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Old 04-15-2017, 03:16 PM   #1
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Question Setting up Battery isolator - Alternator problem?

Hi Guys,

In need for help, I'm stuck.
I'm trying to set-up a battery isolator on my bus , the diode kind, a Sure Power 200A 1 input 2 output. My engine is a T444E.
So here is my problem: without the isolator, my engine batteries read a nice 12.7 V. When turning the engine on, the voltage only increases to 14.1 V. The value is a little low I believe, and I'm also concerned because it reaches 14.1 V after 1 min, right after turning the engine on, I read 12.5, which slowly increases to 14.1. So first question, should I be worried about that?

Now when I install the isolator, I connect the alternator + to the isolator input, and batteries to the first output of the isolator. When engine off, batteries are still at 12.7 V, but when I turn the engine on, I only get 12.5V. So I checked on the alternator, and I only read 0.7 V. So it seems that the alternator is not doing its job when the isolator is installed, but I just don't understand why. Any idea? Any help would be very much appreciated.

Cheers!
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Old 04-16-2017, 08:56 PM   #2
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The diodes are starving the alternator's internal regulator of the voltage it requires to excite the alternator. You need to use an isolator with an alternator excitation provision. The best out there is the Perfect Switch battery isolator, but it's not cheap. You have a cheap battery isolator as it has a voltage drop of .7 which is terrible, and it apparently isn't the correct configuration for your alternator as there's no excitation provision.
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Old 04-18-2017, 11:38 AM   #3
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Hey guys, I'm working with the Monx on the same bus. Thanks for your help JumpShowHigh.

So basically here is how I understand the problem we have:
we have an alternator with an internal regulator, with 1 wire coming from the battery serving as an input for the internal regulator and an output for charging the battery. When we add the isolator, the current can flow only in one direction, to charge the battery, but the internal regulator don't get any current from the battery because of the isolator diode blocking it, therefore electro-magnet is not on, so no charging when engine on.

So ideally we would need a isolator with an exciter, but we dont. Could we provide the current for the internal regulator from another source? Like the ignition?
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Old 04-18-2017, 12:22 PM   #4
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Possibly, if you have a different type of regulator, but it's been my experience that that the path of least resistance is to either go to an external regulator, or change to an isolator configuration suitable for the regulator you currently have.
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Old 04-18-2017, 07:09 PM   #5
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So here is my problem: without the isolator, my engine batteries read a nice 12.7 V. When turning the engine on, the voltage only increases to 14.1 V. The value is a little low I believe, and I'm also concerned because it reaches 14.1 V after 1 min, right after turning the engine on, I read 12.5, which slowly increases to 14.1. So first question, should I be worried about that?

That part seems normal to me. The regulator takes a few seconds to determine what if any output is needed.

The next part I don't get. Have you come off the alternator positive with the wire going normally to the battery and taken it to the isolator input? If so that is right.
Then the two lower terminals are for battery A and battery B, not both batteries on the same output terminal. Then the isolator will charge both batteries through the alternator.
Hope this helps.
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Old 04-19-2017, 01:01 PM   #6
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Hey BlackJohn,

thanks for your help.
yes that's what I did. But it doesnt work, when I do what you said, the alternator doens't generate any current. It seems that it's because the alternator needs to get first current from the battery to active its electro-magnet, only then it provides currents. Therefore with the diode from the isolator, no current can reach the alternator, that's why some isolators have a 4th terminal to provide this current to the alternator.

Now, I'm trying to see how I could excite the alternator from another source, I'm not even sure it's possible.
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Old 04-19-2017, 02:21 PM   #7
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Ok so where is the power coming from for the alternator without the isolator?

Most have a separate connector to feed the exciter. Yours doesn't?
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Old 04-19-2017, 03:03 PM   #8
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theres a lot of alternators out there that are '1 wire' and have no ability to use an external Sense voltage... these self-excite at a specified RPM... many of them its as high as 1800 Alternator RPM (not engine RPM).. some of the better ones are 1200.

on my DEV bus, its a Bosch SB200 which has an external Sense and an Excite lead..
I found that if I connected the Excite lead directly to a battery, I would carry a pretty decent parasitic load because the alternator field stayed excited...

what I then did was install a relay between the battery and the excite Lead.. ( I wasnt sure if i should grab a standard Ignition feed)... once i did that then the alternator excites upon key-on, my Sense Lead is connected by Fuse directly to the Battery..

my isolator is designed to not engage the solenoid unless its detected voltage is 12.9 or higher... thus you wont kill your main batteries if you key-on without start and your house batteries are Dead. it also has a manual input on it so if I did want to involve the house batteries without engine run I can.
-Christopher
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Old 04-21-2017, 12:36 PM   #9
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Hey guys, thank you all for your help on this matter, appreciate it!

So my alternator is a Wilson SI22. It has 4 terminals, bat, negative, I and R. I just called the company, they told me that I can plug the ignition to the I terminal, which would excite the alternator and fix my problem. R is for accessories, not sure what exactly.

I'll try that and let you guys know how it went. Kind of new to this, so I'm not exactly sure how what's the proper way to find the ignition wire, probably not that hard but advises are welcome
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Old 04-21-2017, 12:58 PM   #10
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interesting, they dont have a S and I terminal.. 'S' was the Sense lead driect from battery to sense the battery..

'I' is for ignition (excites the field)...

they must get the sense from the ignition lead.. interesting..

-Christopher
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Old 04-21-2017, 01:11 PM   #11
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Let me clarify something though. As of now, only the bat and neg terminals are connected (and it works). The alternator is excited by the bat terminal and then it sends current: the "one-wire" type basically, one wire serving as input and ouput. It seems that you can excite the alternator with the I terminal as well, providing 2 ways of exciting the alternator.
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Old 04-21-2017, 01:22 PM   #12
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Have you found the ignition power wire yet?
Not sure of your bus layout electrically but you should have that wire either on the starter itself, or in the ignition switch, probably the one that is powered when the key is released to run. Likely easier to find that power source at the starter, then just run to the alternator as the company suggested.
You'll need help to test this.
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Old 04-21-2017, 02:32 PM   #13
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I'll try this weekend. I can test the wire with a voltmeter, I assume that it provides current only during the ignition so it should be easy to check if I found the right one or not.
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Old 04-21-2017, 11:05 PM   #14
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You are using the sure power battery separator, probably model 1314-200 or 1315-200, right? From what I found, that is the only 200A isolator they sell. Your issue is that sure power does not require you to wire the isolator to the alternator. It contains a relay that connects the two battery banks together when the voltage drops below 13.2 volts. It disconnects when the battery bank reaches 12.8 volts, which preserves your starting batteries after you turn the ignition off. I've drawn up a schematic for you that I hope helps. If you do have the 1315-200, it's bi-directional, which means that it doesn't matter which battery bank is on main or aux supposedly.

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Old 04-27-2017, 02:10 PM   #15
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hey tlbeck thank for your help and time.

I'm not sure about the exact model, all I have from when I bought the isolator is that it's a "Sure Power 2002 Multi Battery Isolator 200A 1 Input 2 Out". I have a terminal for the alternator that need to be connected though, I don't think it is bi-directional as in your drawing. Manual also clearly states that it has to be connected to the alternator.
One question about your diagram, why do you need the alternator R terminal to be connected to the + battery?

Regarding my previous post, I did connected the alternator I terminal (that was initially unplug when got the bus) to the ignition of the bus, took it from the starter, and it worked! The alternator turns on when engine is on now, so that's progress.

Now, I'm a little concerned, with the isolator, the atlernator only provide 12.5 V from idle engine rpm, goes up to 13.7 when rpm is around 2000. I called the constructor and they said it might be because of the batteries being in not so good condition.
So right now it seems like it works, but when engine is idle, it won't be charging my batteries much, will it?
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Old 04-27-2017, 07:04 PM   #16
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Quote:
Originally Posted by BenMaClem View Post
hey tlbeck thank for your help and time.

I'm not sure about the exact model, all I have from when I bought the isolator is that it's a "Sure Power 2002 Multi Battery Isolator 200A 1 Input 2 Out". I have a terminal for the alternator that need to be connected though, I don't think it is bi-directional as in your drawing. Manual also clearly states that it has to be connected to the alternator.
One question about your diagram, why do you need the alternator R terminal to be connected to the + battery?

Regarding my previous post, I did connected the alternator I terminal (that was initially unplug when got the bus) to the ignition of the bus, took it from the starter, and it worked! The alternator turns on when engine is on now, so that's progress.

Now, I'm a little concerned, with the isolator, the atlernator only provide 12.5 V from idle engine rpm, goes up to 13.7 when rpm is around 2000. I called the constructor and they said it might be because of the batteries being in not so good condition.
So right now it seems like it works, but when engine is idle, it won't be charging my batteries much, will it?
The R hookup on the alt is just showing that it needs 12v. It doesn't necessarily have to be the battery.

The alternator is only putting out 12.5, or was that a reading from the battery? It should be putting out around 14.4v. If that's the reading from your alternator, I would personally that it's the problem.
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Old 04-27-2017, 07:12 PM   #17
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if the second bank of batteries is dead or going bad then 12.5 volts isnt out of the wquestion for idle output.. as it is the alternator giving its all when the isolator engages.. disengage the isolator and see if the voltage goes up.. if the second isolated bank is fully charged and is good you shouldnt see that low of voltage..

14.4 is a bit high except on a cold alternator you may see that..

ifd the voltage is always low at idle and you have virtually no charge load on it.. ie youve fully charged all your batteries and have no accessories on and stil have 12.5 at idle, then its possibke one of the diodes in the alternator is bad and you get low output...
-Christopher
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Old 04-27-2017, 10:56 PM   #18
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14.4 is a good voltage for battery charging. When you start getting up into the high 14's it's not good.
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