How to hook 2nd batt up to alt?

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LAC_STS

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I installed a 2nd battery. The spot and the battery switch was alrady there just had to drop in the battery

After using it I found out that it is not being charged by the alt. How do I hook it up so it charges the 2nd battery also?

I have a 5.7 OMC with the 3 wire alt.

Heres a pic of the back of the alt. I assume its the thicker orange wire that charges the battery right? If so, how should I hook this wire up to the battery?

Is it safe to just splice into the wire and run one to the second batt?
 

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L

LAC_STS

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Re: How to hook 2nd batt up to alt?

Ummm

I have a batt selector switch. When j was running on the second batt it died. So it's bit being charged.
 
QC

QC

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Re: How to hook 2nd batt up to alt?

LAC_STS said:
When j was running on the second batt it died. So it's bit being charged.
Click to expand...
How do you conclude that from this? I am moving this to electronics, but if you have a selector switch you should not have to touch the alternator, You wire the second battery to the selector switch. Done.
 
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LAC_STS

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Re: How to hook 2nd batt up to alt?

So you just hook the 1 pos and 1 neg battery cables up to the 2nd batt and it should charge?

If so then something is wrong? I was thinking that it should have a wire from the alt going to it.
 
Eric 3.7LX Alpha 1

Eric 3.7LX Alpha 1

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Re: How to hook 2nd batt up to alt?

Did you look on the back of the switch ? there are 3-terminals,
Batt-1 Positive
Batt-2 Positive
common terminal- to starter on engine

Battery negatives go to ground, you can run the new negative to the existing battery negative terminal or where it attaches to the block.

The alternator will charge either battery or both depending on where the switch is selected.

The switch might possibly be NG, Use a multi meter set on continuity,(beeps when wires touched)
Disconnect all wires and should have continuity between common terminal and whatever battery terminal is selected.
 
Silvertip

Silvertip

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Re: How to hook 2nd batt up to alt?

You do it this way: Yes -- this diagram shows an outboard. But notice that the POSITIVE battery cable from the engine goes to the switch. On your boat you do not see a charging wire from the alternator to the battery do you? That's because the alternator output generally goes to the starter solenoid where it mates up with the large positive battery cable which goes to the engine. Therefore you do not get near the alternator when you add a switch and second battery. To charge both batteries at the same time you set the switch to BOTH. Both batteries will then be powering the electrical system as well. When set the BAT 1 ONLY battery #1 is charged and ONLY BAT 1 runs the electrical system. Same for BAT 2 setting. The +12 volt feed for the boat harness (not the engine harness) should be moved from the start battery to the COM terminal as well.

StandardBatterySwitchWiring.jpg
 
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LAC_STS

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Re: How to hook 2nd batt up to alt?

Ok thanks everyone.

Ill have to check all this out when I go to the boat later on today.

What I did was: The boat has always run off of 1 batt, #1. I installed a 2nd batt and when I did I put the switch to #2 and ran the boat for a little while.

The engine later died and I lost all electrical power. I checked and the switch was set to #2. I changed it to #1 and the engine started right up. checked the #2 batt and it was dead.


I will check later and see if everything is wierd right.


thanks again
 
Silvertip

Silvertip

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Re: How to hook 2nd batt up to alt?

Just to make sure you understand -- the red and black wires coming from the engine are the large battery cables. These are not wires you run from the alternator.
 
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LAC_STS

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Re: How to hook 2nd batt up to alt?

Silvertip said:
Just to make sure you understand -- the red and black wires coming from the engine are the large battery cables. These are not wires you run from the alternator.
Click to expand...

Correct
 
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LAC_STS

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Re: How to hook 2nd batt up to alt?

Ok I checked it out yes and the batt switch is working. I removed the switch from the boat and checked everything. I got 15V on 1 if I set it to 1, 15 on 2 if I set it to 2 and 15 to both if I set it to both.


So maybe my problem lises with the second battery I installed. I dunno Im gonna run it on different ones and see what happens.
 
Silvertip

Silvertip

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Re: How to hook 2nd batt up to alt?

I am very curious how one gets 15 volts out a 12 volt battery???????
 
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LAC_STS

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Re: How to hook 2nd batt up to alt?

Because the engine was running. Alt puts out 15V.

Hence me question about whether the second battery was getting charged. I knew the second batt worked when switched to it but didn't think it was charging.

Now i know it is charging but batt might be bad.
 
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