All charging sent to House battery system...

[DDO]

...so, what do you think? I've collected all charging to the House battery bus bar. I've a House/Start 2-battery 12v system on my sloop. This is as advised by Blue Sea Systems. Finally this week I am adding the fuse and Service Disconnect Switch for the (37A) alternator. While revising my electrical drawings, I noticed the alternator has a little blue wire going to the coil +, in the Start battery system. Shouldn't it instead go to some location in the House battery circuit? Just a thought I had, but can't find info about.

[ndutton]

There are a lot of opinions on what is the best charging system design but what none of them take into account is what is best for you, your boat and most importantly, your troubleshooting skills when the time comes.

Not singling out Blue Sea Systems but I'm always wary of recommendations from entities with a financial interest in your decisions. Here is a post from a few years ago that makes the points I've mentioned. You can read the entire thread by clicking on the thread title in the upper right corner. Neither of the drawings in the link were from Blue Seas but one of them was from a professional marine electrician. Guess which one.

http://www.moyermarineforum.com/forums/showpost.php?p=103924&postcount=19

[joe_db]

...so, what do you think? I've collected all charging to the House battery bus bar. I've a House/Start 2-battery 12v system on my sloop. This is as advised by Blue Sea Systems. Finally this week I am adding the fuse and Service Disconnect Switch for the (37A) alternator. While revising my electrical drawings, I noticed the alternator has a little blue wire going to the coil +, in the Start battery system. Shouldn't it instead go to some location in the House battery circuit? Just a thought I had, but can't find info about.

You have a few issues going on and this may not work out as you planned. I too run my alternator to the house bank and Blue Sea ACR connects the start bank for charging. My external regulator has an ON wire and a SENSE wire. The ON wire in your case is the blue wire. It tells the regulator to turn on when the ignition is on and off when it is off. My ON wire is connected to that and the SENSE wire runs to the house battery. The Balmar regulator uses that sense wire to adjust the output voltage of the alternator.
I cannot recall if the stock Motorola setup senses voltage from the connection to the battery or the ON wire. If it is the former, you are good. If it is the latter you will have a big issue when the batteries do not combine for some reason and the alternator is driven to full output because the voltage on the start battery stays low.
The next issue is the alternator itself. I had one of those and 37 amps is minimal to start with and then the regulator was set to 13.8 volts on mine, which is way too low for bulk charging. I ruined an expensive battery by undercharging it way back in the day. An external regulator will solve your low voltage issue, but you will then be running that alternator hard and it will end up in the shop sooner or later. I would seriously think about your next steps being a bigger alternator and better regulator. There are several ways to accomplish these steps at varying price points including equipment from our hosts

[DDO]

Alternators

It has run this way for a dozen years great, but I have never had a bad battery etc. for the system to deal with. I understand if blue wire is ON it must go to Starter circuit (ignition) and SENSE must see the charging battery (in my case, HOUSE). Right? Regulator on mine is internal. I will ask at the shop I bought the alt from... I replaced the Motorola years ago with a OEM 37A replacement. I have never had a reason to up-amp or I would have bought Moyer 55a alternator since I love buying from Moyer. By the way, Blue Sea is a Bellingham (my town) company -- the employees, engineers are our local folks -- but alas there isn't something like a local "factory outlet" store to get these things wholesale. Thanks.

[joe_db]

What are you using for a combiner?

[DDO]

Not a Blue Sea ACR, a West Marine Combiner-50, which I think is Yandina 50. Seems to be continuing to work nicely year after year. It's a little thing. What do you think?

[DDO]

The little yellow wire gets a name...

I noticed lots of educational posts now. But now I am again confused by the vocabulary in these posts. Is the "ON" also called "EXCITE" or "SENSOR" .... are these 3 different things or two different things that get renamed.... See my confusion? It seems clear that one is about ignition and one is about voltage state, but I don't follow the naming.

[joe_db]

Here is the issue. I do not know how the stock Motorola regulator senses battery voltage. It only has one connection to it, the wire that turns it ON or OFF. If you apply voltage to it, it goes on. If not, it goes off. It usually runs to the coil from the alternator.
The regulator might use that wire as a sense wire or it might not. The only other choice is to use the battery connection (thick wire from the output stud).

How to test:
With the batteries NOT combined and pretty much fully charged, run the engine. The house bank will be getting charged. Check the voltage at cruise RPMs. If it holds 13.8-14.2 or so, it is doing fine. If the voltage runs up significantly higher and varies a huge amount with RPM, STOP. IN the second case it is sensing the not-being-charged engine battery.

[Al Schober]

Been a while since I used the stock 35A Motorola, but as I recall it had only 3 connections - 12V in, field current out, and ground. Ground was to the alternator case, the field wire was tucked under the regulator case and disappeared into the alternator, and the 12V input went to 12V. The 12V connection was either alternator output or coil +. It was also the 'sense' wire.

50 years ago, boats had the A/B switch so you could use one battery for house loads, reserving the other battery for starting. When one battery went flat, this allowed you to switch to the other one for starting. Too often, the other one was also flat! These batteries were usually close to the engine keeping heavy cable runs to a minimum.

Current systems use a dedicated house bank and a smaller starting battery. The start battery is close to the engine while the house bank is closer to the distribution panel. For charging the house bank, the cable from the alternator to the house bank only has to handle alternator output, while the cable from the combiner (VSR) only has to handle the acceptance current of the start battery. Ditto for the ground cable connecting the two.

The alternator controller needs a 12V source. If this is also the sense voltage, it has to be connected to the house bank. It can certainly be connected to the alternator output. Whether it can be connected to coil + depends on whether engine ignition comes from the start battery or the house battery. Most current systems, the engine has its own on/off switch which controls both current to the starter and current to the ignition.

IF you want the capability to use the house bank for emergency starting, then you need to add the switch for the emergency connection PLUS you need to run larger cables capable of handling starting current for both the positive AND the ground leads. In my case, I chose not to provide the switch & heavy cables. My 'emergency' start system was to physically move a battery.

[Sam]

Al, I am smiling a little because my 1966 Morgan 34 has an A-B switch and batteries on each side of the engine. Very old school but simple to work on.] [Ignition switch cuts off power to coil and starter]. I am starting to think I better upgrade before I am too old and too late.

[DDO]

Thanks everyone. So, none of us know which of 2 possibilities the little yellow wire connector really is. (Above I mention it as a blue wire to coil+.) But it iss all more clear to me now. For those interested: I have 3 "use" switches - start or house and "both". "Both" can switch over or combine, although I've never needed to do either. I like this arrangement, but added little LED lights for indicators. On other's boats I found the one-big-selector-switch confusing because they each have different variations from different decades.

[joe_db]

We know it turns the alternator on, what we don't know is if it is the sense wire too. I doubt it is, but it is worth checking.
Here is another strategy to check.
Get a 12 volt battery from somewhere and connect the - to ship's ground.
Disconnect the turn-on wire.
Run the engine.
You should see no output from the alternator.
Connect the turn-on wire from the alternator to the battery you brought.
If the boat batteries charge at 13.8-14.2 or so, all is well.
If it drives the alternator to full output, then the turn-on wire is also the sense wire.

[DDO]

Thanks. Yes, Joe, my blue (yellow) wire is indeed just the ON wire, called "Ignition Wire" and it is not also a sense wire. I did finally find the # for the alternator and, in turn, the regulator part number, and found it in their catalogs to comfirm. Thanks to these posts I now know what would have happened had it been moved and why it all works well. For a good time, I plan on doing the tests, as I have a new better multimeter.

[joe_db]

Good news - if the alternator senses on the output terminal, it will be able to set the voltage correctly for the battery it is connected to.

Next step - verify the charging voltage. If it is 13.8, charging will be slow. There are relatively cheap ways to fix this.

[ndutton]

Good news - if the alternator senses on the output terminal, it will be able to set the voltage correctly for the battery it is connected to.

Are we suggesting a Motorola 37A alternator puts out variable voltage? I hope not but that's what I think I just read.