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Faster 02-23-2013 07:00 PM

Alternator wiring issue...
Gents.. When we bought our boat it had what I was told was a 'home made' alternator field current controller (a PPO was an electrical engineer)- with an off/on switch, an adjustment pot. I don't think it actually functioned as we have an alternator charge current meter and were unable to 'see' any change. btw one of the wires involved in this scheme actually 'entered' the body of the alternator - not on any factory connection.

When we had our alternator upgraded and overhauled the shop said just to leave that field wire disconnected, that it was now ineffective and not needed (same could be said for the 'controller', I guess)

We are just about to order and install a Balmar 614 smart reg, and I wanted to fully suss out what was 'there', and the drawing below reflects what I think I've found.

From my internet searching it seems I only really need the output line, and the tach line and the blue D wire, which I assume to be the field and which is now common with the B+. I'm not charging very efficiently and I'm now wondering if part of the issue is this setup (initially to accommodate the 'controller') I even have a hand drawn schematic of that device, it's still in place but 'turned off' and disconnected at the alternator. Seems I should be able to simply remove everything associated with that old controller - but what about the blue wire? I'm assuming the Balmar will make use of it separately?

Gotta love years-old mickey duck wiring schemes......

Any ideas? I guess my main questions are:

1. Is this setup as shown (that's what's there now) a workable one?

2. Should I just cut out everything associated with the 'controller'?

3. Any other issues wrt to wiring in the Balmar?

Capt. Gary Randall 02-23-2013 07:18 PM

Re: Alternator wiring issue...
hello there, I am assuming that D+ field is directly connected to battery positive? in wiring scheme there will always be a current draw from your batteries. D+ field should be connected to the ignition switch on your engine and in the off position when your engine is shut down. It also should be on the other side of the shunt where it can monitor the voltage directly accurate/ ignition switch. The fact that you have an internally regulated alternator should be good in itself, as long as the field can monitor the voltage on the other side of the shunt. ( ignition switch) I would remove all the other homemade regulator and once the field can monitor the correct voltage you will find a improvement in the way your charge gauge reads. Directly because it cannot read correctly on the alternator side of the shunt assuming that you are using a amp gauge that is controlled by the shunt. Hopefully I have helped you out here. CaptG

Faster 02-23-2013 07:26 PM

Re: Alternator wiring issue...
Thanks Gary.. to clarify, it's wired exactly as shown.. essentially D+ and B+ are joined 3 inches from the alternator plug, then that carries on to the battery isolator. With the isolator in line I suppose we're not 'directly' connected to any battery positive.... This is what makes me wonder if that alone is inhibiting my charging capability.

I have no problem going to a smart reg in any event, but I'm thinking this may be part of why I feel our alternator is under performing.

Capt. Gary Randall 02-23-2013 07:44 PM

Re: Alternator wiring issue...
B+ should be wired to common on battery switch D+ should be wired to ignition switch so there is no current running to D+ when the engine is off. With this option you can charge either your house bank or your engine bank or both. This will also allow the shunt to read accurately,provided all connections to the shunt are clean. with this wiring configuration you should not need another regulator other than the internal regulator on the alternator.

Maine Sail 02-23-2013 07:58 PM

Re: Alternator wiring issue...

Lose the diode isolator. Lose the home made parts. Make sure your alt has been wired for external regulation. D+ on most Bosch alts not a field terminal. The D+ term on most Bosch alts is for a dash lamp. It uses the dash lamp to excite and start up. Any good shop can bring a field wire out for you. Be sure it is wired as a "P" type for the field..

Faster 02-23-2013 08:08 PM

Re: Alternator wiring issue...
Thanks, Maine.. when you say 'lose the isolater'... do I replace it with something else? Actually in light of all this I'm considering tossing the mess and starting over with a Balmar/equiv alternator too.....

Capt. Gary Randall 02-23-2013 08:24 PM

Re: Alternator wiring issue...

Maine Sail 02-23-2013 08:26 PM

Re: Alternator wiring issue...

Originally Posted by Faster (Post 994130)
Thanks, Maine.. when you say 'lose the isolater'... do I replace it with something else? Actually in light of all this I'm considering tossing the mess and starting over with a Balmar/equiv alternator too.....

You can replace it with a Balmar Duo Charge, Automatic Combining Relay, Echo Charger or one of the Sterling battery to battery chargers.

When you do any of these upgrades;

1 run the alt output B+ direct to the house bank

2 run the MC-614 voltage sense wire direct to the house bank

3 Use the same sized neg wire for the alt as you have for pos and make sure it too has clean connections back to the house bank. (preferably NOT though the engine block)

4 insert a Duo, Echo or ACR between the house and start banks and let it take care of the start battery.

5 Install fusing for the alternator output and sense wire within 7" of the house bank + terminal.

6 It is a good idea to fit a "service disconnect" for the alt output in the engine room so when working on the engine the alt is not live.

7make sure that shunt is robust enough for the output of that alt and those connections are good and clean. Any shunt in the + wiring should be 100% protected from shorts by means of covering it. This is why most battery monitor shunts are installed in the neg lead not the pos..

If you have a battery monitor you could also get rid of the alt shunt and ammeter.

Capt. Gary Randall 02-23-2013 08:30 PM

Re: Alternator wiring issue...
as you can see I'm not much of an architect/lol but if you can figure this out and wire it the same I think you will be very satisfied with the charging system. Remember the important thing is that your shunt is wired on the wrong side of your field/therefore it cannot read voltage drop which is the way that your internal regulator is supposed to work. It is being fooled because the field is wired directly to battery positive. It cannot sense how much voltage you are using. Therefore if you wired to ignition switch it will not only read the requirement but also show a discharge when appropriate on the amp usage gauge . CaptG

Faster 02-23-2013 08:39 PM

Re: Alternator wiring issue...
... taking notes.... much thanks :)

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