ACR Wiring

Scott T-Bird · Monday at 10:51 AM

There should be a direct link (positive cables) from each battery bank to the 2 + posts on the ACR. Also, the alternator should be linked directly to the larger bank (most likely the house bank), so you will want to re-route your alternator output to the house bank. Read this article and pay close attention to the diagrams (both correct and incorrect examples:

Making Sense of Automatic Charging Relays - Marine How To

Making Sense of the ACR WARNING: ACR's are not for use with LiFePO4 Batteries! What is an ACR? An ACR is nothing more than a fully automatic, voltage triggered, BOTH/PARALLEL switch that closes when charging voltage is present and opens

marinehowto.com

Scott T-Bird · Monday at 10:54 AM

It looks like you want isolation between the house bank and the start bank, which is understandable. I'm not sure why you would try to do it this way instead of using a DCP switch (replacing the 1+2+B switch).

dlochner · Monday at 1:00 PM

moe_1200 said:
Working on a complete rewire of a 1981 Catalina 30 and I'm looking for some input on how to wire in an ACR to charge the 2 different banks. I have a crude drawing of the primary battery wiring diagram as I have currently laid it out. I know my battery selection switch wiring is a bit unusual in that the output of this switch goes only to the house system (lighting, radios, fresh water systems, GPS) and does not go to the engine wiring directly. I want to keep the engine circuit separate with the ability to shut all power to this circuit while underway without impacting any of the other systems. However even though I'm keeping this separate I want the ability to charge both banks with the alternator while underway. My question is how does the current setup look and where would you place an ACR into this arrangement? Would it be worth running the extra wire from the alternator to the house bank rather than jumping back to the primary post on the starter? All wiring shown is 4AWG.

I forgot to mention that the Batt selection switch would almost entirely only reside on bank #1 so the house system is never pulling from the engine bank even though you potentially could. If I switch to "both" I should still be able to use the house bank to start the engine.

Alternator out put goes to house bank (fused at the battery with a large enough cable). ACR goes from the House to Start battery.

Get rid of the 1-2-B and as @Scott T-Bird suggests get a Blue Seas CP+ switch and read the article he linked to.

marcham · Monday at 1:10 PM

What type of switch do you have for the house bank?? 1 / 2 Off ? That could seriosly confuse anyone who uses this boat after you....

A few assumptions:
- you have a small alternator (60 A or less). You have AGM and/or flooded batteries...
-no lithium batteries or plans to install lithium in the near future
-no solar / wind turbine or other charging sources
- all wires are tinned marine cable, with tinned lugs which have been crimped with a calibrated crimper (crimp one, cut it apart and inspect to ensure the required compression/fusing has been achieved).

Do you have a shore power charger? single bank or double bank? (that will affect how the ACR is wired).

If you want isolation:
ON/OFF switch between house bank and house panel (with bilge pump and CO/propane alarms wired directly to the battery via small fuse). You need a fuse between the positive post and the battery switch (within 7" of the terminal), if the fuse is further, the wire must be fully protected from chafe and wear.

ON/OFF switch between the start battery and the starter. The alternator is normally wired to the starter. A fuse is optional, although for most small engines, a 300 A MRBF works well in this application.

If the ACR fails, you also need / should install another means of combining the two banks. This can be done with an addititional ON/OFF switch (ideally a different color). If all your batteries are in the same area, another way to simplify the install is with the Blue Sea 5511E battery switch, which normally keeps each bank seperate, but they can be compined if the ACR fails (or for when the house batt goes below the min combined voltage on the ACR). This could also be used for emergency starting should the start batt fail.

Running a new wire from the alternator direct to the house bank makes sense if your house bank chemistry can accept a significant higher charge current than your starter battery. If it's all AGM, I wouldn't bother. As your start batt fills, all the current will naturally flow to the house batt.

If you desire to use different charge profiles for each battery bank, then the ACR won't do that for you, you would need a DC-DC charger.

ACR can be wired on the battery post side or on the battery switch side of the system (load side). If on the battery post side, it will activate when your shore power charger powers up or when sufficient voltage is provided by the alternator on the starter batt. Requires large fuses near the battery for the 2 red wires going to the ACR and requires a fuse for the negative wire going to the ACR. Ideally, should be placed somewhere where the green light can be easily seen when required for troubleshooting.

4 AWG may be on the small size for the starter, we would need to know the engine make/model (starter watts) along with the total wire run length (to the engine and back) to determine if that's appropriate or not. I normally run 1AWG (min) and up to 2/0 AWG for small pleasure craft starter wires.

You'll need an appropriate fuse between the starter batt switch and the engine instrument panel. Normally the engine instrument panel is powered via the engine wiring harness and not hooked up directly to the battery.

PS: the Blue Sea manual for this product is excellent and shows the installation methods and lists the required supplies.

I'd strongly recommend purchasing ABYC E-11 if you are going to take this on...it's under $100.

marcham · Monday at 2:00 PM

Seems like you have a good handle on things and want to make it right!

That Universal engine ammeter wiring was the cause of many boat fires....
Based on that setup, and assuming the alternator is now directly wired to the start battery.
I'd install the ACR on the load side of the battery switches, so that it only engages when you are actively on the boat / engine running. With boat battery switches off and the 3 bank shore power charger connected directly to each battery, the ACR will not activate.

Since you're in there anyway... there is also the option to install a starter inhibit wire on the ACR. This avoids any voltage spikes affecting the house loads while the engine is cranking.

I don't know your exact setup (wire run length), but my calcs have a min 2 AWG for the starter pos and neg wires.... 1 or 1/0 would be better (less voltage drop = less load on the starter and faster starting generally...). 4 AWG is fine for the ACR wiring, remember that fuses are there to protect the wiring, not the device. Max 4 lugs per screw/terminal.

Have fun !

Stu Jackson · Monday at 4:05 PM

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009

)
1/2/BOTH Switch Considerations

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough diagram: Building a Good Foundation (October 2016)
Building a DC Electrical Foundation

The Short Version of the 1-2-B Switch Stuff: Electrical Systems 101 This is a link to the Electrical Systems 101 Topic, reply #2

How to properly wire & switch a DCP switch - Maine Sail's "workaround" explained Replies #28 & 29
What size fuse for automatic charging relay?

Maine Sail's DCP Wiring Diagram
Operating the House/Start battery selector

Scott T-Bird · Monday at 4:05 PM

Be sure to study the diagrams in the link - particularly the diagram under the heading "Connecting Other Charging Sources". The ACR does not have a cable directly from the ACR to either switch. There should be nothing between the ACR posts and the battery banks except fuses at the battery. Since you are installing an ACR, the alternator output should be re-directed to the house bank. Because you have another charging source (shore power charger) you will be best served by installing a positive buss bar between the house bank and the battery switch. The DCP switch is intended to be sold with the ACR (that's how it will be packaged) because it is intended to be used together. (There is no purpose or reason to install an ACR with a 1+2+B switch).

If your buss bar is located within 7-inches from the house battery post you can install the fuses at the buss bar. You have options which type of fuse and fuse holder you can use; but obviously choose the appropriate style for the size fuse you will need. By using a buss bar as shown, you will have made an appropriate link between the ACR post and the battery post (I would not advise going directly from the ACR to the switch).

dlochner · Monday at 4:10 PM

Scott T-Bird said:
There should be nothing between the ACR posts and the battery banks except fuses at the battery.

Fuse at both batteries. MRBT fuses work well for this.

Stu Jackson · Monday at 4:11 PM

Scott T-Bird said:
(There is no purpose or reason to install an ACR with a 1+2+B switch).

Sure there is. You could use B to charge both banks when charging sources ARE present, for single output chargers and alternators - but then you have to go turn the switch when you shut the engine off. This was one of the reasons Yandina invented the combiner in the first place. And this was over 30 years ago: to avoid forgetting to do just this. It's actually in their manual!

Otherwise, Scott, your contributions here are very helpful. Just keep remembering to add the caveats on the DCP switches.

Scott T-Bird · Monday at 4:21 PM

Stu Jackson said:
Maine Sail's DCP Wiring Diagram
Operating the House/Start battery selector

Stu makes a valid point that the ultimate safety concern that should be considered when using the DCP switch is that the battery banks can physically be combined erroneously if one of the banks has a short or is dead beyond redemption. That is why the combined position is highlighted in yellow with a warning! It is a weakness of using this switch - but you can easily have the same problem with the 1+2+B switch so I wouldn't call it a disadvantage) You don't want to combine banks if one bank can jeopardize the other bank when they are combined. In my experience, this would be a completely rare occurrence (I have never experienced it during 20 years of using the DCP switch). That said, the safest installation would include having an on-line "on-off" switch between each battery bank and the DCP switch (in the positions shown on the diagram in the above link) so that a catastrophically failed battery bank can be isolated in the event that the "Combined" switch position on the DCP is needed. It's not essential because in a catastrophic failure, the failed battery can simply be disconnected for safety. I have the 2 on-off switches installed in my boat and they are hidden from view so that they can't be casually switched "off" (they are always "on").

Scott T-Bird · Monday at 4:29 PM

Also, when you install a buss bar and connect the charger to it, you do not need to use individual feeds to the batteries. I suppose it may depend on the charger, but you should just use one feed. My instructions say that it is not necessary, but Maine Sail recommends placing jumpers across the 3 posts on the charger, which I have done. I have a Sterling charger - same as the Pronautic charger.

ACR Wiring

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