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Old 07-17-2012, 06:21 AM
WindEnsemble WindEnsemble is offline
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Default Another Wiring Thread

I'll spare you the details of how we came to trace our battery/selector switch/isolator/charger wiring. However, please see the attached image. It shows what we discovered. I can not for the life of me figure out why our system is wired the way it is. I have to assume a mistake, but being new to all of this, I am willing to be educated. So, refer to the diagram when considering the following. Thanks in advance for all insight.

1.) With both the starting battery (2) and the alternator connected to the starter solenoid post, the isolator always has voltage coming into A. This allows voltage from battery 2 to leak into the house bank. Wouldn't this effectively mean that battery 2 is charging the house when no other voltage source is applied?

2.) With this configuration I am unable to use the house bank to start the engine. That is, no reserve for starting the motor.

3.) The charger (which has recently stopped working at all) has the capability to charge 3 banks of batteries. However, only one DC out wire is connected and it goes to isolator post A, with the alternator wire. Shouldn't the DC out lines from the charger go directly to the batteries? Can the isolator handle that? Seems like it could. Can't imagine it (the isolator) cares what the input source is. However, I could find no document that suggested wiring it this way.

We have recently purchased a 10W solar panel that we intend for keeping the starter battery topped up. Ultimately, we'll have solar for the house side as well. Not just a top up charge, but a means for fully charging our house batteries.

Thanks,
Jeff

P.S. I read the article by MaineSail posted in another thread. Great information, but it does not consider the use of an isolator. I'm sure there's a good reason for that. :-)
Attached Images
File Type: pdf C36_Wiring_0712.pdf (111.8 KB, 58 views)
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1987 C-36 Wing Keel
Universal M25XP 23hp
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Coastal Alabama

Last edited by WindEnsemble : 07-17-2012 at 06:24 AM.
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Old 07-17-2012, 03:15 PM
stu jackson c34 stu jackson c34 is offline
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Isolators served their purpose well for many years, since they did what they were designed to do - they kept the banks separate when charging was not present. The reason they fell out of favor was because they induced a large voltage drop, anywhere from 0.7 to 1.0V, critical when charging. They have been replaced by relays or echo chargers.

Your wiring diagram is not unusual and works.

Was it Captain Sam's recent posts that included Maine Sail's writeups that you refer to?

What is it that you want to do?
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Old 07-17-2012, 04:24 PM
WindEnsemble WindEnsemble is offline
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Thanks for the quick reply, Stu. Yes, Captain Sam's thread was where I saw MaineSail's article. At this point all I'm trying to do is understand. What I expected to find when tracing the wires is in figure G in the following link.

4power.tripod.com/id40.html

It seems to me that having battery 2 connected to isolator post A, via the solenoid post defeats the purpose of the isolator. That is, battery 2 would feed battery 1 continuously when battery 2 is at a higher charge. Not to mention the inability to leverage battery 1 for starting.

My wife and I are exploring adding solar....yet another charging option, so just getting educated.

We will likely go with MaineSail's suggestions regarding configuring the charging circuits.

Jeff
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Old 07-17-2012, 04:24 PM
stu jackson c34 stu jackson c34 is offline
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Jeff, try this
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File Type: pdf Jeff 1.pdf (49.7 KB, 38 views)
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Old 07-17-2012, 04:51 PM
WindEnsemble WindEnsemble is offline
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Makes perfect sense. I am assuming PDP refers to power distribution panel. Or simply a bus? Do you have a recommendation?

Thanks a bunch for all your input.
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1987 C-36 Wing Keel
Universal M25XP 23hp
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Coastal Alabama

Last edited by WindEnsemble : 07-17-2012 at 04:59 PM.
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  #6  
Old 07-17-2012, 05:36 PM
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baysailor2000 baysailor2000 is offline
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Default Isolator -

Jeff - there are 2 items I would like to suggest.
1) Remove the wire that connects post no 2 of the isolator and post no2 of the battery switch.
2) I am pretty sure that your battery switch has a "Both" or "All" setting. This will allow you to use the house bank to start the engine if desired. In any case you must be able to charge all batteries when engine is running or using the 12VDC charger.
That is how is done on my boat. Initially I could not understand why one side of the isolator was disconnected - but I now see why and you are right that the 12V battery may be charging the house-bank when the house-bank become low in voltage.
Regarding the way that the charger is connected to the batteries - I must admit that I have not looked at that yet on my boat - but I will say that remembering the size of the cables coming off the charger I believe that they are connected directly to the batteries.
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Old 07-17-2012, 05:36 PM
stu jackson c34 stu jackson c34 is offline
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Jeff, it's Positive Distribution Post, as discussed in Sam's thread. The place to connect your solar panel, too.
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Old 07-17-2012, 06:44 PM
WindEnsemble WindEnsemble is offline
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Excellent. Thanks again.
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Old 07-17-2012, 06:58 PM
WindEnsemble WindEnsemble is offline
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Quote:
Originally Posted by baysailor2000 View Post
2) I am pretty sure that your battery switch has a "Both" or "All" setting. This will allow you to use the house bank to start the engine if desired. In any case you must be able to charge all batteries when engine is running or using the 12VDC charger.
Yes, the switch is (left to right) 1 - ALL - 2 - OFF. However, there is no connection from C on the switch to the starter. The only wire coming off of C goes to the DC switch panel. So, the battery selector switch plays no part in starting. Battery 2 is wired directly to the starter.

Stu took the time to edit my diagram and offer a better solution. See his attachment in his post above.

Thanks,
Jeff
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Coastal Alabama
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  #10  
Old 07-17-2012, 07:13 PM
TrueWind
 
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Default Take what you like and leave the rest.

Jeff

As an ABYC certified Electrical Tech, my advice would be be replace the isolator with a voltage-sensing battery combiner.

The combiners do not suffer from the inherent voltage drop of a diode, typically about 0.7 volts. Like the diode types, they must be amperage rated to match the maximum alternator output.

A couple of thoughts on solar charging/wind generators:

1. These devices need voltage regulation. Extensive tests have shown that both devices can have output voltages that approach 20V in some cases.

2. These devices also need blocking diodes installed in their output conductors. In the case of solar panels, the batteries will back-feed through the panels when the sun goes down without a diode to stop this reverse current flow.

Hope this helps a little.
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