Mini Add-a-Battery (Blue Sea 7649) Wiring Help

sdman67

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1976 Mercruiser 233 I/O in a 1977 Sea Ray 220 Hardtop O/N
The Blue Sea wiring diagram is not very detailed for obvious every application is different reasons. Can anyone mark-up the attached Seloc wiring diagram or download one from their own project? I also attached the Blue Sea diagram for reference.

I've spent the day reading various posts regarding this product and have found a lot of people claiming the Blue Sea 7649 should only be used on outboards, but it's rated for 65A and my alternator is only 42A...I'm assuming this will work fine...any advice to the contrary?

Thanks

Frank V
 

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sdman67

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Thanks for the reference to the post, but if anything it convinced me that the Mini will work just fine. The cranking amps are going through the switch and I measured my starter's draw at around 250 amps which is well within the specs bruce58 posted from his Blue Sea research.
 

bruceb58

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I use a mini on one of my boats(pontoon with outboard) and the regular one on the other. Personally, I would go with larger version for a V8 engine even though the switch's max current specs are pretty close. As far as the ACR goes, you are correct that the ACR specs are fine with your alternator. Think there is a chance you would ever put in a larger alternator?

Do you have a size restriction which makes you want to pick the mini? Are you finding large price differences to make you want to go with the mini?

The prices between the two are pretty similar. Only reason I used the mini on my outboard application was how I was mounting it.
 
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sdman67

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Thanks for the reply bruceb58. I don't foresee needing a larger alternator in the future, I've replaced every fixture or every bulb with LEDs and the only other things I run are a VHF radio and a small livewell pump. If I turn everything on at once I suspect I may be drawing 25 amps. I looked into returning this mini in exchange for the bigger switch assembly today, but my wife got this thing with a 50% off (sorry we screwed up your last order) coupon and I would have to repay the discount and pay full price for the other so we're going with what we got for now.

As for the wiring...it dawned on me at 3AM that I don't have any problems with the big NAPA dual purpose ever even thinking of letting me down, I just want that piece of mind as we venture further and further away from shore. So I've decide instead of isolating anything I currently run to a house battery, I would just keep everything as is and add a start battery with the switch to combine for a jump start if needed. My wiring diagram is attached if anyone sees a problem with this please let me know.

Thanks to everyone who offered advice...
 

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bruceb58

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For what you are trying to do, you should really get a 1/2/both switch and not the one that comes with the "add a battery". The problem is that if your start battery was truly completely dead, you would want that battery completely out of the picture and not to combine it with the "good" one.

That switch that comes with the kit is meant for separate house loads. My Wellcraft is the same situation you have and I have the 1/2/Both switch.
 

mjf55

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Bruce58, for the 1/2/both switches, I ASSUME that you would want a make before break type of switch, but how about AFD (Alternator Field Disconnect)? Is that a useful feature?
 

sdman67

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I'm looking at the Blue Sea 9002e which will handle what I need to do, but do I still use the ACR?
 

bruceb58

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Yes, the Blue Sea 9002e is what you would want. Yes, you still want to have an ACR.

Most switches these days including the Blue Sea are "make before break" switches. Just don't go through the off position when the engine is running.

AFD is not needed with make before break.
 

dingbat

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For what you are trying to do, you should really get a 1/2/both switch and not the one that comes with the "add a battery". The problem is that if your start battery was truly completely dead, you would want that battery completely out of the picture and not to combine it with the "good" one.

Having been in the situation you describe, I would rather use the on/off/both switch and pull the cable off the dead battery than risk problems with both batteries because I forget to manipulate the switch properly.

I guess it boils down to what problem are you trying to solve. In my case, a dead starting battery is far less likely than me failing to manipulate the switch properly
 

bruceb58

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Having been in the situation you describe, I would rather use the on/off/both switch and pull the cable off the dead battery than risk problems with both batteries because I forget to manipulate the switch properly.
Did you look his diagram? He is not using the load side of the switch for house loads.
 

dingbat

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Did you look his diagram? He is not using the load side of the switch for house loads.

I see that....

Scratching my head as to why the short cut. In most cases, isolating the house load is simply moving a couple of wires from the positive terminal on the battery to the switch. I think I had three wires. The main to the power distribution panel and the fore and aft bilge pump connections
 

bruceb58

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I see that....

Scratching my head as to why the short cut. In most cases, isolating the house load is simply moving a couple of wires from the positive terminal on the battery to the switch. I think I had three wires. The main to the power distribution panel and the fore and aft bilge pump connections
With an I/O it's a little more involved. Problem is the large gauge wire that feeds the console fuse panel is a mixture of engine and accessory loads and those would all need to be on separate circuits.
 
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