Dual Battery Excitation wire? (1 Viewer)

Joined
Feb 28, 2008
Messages
1,390
I have a question, I am setting up dual batteries in my 1985 fj60 with a externally regulated alternator and I have the surepower 4 post 95amp isolator along with all the wires run, except the excitation wire. When I fire the vehicle up with this setup the vehicle is cleary not charging. I do not have a voltmeter at the moment but going off the dash voltmeter its defianlty not charging. Does an fj60 need to use this fourth post and if so does which of the two wires on the back of the alternator does it tie into? Thanks I really appreciate any insight.
 
Joined
Apr 1, 2007
Messages
901
Location
CT
I would try running both small wires from the alt. to your starting battery, then run the alt. output to your surepower main input. thats how i ran mine and never had a problem. The Shurepower i ran did not have the excite lug so it wasn't an option for me. However you will see a a significant voltage drop using your setup, at least i did. I ended up pulling it and using a boat switch "1,2,both,off". I realize the surepower is made for your application but it may end up killing your batteries in the long run from never letting them fully charge. Check out Hellroaring. Hope this helps.
 
Joined
Feb 28, 2008
Messages
1,390
Thanks, I called tech support at surepower and they pretty much told me the same thing that it wouldn't charge correctly because my alternator didn't have a sense wire. They were very helpful though and I think for the time being I'm going to go with one of their battery seperators until I dont need to pass emissions here anymore then swap the smog pump for a second alternator. I still wish I could figure out how to use that Isolator I just can't come with anyway to make it work. Does anyone know what the hellroaring unit does different?, or is that not possible to use on a two wire 55 amp 1985 alternator also?
 
Joined
Feb 17, 2007
Messages
888
Location
Oregon
You don't need an excite wire you with your FJ60 alternator. You can just use a regular 3 post isolator. They are quite a bit cheaper anyway, and smaller, making them easier to mount up. I had to run the 4 poster you have now, on my FJ62. Found this out after wiring in the system with a regular isolator (didn't do my homework ahead of time, just assumed :doh:) and had no charge upon start up. I have very little voltage drop with my system, less than 0.5v, and have installed many isolator systems in marine applications without problem. The switch like superjuice is using is very simple, however, only the battery that is selected on the switch will charge. So if one battery is dead, and you have to turn the switch to #2 to start, you then have to switch it back to #1 to re-charge the dead battery. If you leave it on both, the alternator can overcharge the good battery while trying to charge up the dead one.
 
Joined
Feb 28, 2008
Messages
1,390
Thanks everyone on this site is a lot of help, defiantly has saved me hours of headache. So the four post isolator dosen't work unless the excitation wire is hooked up? but a cheaper three post would do the job with only a minimul voltage drop? just out of curiosity does any one know a land cruiser alternator charges at voltage wise to start with? would the .5 still allow the batter to charge up close to the 12.7 or what ever the full charge number is. Where's a good place to pick up a three post?
 
Joined
Apr 1, 2007
Messages
901
Location
CT
A three post diode will solve one problem ie, NOT CHARGING, but won't be "PERFECT." If there was an easy way we would have found it by now. I'm gonna say ... you need to charge battery at about 14.5vdc in order to insure a full charge. That is what your stock alt. should output with one battery above 1krpm, which is above oem idle. This insures a full charge even with a full stock draw ie. lights, wipers, heat/fan,etc. Now "we" want to draw more amps/volts than can be replenished by the OEM setup. So...we resort to a second battery, now how to charge the second battery is debatable. A setup like a selenoid that conects both batteries in parallel while the engine is running is great for charging but ... if you all ready killed the secondary battery that was for winching/whatever now you ceated a tremendous draw on the alt. and main battery and depending on the inrush current could kill your starting battery. The only unit that i know of that can "divy" up the available charge by the alt. and let you choose where your power is coming from ie. A batt. B batt. or A+B batt and still keep your charging system from overloading is the Hellroaring. I am by no way affiliated with them but i do know a bit about the subject. Sorry for the long reply but there not a simple answer. cheers. oh, and remember i chose to run a marine a/b/a+b switch. I can help you with eiring if you would like. Its a bullet proof and cheap setup.
 

REKCUT

SILVER Star
Joined
Jan 5, 2005
Messages
4,673
Location
Rogersville, Mo.
Another doable option is to install a second alt. If you not worried about smog you can install a second hi output alt in place of the smog pump. You can get the alt for about $125. I run everything factory on the factory battery and alt and everything aftermarket on the second battery and alt. Both systems are independent of each other.
 
Joined
Feb 28, 2008
Messages
1,390
I really wish I could do the dual alternator setup but i'm from az and live in the valley so they are pretty hardcore about the emissions equiptment. I heard without it you get a little more power to but i did that I'd have to put it back on every other year I guess. I got a real good deal on a separator so i'll wire that up when I get it next week. I'd like to also put some manual switches in there to for safety. Super juice where did you put the switch men you went that way? man I get one thing figured out now its starting to get hot out and the a/c isn't blowing cold.
 
Joined
Mar 2, 2006
Messages
625
Location
CA
I have the same question regarding how to set up a dual battery system using a four post isolator, and am now just more confused after reading this thread. Is the moral that the four post isolator will not correctly charge my batteries? Isn't that the whole point of the thing? The instructions for the isolator say that I should be able to tap into an ignition lead going into the alternator to provide the excitation energy. It doesn't say what that excitation energy is needed (what does it accomplish?), nor which wire to tap into. Any insights on any of these fronts would be appreciated.
 

ntsqd

technerd
Joined
Apr 26, 2007
Messages
6,044
Location
Upper So. CA
Most, but not all, alternators require a voltage "signal" to start charging. A keyed ignition source usually does this function. Once spinning and excited the signal is no longer needed since the alternator will produce it's own excitation voltage. The signal just starts the ball rolling.

Apparently your 4 post also needs such a signal. My guess is that most likely there is some sort of solid state relay internal to the isolator. Without that being energized the alternator is disconnected from both batteries.
 
Joined
Feb 28, 2008
Messages
1,390
Is this on a 60? It turned out with mine I actually couldn't use the 4 post isolator. Well techinically I could but it would not charge the batteries fully and would reduce longevity considerably. So what I did was get a battery separator instead. Super easy to install Works great, had it for a while now and never left me stranted. The way it works is when your car is running and your primary batter reaches a certain voltage it connects the two batteries and charges your auxilary, when the car is off and you put a load on the aux battery it separates the aux from the main to prevent the main from running down. What Brand Isolator did you use?
 

ntsqd

technerd
Joined
Apr 26, 2007
Messages
6,044
Location
Upper So. CA
Is this on a 60? It turned out with mine I actually couldn't use the 4 post isolator. Well techinically I could but it would not charge the batteries fully and would reduce longevity considerably. So what I did was get a battery separator instead. Super easy to install Works great, had it for a while now and never left me stranted. The way it works is when your car is running and your primary batter reaches a certain voltage it connects the two batteries and charges your auxilary, when the car is off and you put a load on the aux battery it separates the aux from the main to prevent the main from running down. What Brand Isolator did you use?
Sounds like an "Automatic Charge Relay" or ACR.
CL-Series BatteryLink™ Automatic Charging Relay (Current Limiting) with Overcurrent Protection - Blue Sea Systems

I've read good things about them in the marine world and I intend to try one on my 60 once a second battery location presents itself.
 
Joined
Mar 2, 2006
Messages
625
Location
CA
Thanks guys. Yes, this is on a 60. I bought the isolator at Napa. It's a 95 amp heavy duty multi-battery isolator.

The battery separator sounds like the way to go - super simple...but I've already bought the isolator and am going to try to make that work. Kurtis, why do you say that the isolator you bought wouldn't fully charge your batteries?
 
Last edited:

ntsqd

technerd
Joined
Apr 26, 2007
Messages
6,044
Location
Upper So. CA
Diodes have what is called a "Cracking Voltage". This is the voltage required to 'open' the diode and allow current to pass and is approximately 0.5 volt. Cracking Voltage is a voltage drop, which means that if the Alt is putting out 14.5, the battery only gets 14.0 volts. Since the alt has to put out a higher voltage than the battery's current state of charge in order to charge it, this 0.5 volt loss means that the battery never gets fully charged because the alt can't go high enough to input that last little bit of charge.

In some alts the high voltage limit in the regulator can be increased to offset this voltage drop. Some of the GM late model alts need a 4 pole isolator where the 4th pole is a "Sense" pole. It allows the regulator to see what the battery voltage is without having that voltage drop in the way.
 
Joined
Aug 19, 2003
Messages
2,534
Sounds like an "Automatic Charge Relay" or ACR.
CL-Series BatteryLink™ Automatic Charging Relay (Current Limiting) with Overcurrent Protection - Blue Sea Systems

I've read good things about them in the marine world and I intend to try one on my 60 once a second battery location presents itself.

I used a BlueSea ACR in my dual batt system in my 60. Works like a charm, dash selectable, no voltage drop. Highly recommended.

2543BlueSea_ACR2LO.JPG


Mike
 
Joined
Feb 28, 2008
Messages
1,390
Mine was a surepower industry isolator and after talking to there tech support there was no possible way to use it according to there tech people. It wouldn't have been the .5 volt drop in the 60 with a surepower it would be to the point that it would ruin batteries at a very rapid pace. In fact With the excitation wire I don't believe there was even a way to trick the thing to work again according the tech there. They were really helpful and hooked me up with the separator for a great deal.
There is other brands I have heard that work that use different setups but are quite spendy compared to the seperator and the separator does the job perfectly.
 

Users who are viewing this thread

Top Bottom