2nd Gen Non-Engine/Transmission Seven Pin Trailer Connector??

[HBarlow]

My Ram doesn't do a good job of keeping my trailer batteries charged. Apparently the factory towing harness uses a small gauge wire back to the female connector which does not allow sufficient current flow to fully recharge the batteries if I park overnight without hookups. The towing harness also lacks a relay to isolate truck batteries when the truck is parked and the key off.



I plan to install a relay to disconnect the truck starting batteries from the trailer batteries when the key is off and also plan to run an 8 gauge wire from the relay to the seven pin connector at the rear of the truck.



Has anyone done a similar modification? Can anyone advise me how to gain access to the seven pin connector to remove the OEM wire and install a larger wire? I haven't removed the connector yet but it appears different than others I have owned. I don't want to begin by damaging the connector.



Normally, the connector can be easily disassembled to permit access to the pins where the wires are connected. I see an orange or red pin on the top which looks like it might be used to release a part of the connector????



Any information or advice will be appreciated.



Harvey

 

[klenger]

If you can't get the connector apart, you could just splice the wires a few inches from the connector. The wire that's installed can handle the current. What you are trying to do is to lower the resistance to reduce voltage drop, so a few inches of smaller wire won't affect it at all.



Here's a link to a schematic of the connector wiring.



http://www.klenger.net/dodge/trailer-connector-wiring.pdf



Be aware, that the truck will never do a great job of charging trailer batteries, but the larger wire may help.

 

[HBarlow]

Originally posted by klenger

Be aware, that the truck will never do a great job of charging trailer batteries, but the larger wire may help.

Why not? I know that some voltage drop will necessarily occur due to the long run of wire from truck alternator/batteries back to the trailer batteries, but with a larger wire I should be able to compensate for much of this drop.



Other trucks I've owned seemed to do a better job of recharging trailer batteries after overnight usage without hookups.



Harvey

 

[Ian]

Charging trailer batteries

When the truck regulator senses the truck batteries are up to full voltage, the regulator will reduce the alternator output, regardless of the state of charge of the trailer battery.

Also, if fitting a device to isolate the trailer battery from the truck batteries when the ignition is 'off', use a solenoid, an isolator will cause a small voltage drop and your trailer battery will get even less charge.

Hope this helps.

 

[HBarlow]

Re: Charging trailer batteries

Originally posted by Ian

When the truck regulator senses the truck batteries are up to full voltage, the regulator will reduce the alternator output, regardless of the state of charge of the trailer battery.

Also, if fitting a device to isolate the trailer battery from the truck batteries when the ignition is 'off', use a solenoid, an isolator will cause a small voltage drop and your trailer battery will get even less charge.

Hope this helps.

Ian,



Thanks for the explanation. If that's the case, I wonder if routing a larger charge wire would do any good after all.



I have purchased a Ford style continous-duty solenoid to isolate the truck batteries whe the key is off but in light of your explanation, maybe I should leave things as they are. It might be preferable to allow the truck batteries to discharge some as well... ... as long as I don't discharge all four batteries so far that the starting batteries lack sufficient charge to start the truck the following morning. That way, all four batteries would theoretically be charging for some time as I drive.



Your opinion on that idea?



Harvey

 

[klenger]

Fist of all, I assume that the trailer you are fefereing to is a camper and not a utility trailer where the battery is used just for the trailer brakes.



The reason the truck alternator will not properly charge a trailer battery is because the trailer battery is (or should be) a deep cycle battery, while the one in the truck is a starting battery. The alternator puts out a constant 13. 5 (approx) volts to recharge the vehicle battery. A deep cycle battery requires a charge voltate that is in excess of 14 volts to fully charge the battery. So, you have a double hit trying to charge the camper battery from the truck, 1) voltage drop in the wiring and 2) the alternator does not put out enough voltage to fully chage a deep cycle battery.



Your idea of changing the wire to a larger guage is a good one, and will help. I just wanted to point out that you still won't be able to fully charge the camper battery. For that you really need a 110 vac charger or solar panel and charge controller designed for that purpose.



Good luck

 

[HBarlow]

Originally posted by klenger





The reason the truck alternator will not properly charge a trailer battery is because the trailer battery is (or should be) a deep cycle battery, while the one in the truck is a starting battery. The alternator puts out a constant 13. 5 (approx) volts to recharge the vehicle battery. A deep cycle battery requires a charge voltage that is in excess of 14 volts to fully charge the battery. So, you have a double hit trying to charge the camper battery from the truck, 1) voltage drop in the wiring and 2) the alternator does not put out enough voltage to fully chage a deep cycle battery.

Thanks for the explanation. Yes, you're correct on both assumptions. It is a travel trailer and the batteries are deep cycle RV batteries.



I didn't know a higher charging voltage was required.



Harvey

 

[vc]

HBarlow,

I think you could use a marine multi battery isolator - I know it was mentioned that there is a slight voltage loss or something, but consider this. If you have an isolator that connects every battery - ie the two truck batteries and the wire running to the trailer - to the isolator, it wont let the alternator drop out after quick charging the truck batteries. The isolator will take the alternator charge and send it to the batteries that need charging. So even after the truck batteries have charged and the trailer batteries still need some juice, the isolator senses that and sends the demand to the alternator and keeps charging the trailer batts. Make sense? Just make sure the isolator is rated for the amps you will push through it And still change out the wire.

vc

 

[HBarlow]

Originally posted by vc

HBarlow,

I think you could use a marine multi battery isolator

I've read a little about battery isolators somewhere and I think I've seen them advertised in RV parts catalogs for use in motorhomes.



Are the isolators physically large which will present serious challenges to installation?



And, won't a battery isolator make a large drain on my wallet?



Thanks for the additional information.



Harvey

 

[Bill Stockard]

Harvey,



For more information on battery isolators and battery seperators, check this address:



http://www.surepower.com/



Bill

 

[Ian]

Solar Cell

Harvey,

I used a solenoid to disconnect the RV batteries from my '93 D250 battery when the ignition was off, worked 100%. One suggestion, buy a solenoid from an RV dealer, (about $C30) they are rated for continious duty, a starter solenoid is not. In my '93, when you turned the key to on, you could usually hear the relay engage.

Operating without some form of battery disconnect could have it's moments, expecially if you are camping some distance from services and forget to pull the 7 pin plug, flattening all the batteries. As we all know, the CTD takes a good amount of power to start, don't expect to get a boost off a Honda ATV battery.

In May of 2001 I fitted a solar cell to my trailer, the way to go. Anytime it's not dark you will get half an amp charge (75w panel, even get a little charge when parked under a street lamp in a Walmart parking lot) when the sun is shining, 3 to 4 amps. Also, the trailer lights are brighter, the cell regulator shuts down the charge at 15 volts, cuts in again when battery voltage drops to about 13. 5 volts.

 

[vc]

HBarlow,

the physical size on the isolators - I looked at one that was about 4"X5"X9" gestimate - it was a while back that I looked at it. Cost, well these said marine on it so that automatically increases price through the ceiling Looking at one catalog of marine stuff for a 130 amp rated isolator for 3 batteries it's $164. HOWEVER, I know from experience that if you look around at different companies selling the same exact product in the marine world, the price can vary drastically. By the way, another benefit of an isolator is that it wont let a "bad" battery getting low on volts suck the life out of the other good battery or batteries connected together.

vc