2nd Gen Non-Engine/Transmission Trailer battery isolated?

[bighornram]

I am a proud owner of a 2002 HO 6-speed and new to TDR. The truck has the camper and tow packages. When I purchased the truck my Dodge dealer installed an isolator unit and third battery under my bed for an in-the-bed camper. I was told that it was also connected to the trailer connection on the back of the truck. I purchased a fifth wheel camper in June. The camper dealer installed the hitch, trailer brake, and wired to camper to the truck. They put a connection in the wall of the bed which is connected directly to the trailer harness. They told me the battery under the bed (installed by the Dodge dealer) is also wired to the trailer harness. Effectively now I have the camper battery under the bed charging (connected) with the 2 batteries under the hood when the truck is running, and isolated from the truck batteries when the truck is off. With the addition of the 2 batteries in the fifth wheel, when the fifth wheel is connected to the truck (trailer connection), the under bed isolated battery is connected with fifth wheel only when off, then all five batteries are connected when ignition is on.



whew! :--)

I spoke with a service tech this morning with the camping dealer. He is telling me that the RAM's tow package has it's own isolating system and the trailer harness is isolated from the truck batteries when the truck is off (from the factory). If this is true I don't need the isolator wired into the truck's system. To top it all off, I pulled my trailer this week about 500 miles. When I started the fifth wheel had been unplugged for a couple weeks, generally it takes about 3-4 weeks to loose enough battery to cause the CO/propane detector to alarm (beep) low battery warning, so I was not fully charged. When I arrived the battery indicator in the fifth wheel said I was only half charged. I am thinking after some 9-10 hours charging on the truck they should have been fully charged. Maybe the truck isn't charging the trailer batteries/bed battery correctly. I am wondering at this point if I should just remove the isolator unit installed at the Dodge dealer IF the truck already will isolate the trailer.



So I am really asking if anyone knows if it is true that the tow package isolates the trailer from the truck. Suggestions would also be great!

 

[Thomas]

... So I am really asking if anyone knows if it is true that the tow package isolates the trailer from the truck...

It is not true.

 

[Rman]

I concur. My camper has a isolator to keep the camper batteries seperate from the truck system. To my knowledge the tow package has no isolator that I;ve ever found (I did all my wiring)

 

[SnoKing]

Due to the lenght of the wires going back to the trailer, it is hard to get very many amps back there to charge the batteries. If I was you, I would remove the battery under the truck. If you parallel batteries they should all be the same make, model and age. Also the cable lenght should be equal. New batteries will take on the charteristics of the weakest paralleled battery in short order.

http://bart.ccis.com/home/mnemeth/12volt/12volt.htm Spend some time reading at this site.



I added a constant rated solenoid under the hood that is pulled up when running to isolate my trailer when stopped. SNOKING

 

[WBusa]

In my '95 the tow package does not isolate. The breakaway battery in my horse-trailer has a test circuit in it... and I've learned through cruel experience that if I test it while the trailer is connected (electrically) to the truck, I'm actually testing the truck's batteries (this happens whether truck is on or off).

 

[gbm]

JWolf,

Like the others have said, there is no factory isolation in your camper charging circuit.



To minimize the chance of being stranded, you really need an isolation system. To achieve proper charging of the “house batteries”, you need a quality isolation system.

Quality cable of sufficient size, quality cable connections, good batteries, sufficiently strong truck alternator, and a quality isolator.



The good news is that your stock truck alternator should provide the power you need – if it is good working condition.



You have lots of choices for an isolator. You can use a manual switch – like a Perko switch used in boats and some RV’s. You can use a relay type isolator. You could use a diode type isolator. Or, you could use a “sensing” relay isolator. It would take me several pages to explain why a sensing relay system is the best way to go. Here is a link to a company called Hellroaring. They make the best sensing isolator I could find.



http://www.hellroaring.com/



I wish someone had shared this with me before I started my project, I would have saved numerous headaches and lots of wasted money. When people say “do it right, it will save you money and aggravation” this is the company they mean when you are talking about charging isolated batteries.



The Hellroaring site will explain why your house batteries will never properly charge if your current isolator is a diode type.



Hope this helps,

Geoff

 

[Joe G.]

I rigged mine so that the wire to the trailer connection is on a relay. If the truck ignition key is not in the R position there is no connection to the trailer.

 

[WestTN]

The diode type isolators will cause a 0. 7 volt drop in the system. They will only charge both systems equally if the alternator output is connected directly to the isolator input and then the truck system is connected to one output and the camper/trailer system is connected to the other output. Your dealer probably just ran the trailer feed through the isolator if it is under the bed. That would mean you have 0. 7 volts less going to those systems. Add a long wire and the voltage drops further according to the load. On a typical summer day you will get 13. 8 volts to the truck batteries and no more than 13. 1 to the camper/trailer. That would never top the batteries up.

 

[RWhites]

I have used a "Hobb's" brand oil pressure switch to control a 100% duty cycle relay to parallel battery systems and had great success.



Installing an isolator diode will reduce the charging voltage to the battery by . 6 volts, which is a bad thing. If you have the "Diode" style isolator get out your meter and check the voltage drop.



The one extra part you should add is a marine battery switch so you can enable, block or bypass the parallel in case of trouble. I have installed many of these types of systems on boats for protecting the starting batteries from discharge as the house the batteries go down. The oil pressure switch won't make parallel untill engine starts and reaches whatever pressure threshold the switch is designed for.



System voltage vs the resistance of the circuit (connections,cables,wire lenght, batteries internal resistance) will determine where the current flows. This means short large cables will "hog" the current. The camper battery will not reach full charge very rapidly due to long cable lenghts and additional connections.



It will work but perfection is hard to obtain.





Rich

 

[PKleine]

JW,



If you use an isolator such as the one offered by Hellroaring Technologies you will see less than 0. 005 volt loss across it. That is rather insignificant compared to the losses due to the length of the wires involved. I suggest you consider upgrading the charge wire to 8 gauge if you are looking to flow any significant current back to the trailer.



I'm not affiliated with Hellroaring Technologies, but I've been using one extensively without incident.



PK

 

[bighornram]

Thanks for the great response to this thread!!



I got the volt meter out and checked my truck. The truck batteries, and truck terminal of the isolator, AND the + terminal on my trailer harness read 12. 63 VDC. The harness from the auxiliary battery (under the bed) and the auxiliary battery terminal on the isolator both read 12. 90 VDC. Further tracing the wires from the isolator, it is wired separately from the trailer harness. + wire comes from the terminal inside the fusebox. It is fused from the alternator by the main fuse in the box. The RV dealer recommended that I ADD a larger guage wire to the isolator and run it to the back of the truck and replace the + wire in the harness at the connection at the back of the truck. The isolator will isolate both the trailer harness and the auxillary battery under the bed. This could be a temporary fix since the solenoid type isolator is already in the truck. I read about the isolators at Hellroaring. Sounds sweet. They mention using 2 isolators on a diesel???

 

[PKleine]

I got the volt meter out and checked my truck. The truck batteries, and truck terminal of the isolator, AND the + terminal on my trailer harness read 12. 63 VDC. The harness from the auxiliary battery (under the bed) and the auxiliary battery terminal on the isolator both read 12. 90 VDC.

Are those voltages with the engine off?

I read about the isolators at Hellroaring. Sounds sweet. They mention using 2 isolators on a diesel???

That all depends on what you are trying to accomplish with the isolators. For most situations, like yours, you only need to use one isolator. Most of the time all we are trying to do is prevent the camper/trailer from discharging the trucks starting battery. The Hellroaring isolator prevents the camper/trailer from discharging the truck battery until the alternator is putting out.

 

[bighornram]

Those were with the engine off, in the morning. It was cold out. After driving the truck a couple hours, got home turned truck off, was off for about 15 minutes. Went out and restarted engine and got 14. 4 VDC with truck running at the harness.

 

[bighornram]

I replaced the + wire in the trailer harness with 8-guage from the present isolator (soleniod type). Will probably replace with an isolator from Hellroaring Technologies but right now this isolator is working ok and I want guages and a 4 inch exhaust first. I am getting 14. 6 VDC at the bumper with the truck running.

 

[RWhites]

14. 6 volts at the trailer harness connector is good BUT with no current flow the voltage drops will not show. Put a load on the system and check again.

Try plugging in your trailer, turn on the 12v reefer and start the engine. Check the voltage across the alternator to ground, across the battery, across the campers DC mains ect. You will find the voltage drop will be larger as more current flows and the distance gets longer. Thats when big wire pays off.

Rich