# trailer/battery/charging/inverter???



## Bone Saw (Feb 13, 2006)

mabey some electrician/trailer wiring gurus can help me out here. Right now I have a wells cargo trailer with 7 pin plug, with brakes, no dot breakaway kit. The interior lights(2) goto a wall switch, which only go on when I have my headlights on. I want to install a deep cycle battery (for interior lights and small inverter for charging tool batteries), that charges from vehicle when hooked up. What would be the best way to do this from the electrical access panel??? I will try to post a factory schematic. TIA:thumbsup:


----------



## Dustball (Jul 7, 2006)

Wire the center pin of the vehicle connector to a battery isolator. 










The center pin of your trailer connector would then go to your trailer battery.


This is taken from www.smithae.com/rv.html



> DC Battery Charging, Engine and Coach
> Let's talk about recharging the battery system while you're traveling. An important point is that the batteries must be isolated from one another. If you decide to connect the two batteries together without some way of isolating them, you must use large battery cable or you may overheat the wiring when the engine starter tries to pull current from the coach battery during starting. You also run the danger of running both batteries too low to start the engine while you are parked. This could be a serious problem if you are dry camping miles from no where. Some RV's have a dual battery switch that allows you to connect the batteries together. Don't leave this switch in the dual position, unless you are sure it is control by the ignition switch! The better of these systems use a time delay to allow the engine battery charge to stabilize before closing the circuit to the coach battery via a solenoid. The best systems use a Dual Battery Isolator to solve this problem. The isolator allows each battery to be charged by the engine alternator, but does not allow a drain from one battery to the other. This is important if you are dry camping. Some RV's will also have a solenoid with a momentary switch in the event that you need to start your generator on a low RV battery or boast your engine battery during starting. I would only rely on this in emergencies, thus avoiding current surges between the two batteries, one of which may be fully charged and the other low. If possible, it is better to start your engine and let the alternator charge the system a little first. It is also a good idea to have a circuit breaker installed in the circuit between the isolator and the RV battery to avoid overworking the alternator and wiring. Now you understand how the engine alternator keeps both batteries maintained, but what happens when you stop driving and start camping? We will cover this next.


----------



## Bone Saw (Feb 13, 2006)

thanx dust, let me clarify a little, 
under the factory electircal panel cover, everything is wire nutted together, 

On the trailer end: if I connect the white to batt- and black to batt+ should everything function as I would like, or is there more to it, can I just ground the - on the batt or should it be connected to the white, should it go through fused terminal blocks or just wire nutted in?


on the vehicle: I already have an auxilliary deepcycle battery for an inverter with an isolator, can I use existing isolator for both vehicle auxillary battery and trailer auxillary battery, a little confused here, I plan on never drawing off of vehicle while not in tow. again tia:thumbsup:


----------



## Dustball (Jul 7, 2006)

Bone Saw said:


> thanx dust, let me clarify a little,
> under the factory electircal panel cover, everything is wire nutted together,
> 
> On the trailer end: if I connect the white to batt- and black to batt+ should everything function as I would like, or is there more to it, can I just ground the - on the batt or should it be connected to the white, should it go through fused terminal blocks or just wire nutted in?
> ...



Trailer end- your trailer battery positive should be connected to whatever pin that is being fed from your tow vehicle, most likely the center pin. On my trailer, I have the battery ground as well as all the trailer light grounds directly tied into the ground pin on the connector. I don't rely on the coupler/chains to provide the ground path.

Your vehicle- if I'm right, you're saying you already have two batteries and you want to add a third one to the system. If so, you'll need an isolator that can handle three batteries such as the BIC-75300/95300 here- http://www.hellroaring.com/bic75300.php Hellroaring has a good reputation.

Your third option is to simply have the trailer battery independent of the vehicle meaning you'd charge the battery as needed using a battery charger.


----------



## Robie (Feb 25, 2005)

So, from what I'm reading here, my Dodge Ram 2500 with trailer towing package, isn't sufficient to charge 2 deep cell batteries on board the trailer when hooked up?
I have a _converter _which I bought to charge everything when plugged into A.C, but was under the impression I would be okay charging the trailer batteries while driving.
No??


----------



## Bone Saw (Feb 13, 2006)

Dustball said:


> I have the battery ground as well as all the trailer light grounds directly tied into the ground pin on the connector. I don't rely on the coupler/chains to provide the ground path..


ditto, the ground wire also ties into the frame near the axles for the brakes on mine, I agree on the no no with relying on coupler/chain. I was reffering to tying the batt- to the frame as well, or would there be too much resistance?



Dustball said:


> Your vehicle- if I'm right, you're saying you already have two batteries and you want to add a third one to the system. If so, you'll need an isolator that can handle three batteries such as the BIC-75300/95300 here- http://www.hellroaring.com/bic75300.php Hellroaring has a good reputation.


bingo thanx:thumbsup:I learned something today, will this one replace my existing one? I'll admitt I'm alittle electrically challanged when it comes to connections, wire gauge, resistance etc, I don't want to create an electrical fire


----------



## Dustball (Jul 7, 2006)

Robie said:


> So, from what I'm reading here, my Dodge Ram 2500 with trailer towing package, isn't sufficient to charge 2 deep cell batteries on board the trailer when hooked up?
> I have a _converter _which I bought to charge everything when plugged into A.C, but was under the impression I would be okay charging the trailer batteries while driving.
> No??


The issue with not using a battery isolator with multiple batteries is one battery will always try to draw from another. Say you park your truck and trailer for the weekend and you accidentally leave something on in the trailer and didn't know about it. You risk drawing down the vehicle battery to the point where it can't start the vehicle. A battery isolator prevents this from happening.

If all of the batteries are not the same age and size, you will run into the issue of one battery discharging another without an isolator.

All that said- I don't have an isolator. I keep my trailer battery separate from my truck. I use my battery charger as needed to keep it fresh.

Bonesaw- I just had a chance to look at your diagrams posted above. It looks like pin 4 on the trailer end is for your lighting circuits. Now it just depends on the vehicle and if it's #4 pin is the same. I know on my truck it isn't- #4 is used for reverse lights.


----------



## A_and_E_Auto (Nov 27, 2007)

Bone Saw, What kind of vehicle do you have?

Robie, What year is your Dodge Ram 2500?


----------



## Robie (Feb 25, 2005)

The Ram is a 2004. It has the trailer package, snow plow package...


----------



## Bone Saw (Feb 13, 2006)

05 sprinter 2500 with factory tow package and brake controller


----------



## ctiautomation (Mar 18, 2009)

Bone Saw said:


> thanx dust, let me clarify a little,
> under the factory electircal panel cover, everything is wire nutted together,
> 
> On the trailer end: if I connect the white to batt- and black to batt+ should everything function as I would like, or is there more to it, can I just ground the - on the batt or should it be connected to the white, should it go through fused terminal blocks or just wire nutted in?
> ...


It's always safer to go thru a fused terminal block
http://www.clrwtr.com/ABB-Entrelec-Terminal-Blocks.htm
http://www.clrwtr.com/Weidmuller-Terminals-Terminal-Blocks.htm
http://www.ctiautomation.net/Marathon-Terminal-Blocks.htm


----------

