I’m upgrading some components of my boat’s DC electrical system. On the “Marine How To” web site I came across an article about a Blue Sea ACR, which included a wiring diagram (see below) of exactly what I’m trying to d, including adding ACR. Unfortunately the fellow who runs the website is not well, so I can’t ask him about the wiring diagram. The diagram shows four battery switches, three in the middle, plus one in lower left corner. I’m a little confused by the three middle switches in the diagram.
The article does not seem to indicate if this is a good or bad wiring system? (The article shows both good and bad). Why three battery switches? I’m wondering if anyone can enlighten me?
Thanks,
Don
‘87 NS 30U #369 Breezin’
Vancouver, BC
Personally, i find this system way over complicated. There are so many things to go wrong and they are all interconnected. I’ve never been in favor of paralleling batteries because If one of those batteries fails, it will take all of them down together. That 4th switch on the bottom left controls all of the battery outputs and if turned off, there is no power to the bilge pump. The middle switch is an override to connect the house bank to the starter. However, if the starter battery fails and the override switch is turned on, the failed start battery will take it down.
Have fun, Don,
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Don,
Based on the article, that would be considered a diagram of a good system. The system could be simplified but at the cost of some functionality.
The small switch in the lower left I will call switch 4. The other three I will call, Left, Centre and Right and collectively the 3 Main Switches.
The 3 Main Switches allow a number of options.
(1) Left switch on, centre off and right on. Lets the large battery bank run the house loads and the small reserve bank to operate as a dedicated starter. The battery banks are not combined.
(2) Left and centre switches on, right off. The main bank run the house loads and the starter. The small bank is reserved for emergency use only.
(3) Left off, centre and right on. The main bank is isolated and the reserve bank performs house (I think but not sure) and starter duties. This would be considered emergency mode and used when the main bank has a fault.
Switch 4 provides a convenient method of disconnecting the main bank for doing work on the electrical system without having to remove the positive lead (convenient). The way the system is wired turning switch 4 off would turn off the bilge pump. Forgetting to turn switch 4 back on and accidentally leaving the bilge pump off can be mitigated by wiring it directly to the main bank rather than through the bus bar. Removing this switch simplifies the system somewhat but it does require taking off the positive lead from the house bank when working on the electrical system (less convenient). My inclination would be to keep the switch and wire the bilge pump directly to the batteries because I like the ease of disconnecting the house bank but I know I would forget to turn switch 4 back on and not have the bilge pump available. Murphy’s Law indicates that is the very time the bilge pump would be needed. Of course my bilge pump has an Off, Manual On and Auto On switch located in the cabin where I can switch it off and forget to turn it back on.
The system can be simplified by removing the Centre switch. This would effectively give you the set up in number 1 above. Main bank for house loads and dedicated starter battery. If the starter battery failed you would have to changes the wiring to use the house to start the engine. If the house bank failed you would have to change wiring to allow the starter to run house loads. You could set up bus bars that would let you quickly make the cable switches if needed. Properly set up it would eliminate the risk of accidentally combining the two battery banks.
Aside from those two steps I am not sure how to simplify it anymore.
You may want to consider a battery isolator. A battery isolator let’s one alternator charge two batteries yet the batteries never “see” each other. You will not need any additional manual switches - simple to operate and nothing to forget to turn on or off.
Joe indicated the diagram you posted had the bilge pump after the disconnect switch. The bilge pump should be connected to the unswitched bus or directly to the positive battery terminal with a fuse. Fusing is a safety item so the boat does not burn up if a wire shorts to ground. Most Nonsuchs are lacking many necessary fuses. The boats may have been alright leaving the factory but over the years, owners adding stuff left out the fuses. On my boat, there were two factory wires run directly from the battery to a voltmeter at the DC breaker panel. Those wires were not fused. Notice that in the diagram you posted, every wire leaving the switched bus is fused. It is also a good idea to install a MRBF type fuse right at the battery to protect the wire going from the battery to the switched bus.
Take a look at the video in the link below. It gives a brief description of battery isolators.
Plus one to Ward’s suggestion of an FET isolator. I think Nonsuches came with isolators but they were the old diode style that turn a lot of your alternator output into engine room heating.
Also plus one on Pacific Yacht Systems and their entire line of videos. Jeff (Geoff?) can be a little long winded but he is a great resource when you are planning a re-wire.
We have a relatively simple arrangement. The two banks are connected to a Blue Seas SI-ACR Automatic Charging Relay. The single master switch is always set to Bank #2 which is the house bank. Bank #1 is the start battery. When the relay senses 13.1 V it connect the two banks as the 13.1 v signals a charge is occuring. The relay has a red LED wired to it and runs to just above the battery bank switch making it visible from the helm.
We leave the battery switch on Bank # 2 all the time. If Bank #2 were to fail we would turn the switch to Bank # 1 to start the engine. In the 19 years we have had the boat we have never had do that.
We have a 120 amp alternator depowered to 80 amps and a shore charger.
The wiring diagram that Don attached to his original post shows a Voltage Sensing Relay or ACR ( Automatic Charging Relay). The alternator feed to house bank (main bank) and when the voltage hits the preset level the relay opens and lets charging amps go to the starting or reserve battery. Some people wire the alternator to the starting battery to ensure that it always gets charged first and the relay allows charging of the house bank when the preset voltage is reached. Everyone has their own idea of which battery the alternator should go to.
Here are a couple of links to articles that lists the type of ways to charge two battery banks from one alternator. La Reina came to me with a split diode battery isolator. I believe it was installed by the factory. The problem was that it used old style blocking diodes that dropped voltage by .5 -1 volts which could lead to under charged batteries.The newer styled diodes discussed in the article do not cause as much voltage drop. The PBO talks about combining batteries but as has been pointed out in other replies there are risks with combing battery banks.
Wow 500 Ah is a lot of storage. My 48 volt series AGM string for my electric propulsion system is only 220 ah and my 12 house bank is two group 27 Gel cells. I live aboard most of the summer and my 150 watts of 12 volt solar panels keeps the house system topped up well. Since I pulled the diesel engine from the boat in 2008 I have not had an alternator on board either. A small Honda 2000 generator works well on the rare times I may need to charge things. Most of the time it’s just the EP bank. I’ve eliminated the starter battery too. I think most boats even those with diesels could eliminate the alternator and it’s charging complexity issues by employing, some solar and a small Honda as a charger and startup backup. Charging battery banks with three stage 120 volt chargers is easier on the batteries added to longer life too.
With regard to the question about battery switching, many people get confused by the dual a/b convention and I settled on a simpler solution to serve my most common use case. Using the Blue Seas dual circuit plus switch, you have two switched circuits (one for start, one for house) that are both either on or off. Then as a backup it has a combine function for when one or the other bank fails.
It would replace all 4 switches in the diagram above. KISS
With regard to the ACR, that is a completely separate choice, in no way dependent on the switch choice and while it does introduce complexity it is a convenient piece of kit to have there and if it fails you don’t impact the whole system. I have one since I got it at a heavy discount but I’m neutral on whether I would replace it if it fails.
One aspect of this diagram not discussed is that it simplifies the ground. Only one ground to the engine block. When I first bought my boat, I had many grounds connected to engine, it was a dogs breakfast! So over time I paired back all the grounds to a negative bus bar and used this diagram to have one to the starter ( the starter grounded to the engine), and then I set up a separate bus bar for non-current carrying (e.g. metal cases) to the engine block. I am also a local in Vancouver like Mark Powers and actually had Jeff Cote on my boat to do an electrical audit after I did my work, just to make sure. Chatty but knowledgeable and his videos are very good. However, some years later I swapped my ACR out for a FET isolator (I was having issues keeping the starter charged, something to do with my house batteries being larger than my starter). The latest FET isolators have a very small voltage drop, does the job, so when I start, the starter re-charges, and then is isolated. But in case I am stuck in paradise I have the three switches per this diagram.
Joe touched on a point re parallel batteries, mine are in parallel. However, I have a load tester that I used last year to test each of the 4 golf carts to make sure one of them wasn’t going bad, which would then mean all get replaced. I’m on year 8 with these flooded batteries, working well, just have to check the cells, keep the charger on so they are not heavily discharged, seems all ok for now.
I agree with Paul about the isolators. They were just big diodes and did fail. Took me a while to figure out dead battery problems on my boat when I first bought it. Got rid of the diodes, got a multi output charger and all the problems when away.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Joe, The multi output chargers incorporate a battery isolator, with FETs rather than diodes. That is how they provide a multi-output.
We are all learning as we go.
I’m repowering. The new Beta 35 will have two 120 amp alternators. The boat came with an ancient Balmar MC-512 voltage regulator which can control two alternators on one motor. Voltage regulator temperature probes monitor alternator and battery temperature.
I talked myself into 4 - Group 31 Oasis Firefly batteries. Three will be on the house bank. One will be for the starter. I thought I needed all the same battery type for charging purposes.
Today, in this thread, I was introduced to the Balmar Duo Charge. I think I like that. If I go with a Duo Charge, the output of both alternators will go to the house bank. The starter battery will be charged from the house bank by the Duo Charge. With the Duo Charge, I could have had a regular flooded lead acid battery for the starter and have saved some money as a result..
I want to send all of the alternator output to the house bank so that engine operation time for charging will be as short as possible. Even so, I may program the voltage regulator to derate the alternators by 25% to help limit alternator overheating. The alternators are driven by multi-rib belts so belt slippage should be unlikely.
I was referring to replacing the factory diode isolator between the alternator and the battery banks with an FET isolator. Nothing to do with shore power battery charging.
Hi All,
Thanks for the many replies. It’ll take some time to read or view all the suggested web articles and videos, but I’ll try to do so in the next few days. FYI, Pacific Yacht Systems is only about 3 Km (2 miles) from my house.
Thanks for all the help,
Don
