The RVers Corner

by **Carl** » Mon Sep 19, 2005 5:42 pm

Well, I got my isolator from JC Whitney and all the wires to hook up the charge line for my TT. The instructions that came with it are really not very good. I have a 1995 F150, can anyone tell me if I have to cut the wires on my alternator plug to hook this thing up. Or just splice into them? The isolator has three leads on it. Center for Alt, Left for Aux Battery and the other for main battery? Does anyone have a diagram they can send. I really hate to cut into the wires on my Ford without having a good idea which ones to cut. Carl

by **Bob Boucher, Ontario!** » Mon Sep 19, 2005 5:58 pm

Carl:

I may be wrong, not a Ford man, but you should have a lead from the alternator to your truck battery!

You disconect this lead at the battery, take it to your isolator's alternator terminal (center), run a new lead from the (right) main batterie terminal and lastly a second lead to your aux battery from the left terminal.

See if that makes sense and jive with their limited instructions!

Bob :roll:

by **Carl** » Mon Sep 19, 2005 6:04 pm

Thanks Bob. That means I will have to disconnect and cut the wires at the plug going into the alternator? This thing must be made in China or Tiwan because I can't even read the instruction. Carl

by **Marty in TN** » Mon Sep 19, 2005 6:43 pm

Carl my opinion: Do not cut the wire at the alternator. Bad choice. If it were me, I'd run a heavy duty wire from Truck battery through a fuse to the center point or to the "in point" of the isolator and then one wire back to the TT battery. I wouldn't even worry about the other side, put a cap over the terminals to keep them from shorting out the system. This way, the alternator will always keep the truck battery charged when running and let the TT battery be a slave to the rest of the system. By the same token, the TT battery will not run the truck battery down. Secondly, if in the future you wish to put a charger on the TT battery, the isolator will isolate the truck battery from the charger or to put the charger on the truck battery and it'll charge up the TT battery at the same time in the same manner as if the truck alternator was running. I would also put some type of a switch between the truck battery to the isolator to keep the wire back to the TT plug open when not hooked to the TT.

Like I say, just my opinion-

Marty

by **Thomas Thibodeau** » Mon Sep 19, 2005 10:38 pm

If it were me, I'd run a heavy duty wire from Truck battery through a fuse to the center point or to the "in point" of the isolator and then one wire back to the TT battery.

I would not do this if you have a solid-state isolator.
You would only be installing a diode in that line. If the TT is left connected to the truck at any time without the engine running and you have something on in the TT as soon as the TT battery has a voltage .3 to .7 volts below the truck battery you will start drawing from the truck.

Also the TT battery will be charged at a lower rate.

Thomas

by **Marty in TN** » Tue Sep 20, 2005 1:30 am

Thomas, you have a very good point. Guess I'll have to double clutch my thinking on this one. However, to me, that truck battery is more important then the TT battery. That's why I would never cut the wire from the alternator to the truck battery.

Marty

by **Bob Boucher, Ontario!** » Tue Sep 20, 2005 11:54 am

Interesting!

:idea:

I always tought the purpose of an "isolator" was just that, isolate the truck battery from any house draw?

The line from the alternator to the isolator is not really "cut", it is re-routed and spliced at the isolator! The alternator and truck battery remain on the "live" side of the isolator. The house battery is on the protected side of the isolator thus disallowing any house battery draw on the truck battery!

This is how an autoelectric shop tech in Alabama explained it to me when my isolator had to be replaced.

Did I get it wrong?

Bob :roll:

by **Bob Boucher, Ontario!** » Tue Sep 20, 2005 11:59 am

Carl:

Try going to www.bcae1.com/battiso.htm

Good clear diagram there! Got it through Google on a "Battery Isolator" search!

Bob :wink:

by **Mickey** » Tue Sep 20, 2005 3:27 pm

Bob Boucher, Ontario! wrote:Interesting!

I always tought the purpose of an "isolator" was just that, isolate the truck battery from any house draw?

The line from the alternator to the isolator is not really "cut", it is re-routed and spliced at the isolator! The alternator and truck battery remain on the "live" side of the isolator. The house battery is on the protected side of the isolator thus disallowing any house battery draw on the truck battery!

Did I get it wrong?

Bob

I'm with you Bob.

One thing breezed over slightly is the voltage drop across the diodes in these isolators. When added into the voltage drop for the LONG wire back to the trailer you're talking a lot of drop and very possibly limiting the charge current to ver few AMPS. I personally perfer the selenoid type isolation. Theoretically there is no voltage drop across these. They can be wire so they actuated when the ign switch is on or can be wired using a switch so you can control when you wish to having the trailer being charged. Would also give serious thought to running some heavy wire (8-10 ga) back to the trailer to min voltage drop and improve charge current.

by **Carl** » Fri Sep 23, 2005 7:03 pm

Bob Boucher, Ontario! wrote:Carl:

Try going to www.bcae1.com/battiso.htm

Good clear diagram there! Got it through Google on a "Battery Isolator" search!

Bob

Thanks Bob. Good site. The kit I bought from JC Whitney is the diode type. It came with everything I need to hook it up. The directions are not that good, the company who made the isolator is supposed to send me some new directions for it. Carl

by **Carl** » Fri Sep 23, 2005 7:07 pm

Bob Boucher, Ontario! wrote:Interesting!

I always tought the purpose of an "isolator" was just that, isolate the truck battery from any house draw?

The line from the alternator to the isolator is not really "cut", it is re-routed and spliced at the isolator! The alternator and truck battery remain on the "live" side of the isolator. The house battery is on the protected side of the isolator thus disallowing any house battery draw on the truck battery!

This is how an autoelectric shop tech in Alabama explained it to me when my isolator had to be replaced.

Did I get it wrong?

Bob

Bob, this is the way I plan to hook it up, Just not quite sure which wire I splice from alternator. Mine has a plug in with three wires coming out of it. Guess it is time to open up the old Ford shop manuals before I do anything else. Carl

by **Rich** » Sat Sep 24, 2005 2:31 am

Carl you should have two heavy wires and one light wire in the alternator plug if you fallow the two heavy wires back you should find that the tie into one wire that ends up at your truck battery and it has a fusible link at the end you need to cut that wire from the alternator and attach it to the center post on the isolator and then run a wire to the truck brattier and then one two the spare battery and then run a ground cable from the spare battier to complete the circuit.

by **Les Doll** » Sat Sep 24, 2005 7:00 am

Ummm ...

If I may say something here ...

We wire tow vehicles everyday, we do this for a living, our shop does about 5 a week ... I have been installing tow vehicle wiring for 10 years and I have not installed a diode based isolator for 8 years.

Why?

Because the new way works better.

Why?

Because a $20 electro-mechanical relay or a $7 electronic relay replaces that isolator with fewer connections and less headaches for the service department.

Why pay $60 to $100 or more for an isolator ... a relay will do the same thing at a fraction of the cost.

by **Rich** » Sat Sep 24, 2005 12:01 pm

Les we were using a constant duty 12 volt solenoid 30 years ago to wire a dual battery system much cheaper and if it went bad you could go to any parts store and get a replacement. :lol:

by **Carl** » Sat Sep 24, 2005 3:30 pm

Too late. I should have asked here before buying the isolator. Now that I have it, I need to hook it up that is why I asked the dumb question. I guess I could ask JC whitney to take this back and then buy the other style. The reason I bought the one I have now is it is like the one on my brother's boat that has worked for years without a problem. Les, I value your input, advise and that is the reason I am on this forum, now if you will be kind enough to give me an example of the isolator you are talking about, I will do a search and see if I can find it. My main reason for even putting in an isolator is to keep the truck battery from discharging when the trailer battery discharges. I could just run a line from one battery to the other and unplug whenever I set up. I was told that an isolator is the safer way to go. :oops:

Carl

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