Charging trailer batteries while driving

[JCasper]

O. K. so I just bought a TT and am wondering, does the factory dodge tow package have a hot wire back there that charges the trailer batteries while I am driving?



Is there an isolator just in case I leave the trailer plugged in? I don't want to come out to dead batteries.



If it doesn't how do I add an isolator and where is the best place to get it?



TIA, Joe

 

[BimmerAgent]

Yup

Hi Joe- My truck, with the trailer tow package, will charge my fivers' batteries when the CTD is running. The package also prevents your trucks' batteries from being discharged by the fiver. So, no worries! Bruce

 

[TowPro]

but its an 18g wire which is pretty thin. I don't think you are going to actualy recharge a dead battery short of driving 1000 miles

 

[klenger]

I am not aware that Dodge used isolators in any of their trucks. Easiest thing to do is to unplug the trailer if you are hooked up over night. For a few hours, it doesn't matter.

 

[JCasper]

O. K. so does it charge good enough or should I upgrade it?



I can charge them at home if needed, but it would be nice to be charging going down the road.



Is the 18 Gauge wire enough to get some juice back there?

 

[Jaysyl]

I unplug if stopped for the night ,or I am going to run the generator.

 

[K5IP]

Joe,

Yes, it will get some "juice" back there, however the small wire will cause significant voltage drop, enough to limit peak current charge conditions.

# 18 will have 6. 4 ohms/1000 ft of wire. So the 15 foot run in your truck will provide about . 1 ohms of resistance between the truck charging system and connector. If your are trying to charge the battery at a 10A rate (probably not unusual), a voltage drop of 1 volt will occur. V=IR.

You can see that as a larger charge is required (depleted batteries) the larger voltage drop will increase the time it takes to charge your batteries.

Given enough time, however, they will will become nearly fully charged.

Rog

 

[Bob4x4]

O. K. so I just bought a TT and am wondering, does the factory dodge tow package have a hot wire back there that charges the trailer batteries while I am driving?



Is there an isolator just in case I leave the trailer plugged in? I don't want to come out to dead batteries.



If it doesn't how do I add an isolator and where is the best place to get it?



TIA, Joe

You have no battery isolator from Dodge. The truck and trailer batts will be connected any time your trailer connector is plugged in. The charge level will be less than optimal with the small gauge wire used,it can be upgraded. I have had my trailer batts get so low while dry camping even with my solar I will plug in to keep the reefer running.



Bob

 

[Bob4x4]

Hi Joe- My truck, with the trailer tow package, will charge my fivers' batteries when the CTD is running. The package also prevents your trucks' batteries from being discharged by the fiver. So, no worries! Bruce

Better recheck your truck,Dodge has never installed an isolator on a 3rd gen. They were available on the first gen but very rare.



Bob

 

[JCasper]

I checked with a test light last night. It is hot with the ignition on or off.



So can I disconnect the wire that's there and run another back there, say 10 gauge along with an isolator?



If so how do I go about doing it?

 

[SnoKing]

Get a constant rated solenoid WITHOUT silver contacts (you want Copper contacts). Silver contact tend to corrode and not make contact after a few years. NAPA should have one. They look like an old Ford starter solenoid. Two large leads for source/load and to small leads for the coil. Come off the drivers side battery with #8 or 10 wire and thru a 40AMP circuit breaker and then to the solenoid. Run the other side of the solenoid to the charge lead. My 2001. 5 had a heavy gauge wire already for the charge lead, which I cut at the firewall. To pick the solenoid, ground one side and find a run only switched source for the other.



As others have said, this is not the greatest way to charge the batteries, and is more like a maintenance charge. You probably can only get between 5 and 10 amps back that far.



SNOKING

 

[seemore]

O. K. so I just bought a TT and am wondering, does the factory dodge tow package have a hot wire back there that charges the trailer batteries while I am driving?



Is there an isolator just in case I leave the trailer plugged in? I don't want to come out to dead batteries.



If it doesn't how do I add an isolator and where is the best place to get it?



TIA, Joe

The best way to charge camper batteries is with a dual battery isolator. You would probably have to run a new back from the isolator, a min of 10 ga or better yet 6 or 8 gauge. Now that will charge batteries while you drive!!:-laf



Here is a link for a brand that that I've heard is good.



Hellroaring Battery Isolator/Combiner notes for Multi-Battery isolation in RV/Camper/Trailer Applications



If you contact them I've sure they will give you the proper guidance.

 

[SnoKing]

The best way to charge camper batteries is with a dual battery isolator. You would probably have to run a new back from the isolator, a min of 10 ga or better yet 6 or 8 gauge. Now that will charge batteries while you drive!!:-laf



Here is a link for a brand that that I've heard is good.



Hellroaring Battery Isolator/Combiner notes for Multi-Battery isolation in RV/Camper/Trailer Applications



If you contact them I've sure they will give you the proper guidance.

The only problem with an isolator is that you have to cut into the main charge lead from the trucks alternator. And you loose somewhere between one half volt and one volt of charging voltage that is dropped across the diodes in the isolator. Not good in my book. SNOKING

 

[TowPro]

Not sure the ford starter solenoid is rated for constent use.

Another option might be fog light relays. they can be found in the 30amp range.

Also don't forget an inline fuse, a large wire shorted out in the back with no fuse will make a lot of smoke!

 

[SnoKing]

Not sure the ford starter solenoid is rated for constent use.



Another option might be fog light relays. they can be found in the 30amp range.



Also don't forget an inline fuse, a large wire shorted out in the back with no fuse will make a lot of smoke!

You can't read! Or spell!



"Get a constant rated solenoid WITHOUT silver contacts"



SNOKING

 

[BDeMartile]

O. K. so does it charge good enough or should I upgrade it?



I can charge them at home if needed, but it would be nice to be charging going down the road.



Is the 18 Gauge wire enough to get some juice back there?

In a word yes it will charge your batteries or at least maintain them. If you have dead trailer batteries you need a long trip to recharge them also keep an eye on the 20amp fuse if you are charging dead batteries it will blow. I have also blown the fuse with the truck running and turning on the coach heater the blower draws quite a few amps. I have as yet not found a 20a circuit breaker to replace the 20a fuse.

 

[Grizzly]

Better recheck your truck,Dodge has never installed an isolator on a 3rd gen. They were available on the first gen but very rare.

Bob

Your exactly correct, also isolators were not available on 2nd gen.



JCasper, I would get an isolator and an 8 ga. wire. Be sure you get an isolator and not a cheaper ignition switch.

 

[JCasper]

Your exactly correct, also isolators were not available on 2nd gen.



JCasper, I would get an isolator and an 8 ga. wire. Be sure you get an isolator and not a cheaper ignition switch.

I will go and look for an isolator here one of these days. Now do I disconnect the factory 12v wire and run a new one?



Also does an isolator work kind of like a relay? Does it use an ignition hot source to complete the circuit and send power to the back.

 

[SnoKing]

Read my post #11 above about using a constant rated solenoid to isolate the charge lead.



I do not believe that using a diode type isolator that requires cutting the charge lead for the alternator is a good thing for a Dodge CTD given all the iffy electrical issues people have from time to time. SNOKING

 

[Ramtough]

A relay will work just as well and is a lot simpler and cheaper than an isolator. The biggest problem is that even if you get enough amperage to the pigtail, you are still going to be disappointed with your results becasue of small 12V charge converter feed wiring in the trailer. The charging service available from the truck will maintain a battery but you will not have much luch charging it. The best I have been able to do is about 8 amps on a battery that was run down around 60%.