ACR with alternator and AC charger

I'm going through the endless process of untangling and updating the wiring on my 1981 CHB.

I would like to wire up the alternator with an ACR (automatic charging relay), so anytime the engine is running the alternator charges house + engine bank. However, in doing so the ACR switch will be active when the AC charger is powered, which is about 300 days year.

Is it ok to keep the house and engine banks combined for that much time, with AC charger? The house and engine are sized differently, conventional wet acid chemistry.

I have done what you propose for years with no affect on the batteries. It helps that both house and starting batteries share the same chemistry. It really isn't any different than hooking up a shore power charger with two separate outputs to the separate battery systems. Almost all dual output shore power chargers use the same charging algorithm for both outputs.

As long as you are untangling wiring, consider wiring the alternator output to the house bank instead of the starter terminal where it is wired on most engines. The bank that needs the most current routinely- the house bank is the one where the alternator output should preferably be wired to.

David

A smart combiner will solve your issue.

https://www.magnum-dimensions.com/smart-battery-combiner

No problem. The charge source couldn't care less how many batteries are in a bank, and when combined, you've just added another battery or two.

winty said:

I'm going through the endless process of untangling and updating the wiring on my 1981 CHB.

I would like to wire up the alternator with an ACR (automatic charging relay), so anytime the engine is running the alternator charges house + engine bank. However, in doing so the ACR switch will be active when the AC charger is powered, which is about 300 days year.

Is it ok to keep the house and engine banks combined for that much time, with AC charger? The house and engine are sized differently, conventional wet acid chemistry.

Click to expand...

Yes, this is completely ok.

Ken

Yes, as mentioned above, this is fine. I like David's advice to wire the alternator to the house bank. I do this and use a switched Yandina 160A combiner to share the charge, when needed, with the start battery. Like you, I have same chemistry batts....FLA.

I have a Promariner 60 amp charger hooked to my 2 4D start batteries and to my house bank that is 4 6 volts in series/parallel configuration. I have 2 Blue Seas ACRs that connect each of the 4Ds to the house bank for charging when underway. When I hook up the boat to shore power or generator, I have a on/off switch in the ground wires coming off the ACRs that I turn off which removes the ground reference on the ACRs. It effectively disables the ACRs. When I installed the ACRs I called Blue Seas and asked them how it would be possible to disable the ACRs when on shore power. In looking at the schematics I realized when on shore power the banks would combine as soon as the voltage reached the preset threshold. BS recommended 3 solutions. One was the on/off switch. Two was a 120 volt relay to break the ground when on shore power. Three was to buy their battery charger so that ACRs could be cabled to it and the charger would turn off the ACRs. I went with the switch. I have to remember to turn it off when I plug into shore power or the genset but that isn’t a big deal since I am at the main electrical panel anyway.

Comodave, I have a similar switch function on the Yandina. It works great for my purposes. When I last left the boat, I didn't know how long I'd be gone....maybe a while, so I left the start batt on the float charge. Went to the boat today after a month away with the batts paralleled. Turned off the switch to stop charging the start batt. Today when I left, knowing I'd be back within a week or two, left the switch off since the start batt is fine without a float for several weeks. I like the flexibility on sharing the charge without the risk of paralleling the loads.

What are you starting with those 2 4Ds? You might be carrying around a lot of dead lead as, IIRC, our illustrious CMS called it. Have you ever considered one G31 start battery and a larger house bank with a couple more GCs?

I have twin Lehman SP225s. I know that I could get by with smaller start batteries but the battery boxes are custom made for 4Ds and the house bank isn’t near so I cannot use any of the space to enlarge the house bank.

Wintry
You might want to take a look at what I did and why when redoing my alternator & AC charging scheme.
I looked at Blue Sea ACR but decided on a Sterling CVSR.
Schematics and rationale all can be found at Bacchus website - Projects - page through to find the Charging System Mods
http://dkloeber.wixsite.com/bacchus

Comodave - I'm sure I'm going to reveal my ignorance again, but would another option just be to leave the battery charger lead off the start battery and go ahead and let the ACR combine while on shore power to keep the start batteries charged?

I suppose you could, but I would go ahead and hook it up. I think that you would get a better and maybe quicker charge on the start battery. Smart chargers look at eack bank and charge them according to their need. If you have 2 banks combined all the time they mau not charge as well. I just have an on/off switch inline with the ground sense wires on my ACRs. When on shore power I just turn the switch off. I have to go to the main power panel when I am hooking/unhooking to shore power anyway.

Thanks for the replies. Attached is a crude schematic (learning Sketchup) feedback much appreciated.

• Delete OEM battery selector switch at the breaker panel. Wired with 6AWG and runs hot under AC charge load.

• Deleted engine start combine solenoid in ER

• ER install house positive busbar

• ER install alternator/charger shunt

• ER Install ACR

• Install ACR bypass switch at the breaker panel

• Engine start ACR bypass

• ER engine start main battery switch

• ER start bank positive busbar

• Correctly sized terminal fuse installed at each battery (sized to wire rating not load).

• Replace helm amp meter with a voltmeter

• Install shunt supplied amp meter at breaker panel (monitors alternator or AC charger output).

Missing ability to start from house bank (I have jumper cables)

No house bank main disconnect switch... The house bank is fused, is that enough?

Larger labels

winty said:

I'm going through the endless process of untangling and updating the wiring on my 1981 CHB.

I would like to wire up the alternator with an ACR (automatic charging relay), so anytime the engine is running the alternator charges house + engine bank. However, in doing so the ACR switch will be active when the AC charger is powered, which is about 300 days year.

Is it ok to keep the house and engine banks combined for that much time, with AC charger? The house and engine are sized differently, conventional wet acid chemistry.

Click to expand...

Most "multi-output" chargers are doing nothing differnt than what an ACR would.

winty said:

Missing ability to start from house bank (I have jumper cables)

Click to expand...

If you use an ML-ACR 7622 instead of the 7610SI ACR you will have a manual or contura switch operated parallel option.

winty said:

No house bank main disconnect switch... The house bank is fused, is that enough?

Click to expand...

This is a requirement under ABYC standards.

Beyond that having seen numerous start motors "stuck on" over the years you'll be very glad you have a switch to cut power for a starter motor or a house bank..

About ten years ago I was on a racing sailboat 160nm offshore when I caught a faint whiff of burning electrical. In a split second I dove below and cut both battery switches off. The rest of the crew had no idea what was even going on. The shorted wire, a friction-fit/Fast-On type terminal, only partially insulated not fully insulated, had come loose in the rough seas and shorted and physically welded directly to a DC neg bus.

By the time I cut DC power the 10GA wire had already turned from stranded to solid copper and had zero wire jacket left. It was in the process, & very close to, igniting a piece of wood it passed over.

If I had not had the ability to cut all DC power, and do so quickly, the likelyhood of a fire 160nm offshore was very, very real. While we did have the race rules required offshore equipment, including a life raft, no one wants to actually use those.


This boat did not require a battery switch or a battery fuse and a single G-24 battery did this when the battery cables shorted. Sometimes the ABYC standards simply don't go far enough and common sense needs to take over. Just seconds before this Boston Whaler ignited a few 8 year old "junior sailors" and their coach were on board.

House bank (not used for engine start). In the case of wire short, will a properly rated fuse at the battery terminal prevent a fire? Vs a fuse + manual cutoff switch?

winty said:

House bank (not used for engine start). In the case of wire short, will a properly rated fuse at the battery terminal prevent a fire? Vs a fuse + manual cutoff switch?

Click to expand...

A fuse at the battery will help in the case of a short circuit. There are many other reasons why you would want to quickly disconnect a battery with a fuse being of no help.

Comodave said:

I have twin Lehman SP225s. I know that I could get by with smaller start batteries but the battery boxes are custom made for 4Ds and the house bank isn’t near so I cannot use any of the space to enlarge the house bank.

Click to expand...

Our 1988 CHB Present has an identical battery set-up with two huge 4D's as starting bats. I also combine the house and starts while running in order to charge both. Dread ever having to take those 4Ds out, but they are only two yrs old, so maybe not for a while I'm still learning about all of the systems on this boat - oh, the joys! Next I will install a 50 amp galvanic isolator, just in case.