the help Scott), and put in the switch. I have rewired everything on my boat,and installed all of the new electronics, the only thing left to do is install the isolator. I have it, and the wire, just need some more time.


Sweet sounds like your almost there! I just replaced half the deck in my boat today haha, so I am a little behind. I don't think I will even be installing the new panel I have been wanting to design this year. I can't complain, I got the boat motor and trailer for free:tooth:

This is why I have 3 batteries... really :hee:
I have one just for electronics and two for the engine.

I don't think they will all charge properly if the switch is not made to the battery you want to charge while running. Look at the amp meter when swithing. You will find the weak battery and can target that one if you like while running back home. I think it is OK to run on both if everything is functioning alright. Most alternaters are pretty powerful these days and can handle a dual or even triple set up.

Mine was a nightmare hookup with 3 Perko switches... I had to take it apart to figure out the logic but I ripped it down and it is much simpler now with just one switch.

- boss... for a nother 100$ u dont worrie about that problem ..the 1 batt. power sorese.always 2 batt. its worth it ...