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Scardey eCat 10-24-2010 04:24 PM

Charge line from car to trailer
Hi - I have a 2002 4Runner that came with a tow package. I upgraded that package to a 7-pin and _added_ an additional charge line for my new Casita travel trailer. This extra charge line cost me extra $$. Casita's directions were to have 10 gage wire for the new tow package, and 2 20-amp breakers.

Without the extra charge line, I was told that when driving, the electricity my car made would "trickle" to the trailer battery and charge it. But, _with_ the _extra_ charge line, not only would it easily charge my battery, but I'd be able to run the refrigerator while driving as well. So says Casita.

The company that installed my new tow package made a few mistakes - put in a 12 gage wire, put in 2 30 amps...they now have 2 20 amps in there, but still have the 12 gage wire. They say it is impossible to run both, and that the _extra charge line_ they installed for extra $$ is a "trickle" line.

So, why pay extra? I am confused.

Now I am getting conflicting information from each.

What do I need to do to be able to charge my trailer battery AND run my refrigerator (Dometic brand, draws 15.5 amps) when driving and pulling the trailer?

Any information would be really helpful. Thanks.

Speedy Petey 10-24-2010 05:32 PM

This is more of a question for an automotive forum, but may of us do have experience in this.

From my experience, not all 7-way wiring harnesses have the "charge" terminal activated.
The "charge" line in a 7-way connector is just that, a battery charge. I have never know it to be heavy enough to run an appliance directly. I don't know who told you you would have TWO direct feed lines, or charge lines. There are simply not enough terminals in the connector for it.

Speedy Petey 10-24-2010 05:35 PM

Does the trailer have brakes? Maybe they were going to rig the brake terminal to be an extra charge line?
IMO this would be a complete hack job.

frenchelectrican 10-24-2010 06:36 PM


Originally Posted by Speedy Petey (Post 522394)
Does the trailer have brakes? Maybe they were going to rig the brake terminal to be an extra charge line?
IMO this would be a complete hack job.

I agree with Speedy Pete and if that the case this is is complety dangerous.

With charge line there will be a relay in the engine bay area so when you have key on it will start chargeing the trailer battery only when the key is on when you turn the key off it will shut off to prevent battery draindown and of course it should be a fuse in there as well IIRC it will be anywhere from 20 to 50 amp fuse depending on what model { 30 amp is most common one }

4.0mm˛ { 12 AWG } conductor useally good about 15 to 20 amp depending on which type of conductor itself so there are more than just basic issue to address.

If there is a way to attached a photo one of us will able indentify it in correct manner.

Normally the 7 way connector used in North Americia side will have ground { white } taillights { brown } Left turn / brake { yellow } Right turn / brake { green } Electrique brakes { bleu } Aux or battery charge { red or black } and aux for other { other colours as needed}( note not all the colours will be consist so please double check with your Vechile and trailer connection due some variations of connection colours and function )

Here the photo .,


Scardey eCat 10-24-2010 08:22 PM

charge line on a 7-pin
Yes the trailer has brakes and that is why the 7-pin was needed. The 4Runner originally came with a 4-pin set up.

I was told, and I paid extra, for a "charge line".

Without this "charge line" would the 7-pin set up do more than the lights and brakes? Is this the "trickle charge" line they talk about that very slowly charges the battery when you drive or have the car on?

Where would they have installed the "charge line" in the diagram you provided?

Would you know if it needed 10 or 12 gage wiring? Yes, I will call an automotive shop for more information as well.

This is very helpful to tease apart and I thank both of you.

Speedy Petey 10-24-2010 09:10 PM

Actually, since the vehicle was not factory wired with a 7-way the center pin can be used for an added aux if backup lights are not used.
Maybe they wired this as a heavier +12v source?

All trucks I own and have owned have had the center pin wired for back-up lights.

Scardey eCat 10-24-2010 10:25 PM

Charge line from car to trailer
Yes, I do NOT have back up lights that work on the trailer. I thought it was because the 4Runner did not allow for that (I think I read that or was told that).

So, if they used that slot for the charge line, I am still unclear how that works. Does it simply trickle charge the trailer battery when the 4Runner battery is on? Or does it charge the trailer battery much more strongly and quickly? Or does it do all that and it can still run the refrigerator (15.5 amps) when driving?

What do you think?


frenchelectrican 10-24-2010 10:38 PM

The biggest issue you will have is ground circuit espcally on the trailer connector due you will have lights ., brake load { with electrique brakes } , charging circuit or hot 12 volt source so it can get over 30 amp pretty easy espcally when the electique brake kick on.

Some pepoles slove that issue by putting a Anderson plug which it is a super hevey duy plug which it can take alot more current than the standard 7 way RV connector can handle otherwise a Commercal 7 way connector have beefier connections however they are not flat blade they are round pin so they can take a bit of abuse there.

(For my set up the centre pin is the straight brake lights so that way I have seperated turn lights there.)


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