Re: Multiple Battery Wiring Diagrams (II)

[stevecut]

Re: Multiple Battery Wiring Diagrams (II)

how do you ground two batteries

 

[Silvertip]

Re: Re: Multiple Battery Wiring Diagrams (II)

Ground them to what? In a 12V parallel system you connect negative on BAT 1 to negative on BAT 2. Positive on BAT 1 to positive on BAT 2. The positive and negative leads to the loads can then be connected to the positive and negative terminals on either battery. You usually have to fabricate the interconnecting cables.

 

[Reel Poor]

Re: Multiple Battery Wiring Diagrams (II)

Re: Multiple Battery Wiring Diagrams (II)

how do you ground two batteries

Send them to their rooms? Just kidding.

Seriously;
Is this on a inboard outboard, or an outboard set up?

Here is a diagram of the proper way to wire a dual battery set up. Ground each battery to the engine block on seprate bolts or studs. Hooking batteries directly together is not as ideal as seperate connections.

 

[ricksrster]

Re: Re: Multiple Battery Wiring Diagrams (II)

One thing to add to Reel Poor's answer. The switch should be make before break. This protects your motor's charging system.

 

[philobite]

Re: Re: Multiple Battery Wiring Diagrams (II)

If I may tack on a question:

I have an '87 'rude 48SPL and was wondering if/how I could implement Reel Poor's wiring diagram since I don't have an alternator per-se. I just have the + and ground cables going to the starter battery. In other words, how would I hook up the isolator to charge 2 batts, and the selector switch considering that I have an outboard?

 

[ricksrster]

Re: Re: Multiple Battery Wiring Diagrams (II)

Use the positive post on the regulator.

 

[Silvertip]

Re: Re: Multiple Battery Wiring Diagrams (II)

Look on the starter solenoid and you'll see a smaller wire connected to the same post that the large red positive battery cable is connected to. That smaller wire is the charging line. It charges the battery through the POS battery cable. That smaller wire gets disconnected and feeds the COM terminal on the isolator or switch. A new wire from the isolator or switch goes back to the solenoid where the charging wire was attached.

 

[Silvertip]

Re: Re: Multiple Battery Wiring Diagrams (II)

Almost forgot. I'm not sure but I think the 48 SPL had a relatively low alternator output. Some engines in the 40-50 HP range (your 48 is an economy 50) had a 12 Amp alternator while some may have been as low as 6A. Either way, if you are using the seond battery for a trolling motor, you may want to rethink this plan as the engine would need to run wide open for hours to top off the second battery. If the seond battery is simply backup, then your plan is ok.

 

[philobite]

Re: Re: Multiple Battery Wiring Diagrams (II)

Silvertip and Rickstster,

Thanks for the very helpful responses. I understand now what I need to do, and what the issues are. The trolling batt is only used very occasionally and in those cases I can recharge at home. What I want to do is have the troll batt as both a backup "just in case" when I'm on the ocean, and to hook up my marine radio, gas gauge, fish finder, and 2 downriggers and "black box" to it and have the motor keep a charge against that light current drain.

At present the boat has 4 batts (EverStart), 1) Engine (only one hooked up to that circuit), 2) Downriggers, 3) Troll, 4) Marine radio, gas gauge, fish finder, black box. Batts 2 thru 4 have to be recharged manually at home. For weight, space and complexity reasons I want to get it to 2 batts.