Need help with wiring a second battery??

AngelC

Petty Officer 2nd Class
Joined
May 28, 2008
Messages
189
Hey Fellows,

I'm on to my second project for the winter. I'm adding a second battery. I have the blue top optima that I'm going to add. I bought the selector switch. Just need help or an exact diagram for wiring up the second battery. These are some pics of what I am working with.

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070008.jpg

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070010.jpg

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070015.jpg

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070014.jpg

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070012.jpg

As you can see I will add the battery #2 the Optima on the opposite corner on a battery tray with a strap similar to battery #1. The battery that's in there now is the primary to start up with but it also runs the lights and stereo and gages etc. I would like to run my stereo system strickly off battery #2 the Optima. My alternator is a 75 amp with an internal transistorized voltage regulator. I am aware that I will not be able to sustain a substantial charge for both batteries and I'm fine with that I will primarily leave it on battery one so I will always have that battery charged when I'm underway. I will charge battery #2 at home with my charger. Battery #2 will only be used for my stereo system. Can someone explain what I will need as far as cables, what gauge? and how I will wire this up for what I want to use this set-up for??

Your help once again would be appreciated,

Thank you,
:confused:
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,562
Re: Need help with wiring a second battery??

That's a great primer on adding a second battery. There is also a brief wiring guide on the Blue Seas switch package. You are adding a "house" battery, so that you will have separate "house" and "starting" batteries, which can be tied together with the switch for charging or emergency (start battery is flat) starting. As an electronics engineer and boat instrument installer, I would add a few details:

1. Use only 100% tinned, marine-grade wire, and proper crimp connectors, covered with marine-grade, adhesive-lined shrink tubing, such as Ancor brand marine wiring. The wire sizing for your setup should be at least 4 AWG (or heavier) -- 2 (or 0) AWG is better yet.

2. The (-) ground side will be common, so it doesn't go anywhere near the switch. You can run a main ground between batteries, or a ground wire from each battery to the ground bus, and that takes care of half the circuit.

3. Put your accessory wires onto a common bus bar (you will want two -- one for ground, and the other for (+), and then run only one heavy lead from each bus to the battery banks. Cleans up the installation a lot, and makes any future installations or troubleshooting much easier.

4. Run the motor ground lead to the "start" battery (your existing "battery 1"), and run the motor (+) lead to the "common" pole at the switch. Run pole 1 of the switch to battery 1, and pole 2 of the switch to battery 2. Run the the accessory bus leads to the "house" battery (your new "battery 2").

With this arrangement, your motor can go to either 1, 2, or 1+2. The switch will connect the batteries in parallel when switched to "1+2". This way, the accessories always see "house" battery 2, but can also see "start" battery 1 if the switch is set to "1+2".

At 75 amps, you have enough charging capacity to top up both batteries when underway and the switch is set to "1+2". Also, if your start battery is flat for some reason, you can switch to "1+2" so the motor sees both batteries for emergency starting.

Just remember two things:

1. If you leave the switch in "1+2" and drain the batteries, everything is flat. So only use "1+2" for charging or emergencies.

2. With this style of switch, do not set the switch to 0 (off) while the motor is running, ever, or you run the risk of cooking the diodes in the alternator. As an alternative, Blue Seas makes a similar (but more expensive) switch that has field wire connections, that tolerates accidentally setting the switch to off when running.

HTH.
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Need help with wiring a second battery??

Courtsey of Silvertip.

StandardBatterySwitchWiring.jpg
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Need help with wiring a second battery??

So here is a question for you! If you plan to leave the switch on BAT #1 and plan to charge BAT #2 at the dock, why on earth would you bother installing the switch? Leaving the switch on BAT #1 would be no different than the situation you have now without the switch. You could simply add the second battery and connect your stereo to it. You don't need the switch for that.

But since you have the switch, add it and use it as it is intended to be used. Everything on the boat, except for the bilge pump should be wired to the COM terminal on the switch. Your alternator will handle both batteries since BAT #1 (the start battery) should never get deeply discharged. If anything, leave the switch on BOTH and switch to BAT #2 when anchored. On that setting, everything will operate from BAT #2 leaving BAT #1 fresh for a restart. When ready to go, switch back to BAT #1 or BOTH and go! If you switch to BAT #1 to start, switch to BOTH after startup. Both batteries will charge. If either battery is discharged, after starting, switch to the discharged battery to quickly charge it while under way.
 

AngelC

Petty Officer 2nd Class
Joined
May 28, 2008
Messages
189
Re: Need help with wiring a second battery??

Silvertip,
I was just told that battery #2 would not get a good charge. I did get the switch to try though and if that did'nt work then I would charge on dock. Fellows thanks for all the tips and diagrams that was what I exactly needed. Tashasdaddy that diagram could not be any clearer and easy to comprehend, Perfect!! Thank you!! This is where I'm at so far.I am done for the weekend I've installed the battery in the conpartment and just trying to figure out where I want to mount the swithch and then I will begin the wiring process.

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070019.jpg

http://i480.photobucket.com/albums/rr168/AZcontreras1/P1070024.jpg

I will probably get started on the wiring in the next couple of weeks.

Thanks again guys for all your help!!

Angel:)
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Need help with wiring a second battery??

thank Silvertip for the Diagram, i borrowed it from him. TD.
 

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,746
Re: Need help with wiring a second battery??

Keep this in mind for in the future, the switch on my boat when I bought it was in the 1&2 position, all good for 1st trip out, then disaster, + cable fried because it was chaffed it had rubbed through to ground, fuse saved my boat.

I cleaned the whole mess up and re-routed cables neatly with the use of buss bars.
Also during this whole chain of events is when I found the #2 battery had a dead cell and was absolute junk, with the switch set on 1&2 the cooked battery didn't show up maybe it cooked when the pos. cable shorted out I don't know, from then on I practice alternating the batterys.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Need help with wiring a second battery??

AngleC -- think about this. You alternator does a good job of charging the existing start battery BAT 1) does it not? When you add the switch you will have the option of charging BAT 1, BAT 2 or BOTH. As I pointed out, merely switching to BAT 2 when you are under way will allow full alternator output to go to BAT 2. If the alternator keeps BAT 1 charged it will keep BAT 2 charged. And whoever told you batteries in parallel (BOTH) will not charge evenly is mistaken. There are a gazillion dual (parallel) battery vehicles running from a single alternator and they do just fine.
 

AngelC

Petty Officer 2nd Class
Joined
May 28, 2008
Messages
189
Re: Need help with wiring a second battery??

Hey Guys,

How's it going out their?
I have a question about my battery cables. Do I have to buy marine grade cable? or can I get by purchasing 4awg from an Auto parts store? My local Napa Auto Parts sells the cable by the foot and puts the eyelids on for me for about $1.99 a ft. verses West Marine or Boatersworld that is WAY MORE expensive and alomost identical besides the coating on the wire I presume. What do you fellows think I just need two cuts of 4ft of red and one cut of 6ft. black for a ground to hook up my battery selector switch. Can I get by with using this cable?? Any input as always very much appreciated.

Thank you
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,562
Re: Need help with wiring a second battery??

You need less than 20 feet of wire altogether. So put the cost in perspective.

Use only 100% tinned, marine-grade wire, and proper crimp connectors, covered with marine-grade, adhesive-lined shrink tubing, such as Ancor brand marine wiring. The wire sizing for your setup should be at least 4 AWG (or heavier) -- 2 (or 0) AWG is better yet.

Yes, car wire will work -- for a while. But then so will a car battery. Neither is recommended for the marine environment -- especially in salt.
 
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