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Author Topic:   Blue Sea Add a Battery - 7650
retired posted 04-21-2012 12:26 AM ET (US)   Profile for retired  
I will be installing a Blue Sea Add a Battery 7650 to my [1998 Boston Whaler Conquest 21] with a Mercury 200-HP EFI outboard motor. [The boat] is equipped with two batteries and a Perko OFF-1-BOTH-2 battery switch, as shown here.

What size wire and fuses do I need between the batteries and the [automatic combiner relay or] ACR?

What is better to use: a breaker or a fuse? I am not quite sure of the charging [current] of the 200 Mercury, but I believe that it is 40-Amperes.

The new 5511E switch will be replacing the Perko switch and the [automatic combiner relay] will be easily within two-feet from the switch. I will run a 16-AWG wire fused by 10-Ampere fuse between the ACR and the common bus. Feel free to add any other comments or suggestions.


ericflys posted 04-21-2012 06:38 AM ET (US)     Profile for ericflys  Send Email to ericflys     
I'm sure you'll get some conflicting views here, as the wiring schematic shows fuses and a chart for selecting the size.

After having talked to the factory techs, I chose not to run a fuse or breaker between my batteries and the this ACR. There is some built in protection in the ACR, but it will not be usable after protecting your boat from a short, much like a fuse. but since the difference in cost is between the ACR and a quality circuit breaker isn't that big and the wiring run is very short with very little chance of a short ever occurring, I don't think you need one there. Of course, all loads connected to your house buss must be fuse protected to protect both them and the ACR.

I assume by "common" bus you mean house bus. You must have very small loads there if you are running 16ga wire and a 10 amp fuse.

Also of note, the ground wire to the ACR should have a fuse in it. For this I'm running an inline ATO fuse.

jimh posted 04-21-2012 09:34 AM ET (US)     Profile for jimh  Send Email to jimh     
I suggest you follow the manufacturer's suggested practices for installation of the new primary power switch and the automatic combiner relay.

I don't understand your narrative about your intended installation where you say, "I will run a 16-AWG wire fused by 10-Ampere fuse between the ACR and the common bus."

If you are referring to the connection of the ACR to the two batteries, the wire size should be larger than 16-AWG. See the manufacturer's recommendation. I suspect they recommend a much larger conductor.

jharrell posted 04-21-2012 12:03 PM ET (US)     Profile for jharrell    
The ACR require a small amount of power to operate, it draws this power from the positive battery terminals but requires a small ground wire to complete the circuit, only large enough to handle the minimal current draw of the ACR, not the charging current. This is the 16 gauge wire and 10 amp fuse being referred to.

This ground is the primary path for any possible short for the high current positive battery leads to ground through the ACR itself. Therefore the 10 amp fuse on the ground is highly recommend to break the circuit should the ACR itself have an internal failure causing short to ground.

Blue sea shows high current circuit breakers or fuses large enough to handle charging current flowing between the positive battery leads on the ACR and the batteries themselves. As ericflys mentioned if you have any knowledge of the nature of electrical circuits and discuss the matter with Blue Sea support you will realize the high current fuses are not necessary if the positive wire from the batteries to the ACR are relatively short and do not pass through or near possible ground points in the boat. It would be akin to putting high current fuses on the positive leads for the main power switch. They will buy you very slightly more assurance of ground short protection but at a high cost. After all, all power wires in a boat could be made safer by putting the proper size fuse on each end, this is simply not done because the cost is prohibitive. Blue sea is simply shows worst case installation senario since they do not know whether the boat is metal or how far or long and what conduits the battery leads go through.

Incidentally the BEP 710 voltage sensitive relay and the coinciding BEP battery switch clusters that incorporate the 710 which are the primary alternative to the Blue Sea offerings, recommend absolutely no fusing even on the ground lead. BEP seems to have no concern for possible short to ground situations in thier instructions, while Blue Sea seems extremely conservative with theirs.

I choose the middle ground, protecting the primary short to ground through the ACR with a 10 amp inline fuse, but leaving off the high current protection on the positive leads.

You can see pictures of my Blue Sea ACR installation on my Montauk here: WhalerProject?authkey=Gv1sRgCOHiqYL_38ejFw&feat=directlink

jharrell posted 04-21-2012 12:26 PM ET (US)     Profile for jharrell    
I used 4 gauge battery cable to connect the positive leads on the ACR to the switch, roughly 12" each.

This should easily handle the maximum 125 amps the ACR is rated for. That amount of current would only occur if one battery where extremely low while the othe fully charged, that would only occur for a short time as the fully charged batteries voltage would drop off quickly disengaging the ACR.

retired posted 04-29-2012 12:07 AM ET (US)     Profile for retired    
jharrell--I agree with you in regard to not using the fuses between the ACR and the batteries. From the picture that you posted, your wiring is different from what the Blue Sea literature shows.

[This pictorial wiring diagram shows] how I am thinking of doing the wiring. It is basically what comes from the Blue Sea literature, but I have eliminated the two fuses and will also be using 4 gauge cables between the batteries and the ACR.

ericflys posted 04-29-2012 12:18 AM ET (US)     Profile for ericflys  Send Email to ericflys     
There is another option, that I'm using on my boat. You can wire the ACR in-line between the batteries and the switch. Essentially the wires from the batteries to the ACR and then to the switch. It accomplishes the exact same thing except there is less wiring, making the install cleaner in my application.
retired posted 04-29-2012 02:58 AM ET (US)     Profile for retired    
You mean like [pictorial wiring diagram].
jimh posted 04-29-2012 08:56 AM ET (US)     Profile for jimh  Send Email to jimh     
If the installation of the ACR omits all the ancillary components that Blue Sea Systems specifies in their installation instructions--as suggested by the links to very simple wiring diagrams given above--the ACR circuit become quite simplified. The ACR installation just adds three wires and one fuse.

If I were to get an ACR, I would use the Blue Sea Systems device PN7610 SI ACR Automatic Charging Relay with Starting Isolation, and I would install it as recommended in their literature, although I would probably omit those two very expensive high-current fuses in the main battery leads, for the reasons mentioned already in this discussion. I am certain that 99 of 100 installations omit those expensive high-current fuses.

The PN7610 device provides for a special feature called starting isolation that helps to prevent engine starting voltage sags from affecting the second battery, usually the HOUSE battery. This is an important feature in my opinion, as it will help avoid problems with electronic devices rebooting when the engine is started due to voltage sag. The added components needed to implement the starting isolation feature are simple and inexpensive, and I think their cost and installation are small compared to the benefit they provide. I would probably add the LED indicator circuit, too. Heck, a fellow can't have too many LED indicators, can he?

jimh posted 04-29-2012 09:04 AM ET (US)     Profile for jimh  Send Email to jimh     
In power distribution wiring that has been done to a high standard, you will not find multiple conductors secured under a single terminal post. Bus bars will be used instead. Although fastening more than one conductor under a terminal post is not recommended, it is a very common practice in small boat electrical installations.
ericflys posted 04-29-2012 12:44 PM ET (US)     Profile for ericflys  Send Email to ericflys     
Retired, that is how my ACR is connected. I do have two terminals on one post with setup. I agree with Jimh, and try to avoid this whenever possible. However, when installing an ACR is almost impossible to avoid having two terminals on either the battery posts or the ACR posts. It would only be possible if your batter had two posts, which mine do not.

There is an LED on the ACR, but I can only see it when I look inside my console as that is where my ACR is located. I decided to also wire in the remote LED as well. It makes me feel good looking down at my panel and seeing it illuminated.

jharrell posted 04-29-2012 02:22 PM ET (US)     Profile for jharrell    
From the picture that you posted, your wiring is different from what the Blue Sea literature shows.

Yes although electrically the circuit is identical, I used the switches battery side post to connect the ACR to rather than the batteries positive posts as shown in the literature from Blue Sea.

This allowed much shorter leads to the ACR, rather than running them all the way back down to the battery, which I already had 2 gauge wire run to the switch for. Blue Sea's 5511e Switch has long 3/8 studs (The same size as on a typical battery) with plenty of room to safely accommodate the double wire rings.

My inspiration came from BEP's 716 cluster which factory wiring has the ACR/VSR tied to the same studs on the switch as batteries. Again BEP has no fusing and much smaller wiring between switch and VSR (8 gauge a believe) along with open uninsulated tie bars, this make me pretty confident my setup with ground wire fuse protection and 4 gauge non fused ACR leads are much more than adequate and safe. You can see the BEP 716' factory wiring here:

jharrell posted 04-29-2012 02:34 PM ET (US)     Profile for jharrell    
I did contemplate adding a positive bus bar in addition to the negative one I added. However after examining the Blue Sea Switch and ACR and seeing that both had long 3/8 studs I came to the conclusion a positive bus bar would have complicated things unnecessarily as well as adding significant cost.

I have not yet hooked up the start isolation or remote charge led leads on the Blue Sea ACR. I had intended to but have simply not had time. I have noticed no issues with my electronics so far without start isolation, although I had no distinct house circuit before and never seemed to have an issue either. The charge indicator LED on the dash would be a convenient way to let me know both my engine and built in charger are functioning properly both under way and in the garage without having to look into the console.

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