Electrical, ACR (Automatic Charging Relay), Part 1: Installation of Positive Cables

The ACR with its positive cables installed
An ACR, or Automatic Charging Relay, is a useful piece of equipment on a cruising sailboat. It enables you to charge two separate battery banks at the same time from a single charger. Knowing that I wanted to have as much battery power as possible on Oystercatcher, my Ericson 25, I decided that the incorporation of an ACR into my plans for a complete rewiring of the boat was essential. If you've read my article on the DC main circuit, then you'll know that I decided to affix a number of components of the DC main circuit to a backplane - a piece of Starboard, or marine grade HDPE (high-density polyethylene) - and that I fastened this backplane to the bulkhead on the portside of the lazarette, directly beneath some of the other components of the DC main circuit located in the portside cockpit locker. Now I would like to describe how I installed the positive cables to the ACR and how I routed these cables to the fuses and bus bars in the confined space available on this backplane.
Let's begin by looking briefly at the finished job. On the far left is the bus bar for the house battery bank. Between it and the ACR there is an ANL style fuse. The next bus bar is for the reserve battery bank. It too is separated from the ACR by an ANL style fuse. Fuses are essential for protecting the cables. They are, so to speak, the weak link in the chain. Better for the fuses to blow and to break their respective circuits rather than the cables to overheat and to catch fire. I'll say right now that I did not initially plan to use ANL fuses for this job, but instead terminal block fuses. Read on to see why I altered my plans.
The yellow tabs on the Blue Sea Systems brand ACR hold the protective cover in place.
Beneath the cover there are two lugs, both 3/8 inch.
I ordered all my cables from Genuinedealz / BestBoatWire, an online retailer in Brunswick, Georgia. I learned about Genuinedealz from reading the many postings and online articles of Maine Sail, that marine electrician from Maine who does an excellent job explaining the complexities of marine wiring. For a sample of Maine Sail's work, check out the link to his Compass Marine website on the homepage of this site.
Beneath the many pieces of 12 inch heat-shrink tubing were the cables themselves, as well as the lugs that I would use to terminate them.
The cables were manufactured by Almo Wire and Cable in Philadelphia, Pennsylvania. These were not solid copper cables; rather, they consisted of many small strands of tinned copper. Stranded, tinned copper cables are the proper cables for boats, as they are more flexible and more readily resist corrosion. The lugs were manufactured by FTZ Industries in Simpsonville, South Carolina. All the lugs were heavy duty / heavy walled, and they were all tin-plated copper, designed to resist corrosion in the marine environment.
Earlier, I had ordered an FTZ brand heavy duty crimper, product number 94285. As per the advice of Maine Sail, I found that the best deal was at K. L. Jack & Company in Portland, Maine. This crimper was not cheap, but it was worth it. I cannot imagine trying to do this complete rewiring of Oystercatcher without it. Sure you can pay Genuinedealz one dollar in labor to crimp one of these heavy duty lugs on a cable. This would certainly be worth it, if you were replacing a some existing cables whose exact length was known. In my experience from this rewiring, I would have wasted a lot of money, if I had gone this route. There were just too many variables in terms of the twists and turns that almost all of the cables needed to make from start to finish.
At the head of the crimper there are adjustable dies, and on the handles there are charts which indicate which dies you must use for each size and type of lug you are using.
I found the whole FTZ crimper and lug system to be quite easy, as the lugs are color coded and have the proper die settings printed on them. The charts on the handles are good for double-checking, which I always do out of force of habit. It's sort of like that old saying in woodworking - measure twice and cut once.
Before I headed out to the boat, I assembled the necessary equipment.
For this part of the project I got a friend to give me a hand, especially since the crimping appeared as if it would require more than two hands. Here we see my buddy using the cable cutters to score the plastic jacket of the cable. This was 4 AWG cable, in other words, 4 gauge cable according to the AWG (American Wire Gauge) standard.
He cut just enough to allow the lug to fit snugly.
Nice and tight, with no exposed wire, just as Maine Sail suggests on his webpage.
Here's a close up of the adjustable dies for the crimper. To accomplish the crimping, my friend would stand inside the boat at the companionway and I would kneel in the cockpit. He would turn the crimper vertically (in other words, perpendicularly) to the teak you see pictured below. I would then hold the cable in my left hand and the lug in my right, holding the two firmly together while my friend made the crimp. This squeezing action on my part was necessary to prevent the lug from slipping off the end of the cable as the crimp was being made.
The completed crimp. As per the suggestions of Maine Sail, we made the first crimp at the base of the lug (here pictured left), and then we made the second crimp higher up. We also rotated the lug 90 degrees for the second crimp, so as to distribute the sharp edges and rounded edges that are created by the dies. I should note that we took these pictures for illustrative purposes at some point in the overall main circuit rewiring process. That's why this particular cable is not red.
Here we see my friend using the heat gun to make the adhesive lined heat-shrink tubing conform to the lug. This heat-shrink tubing helps to prevent the intrusion of moisture and thus the establishment of corrosion. Note that we've already slid a piece of clear heat-shrink tubing on the cable. This clear heat-shrink will cover the label that we'll soon apply over the red heat-shrink after it cools. Depending upon the size of the heat-shrink, it's often easier to slide the clear piece on in advance of the heating of the colored piece.
It was so much less strenuous doing this work in the cockpit instead of trying to do it in place on the bulkhead in the lazarette. This was the primary reason why I decided to use a backplane for this part of the main circuit.
The first cable that we made was the one that would join the house bank positive bus to the ACR. The Blue Sea Systems ACR allows you to install cables in one of two directions - either vertically, from the bottom, or horizontally, from the side. For this cable, the best approach was from the side. Note the cover in the background. The two slits on the left hand side indicate the "knock-out" portion of the cover. In other words, the consumer, if he chooses to install the cable from the side, can knock-out this plastic tab to allow access for the cable. You really don't have to knock it at all. You just wiggle it back and forth, and it breaks off quite neatly.
Notice that I have taken the time to label this short cable that joins the house positive bus to the ACR. Again, I followed the lead of Maine Sail on this. If you read his many online postings and look at his many outstanding pictures, you'll notice that he is almost obsessive about labeling. Many a person might wonder why it would be worth it to label such a short cable "ACR" when clearly it runs directly to the ACR. Well, I'll tell you why. Because, if you ever have to disassemble your main circuit to replace one item or another, you might have trouble putting it all back together again, if all of your cables are red and all of them are unlabeled. Part of the story of this article I'm presently writing, and which I've not yet discussed, is how I had to alter my original plan and my initial configuration to accommodate ANL fuses. In the process, I had to shift some things around. Having clearly labeled cables made it much easier for me to sort things out.
For all of this labeling I used the Brother brand labeler, Model PT-1290. It cost me about $20 at an office supply store. I was sort of upset at the time I bought it that the AC power cord was not included with it, and that, because of this, I would need to use AAA batteries to power it. I could have bought an AC power cord for $20, but that price seemed outrageous. As it turned out, the labeler was not power hungry, and one set of AAA batteries was sufficient for the entire rewiring project, and beyond.
There is a window on the bottom of the labeler which reveals the specific type of tape cartridge that is in the machine. I used the good stuff - the waterproof TZ tape. This was not the type of tape that came with the machine. I had to order this on my own from an online retailer. Once again, in using this Brother brand labeler and this specific tape, I was following the lead of Maine Sail. Lots of good advice.
Soon after crimping the first lug on this short cable I starting thinking about the terminal fuse block that I planned to install on the stud of the bus bar. The dimensions of this terminal fuse block would affect the length of the cable and thus determine how much I need to remove from the other end of the cable before crimping the second and final lug - the lug that would join this cable to the stud on the ACR.
Below we see the terminal fuse block, part number 5191, sold by Blue Sea Systems. I had read in Maine Sail's many postings and had noticed in his many pictures that he often used terminal fuse blocks to protect the cables that would join his bus bars to the ACR or some other item. Terminal fuse blocks typically are used on battery terminals to provide protection to the battery cables at the power source (rather than farther down the line). Maine Sail, however, as I noticed, also uses them from time to time on bus bars. This, to me, seemed to be a good idea for my set-up, especially given the space limitations I faced on a 25 foot boat.
I had not yet ordered the terminal fuse blocks for this set-up, since it was necessary to spread out my purchases for this complete rewiring of the boat over some period of time. I did, though, figure that I could still accurately determine the length of the cables I needed to make, simply by referring to the excellent specifications provided by Blue Sea Systems on their website. When I consulted these specifications, I discovered, much to my chagrin, that the terminal fuse block would not work at all with the particular bus bar that I had already purchased and installed on the backplane. This bus bar, like the two others, was a common, 150 amp bus bar with four 1/4 inch studs (Blue Sea Systems, part number 2303). The terminal fuse block holder contained a mounting hole that was 3/8 inch in diameter. This meant that if I installed the terminal fuse block on the bus bar there would be a gap of 1/8 between the bus bar stud and the terminal fuse block mounting hole. This meant that there would be poor contact between these two pieces of metal. This meant that this set up would not work. How could I have gotten this so wrong? That's what I wondered. After all, I had seen pictures of Maine Sail using terminal blocks on bus bars, and I knew that, being the stickler he was, he would not permit himself to do sloppy work.
Pausing for some time, I went back and hunted down some of the postings where I had seen him talking about the use of terminal fuse blocks on bus bars. Eventually, I found these postings, and then I discovered my mistake. I had assumed that all Blue Sea System bus bars were the same, in other words, that they all had the same size studs. The bus bars that Maine Sail had shown in his pictures were larger - the 250 amp MaxiBus bars by Blue Sea Systems. In pictures, these look no different to me than the smaller 150 amp common bus bars. Maine Sail did not say that he was using the 250 amp bars, but I could deduce this, because he said that the studs on the bars were 5/16 inch, which is what the 250 amp bars possess. Maine Sail, I should note, did say that despite the 1/16 inch difference between the 5/16 inch studs on the 250 amp bars and the 3/8 inch mounting hole on the terminal fuse block, he found this difference to be tolerable. I should also note that I had originally planned to use 250 amp bars in my set-up, since I figured that this size would be needed for the main circuit, especially since it would be handling the in-rush of amps from the motor whenever I started it. After using the Blue Sea Systems online Circuit Wizard, however, and after consulting with Blue Sea Systems' technical support person, I had determined that the 150 amp common bus bars were appropriate for my set-up.
All of this meant that for this particular set up, I would not be able to use terminal fuse blocks to protect the cables leading from the bus bars to the ACR. This was troubling, at least at first, because space was already very tight on this backplane, and I had not planned on adding anything else to it, except for the many cables that would snake around it.
Eventually, after some thought, I decided that the best thing to do would be to try to fit ANL fuse blocks onto the backplane. I had seen Maine Sail use these in similar situations, so I figured they would be a good alternative, assuming I could fit them into the space.
I began by mounting the one for the reserve bank bus bar horizontally, directly beneath the ACR. The second one I thought I might have to mount on the overhead of the lazarette. That's why I have the cable veering up and away from the house bank bus bar (far left). Throughout this process I had to take into account the other cables that would be joining the bus bars. Across the top of the back plane I would probably run the large, 1 AWG cables that would lead upward to the battery switch in the cockpit locker. Also I would probably run the positive cable for the battery charger across the top.

Mindful of the crowded space on the top side of the backplane, I eventually began to think that I should route the cable for the house bank bus bar downward (and then upward) to the ACR. I could not make any final decisions, however, until I did some more work in the boat.
With the backplane back in the lazarette, I began to make and install some of these other cables. I had already run the AC cables (gray conduit) and the AC grounding cable (black conduit) downward from the cockpit locker. These didn't appear as if they would present any problems.
Next, I ran the 1 AWG battery switch cables downward from the cockpit locker. These were the things I really needed to take into consideration.
In the picture below, you see the battery switch cables coming down. You also see the positive and negative cables for the battery charger coming in from the right hand side of the picture.
After holding up all of these cables with my hand, trying to get a sense of how they could all fit into this space, I eventually decided that the best location for the ANL fuse block for the house bank bus bar was between that bus bar and the reserve bank bus bar.
This allowed me to route the cable, or I should say cables, to the ACR in the most space-saving way possible. Note that in the picture below I have placed a cable on the top side of the backplane as a mock-up, just to make sure that I was allowing enough room for everything.

Later, after I had begun to install more of the other cables for the main circuit, I saw that my decisions regarding the location of the ACR and the routing of the cables to it through the ANL fuses had been a good one. Everything was starting to fit together well.
This ends this posting on how I installed the positive cables for the ACR in Oystercatcher, my Ericson 25. In the next posting in this series, I discuss my installation both of the LED indicator light and of the grounding wire for the Automatic Charging Relay.


  1. Thanks for taking the time to blog this in such detail. Very informative with the pictures to see it.

    1. Thanks for the compliment, Cook. If your read the second part of this article you should be aware that I made an error when I wired the LED indicator light. I routed the positive and negative wires opposite to the way I should have routed them. Seems counter-intuitive that the negative should join the ACR, but that's what is necessary. After I got everything installed the LED did not work. Thought the bulb was faulty. Had to go back and reroute the positive and negative wires. Have not yet made the correction to the second part of this article. Good luck.

    2. Thanks for the compliment, Cook. If your read the second part of this article you should be aware that I made an error when I wired the LED indicator light. I routed the positive and negative wires opposite to the way I should have routed them. Seems counter-intuitive that the negative should join the ACR, but that's what is necessary. After I got everything installed the LED did not work. Thought the bulb was faulty. Had to go back and reroute the positive and negative wires. Have not yet made the correction to the second part of this article. Good luck.