Charging trailer batteries

[float5]

A couple of questions:

If parked at storage (or a campground), can the trailer batteries be charged without the brake controller in place, as in, don't have it with you? Just hook up the 7-pin.

If parked on a trip with trailer hooked up and stop for lunch, do we know that the trailer is using the TV battery, or is that vehicle-specific? We have almost never unhooked the 7-pin and never had a problem.

[Kountrykamper]

Originally Posted by float5

A couple of questions:

If parked at storage (or a campground), can the trailer batteries be charged without the brake controller in place, as in, don't have it with you? Just hook up the 7-pin.

If parked on a trip with trailer hooked up and stop for lunch, do we know that the trailer is using the TV battery, or is that vehicle-specific? We have almost never unhooked the 7-pin and never had a problem

.

Brake controller has nothing to do with charging. On a 4Runner there should be a isolation relay and it will not charge unless the vehicle is running.

The same relay will not allow you to use the TV battery unless the TV is running and you would probably not have a problem unless you are running the fridge on 12 volt.

[Brian B-P]

The battery charge line from the tug operates independently of the brake line, so it doesn't matter whether there is a controller installed or not.

Whether the tug's battery remains connected to the trailer when the tug is not running is vehicle-specific. In my opinion the connection should be turned off either when the engine is not running, or when the voltage from the tug is below a cut-off threshold... but not everyone agrees, so I suggest checking your 4Runner's towing receptacle (with the ignition off and no trailer plugged in) to see if there is power - hopefully and probably not.

[float5]

Just wanted to make sure that not having the controller in did not possibly affect something the wrong way. Good.

Thank you both.

[C&G in FL]

Originally Posted by Brian B-P

The battery charge line from the tug operates independently of the brake line, so it doesn't matter whether there is a controller installed or not.

Whether the tug's battery remains connected to the trailer when the tug is not running is vehicle-specific. In my opinion the connection should be turned off either when the engine is not running, or when the voltage from the tug is below a cut-off threshold... but not everyone agrees, so I suggest checking your 4Runner's towing receptacle (with the ignition off and no trailer plugged in) to see if there is power - hopefully and probably not.

I would do as Brian suggests......check to see if there is still power with the ignition switched off. But I would check it a few times at varying intervals. My F150 12v feed is live immediately after turning off the ignition and it stays live, but only for a short period of time. If I am making an overnight stop and I am not unhitching, I typically leave the umbilical plugged in because once it shuts down, the trailer cannot drain the tow vehicle's batteries.

[Donna D.]

Wiring seems to have some sort of "shelf life." Covering gets brittle, abrasion happens. When I tow my 28 year old Scamp, I always disconnect the umbilical. Grounds happen! I now have a "new" tug and a "new" trailer. Disconnecting (even overnight) doesn't seem so critical. The "old" trailer with "old" wiring.. yeah. Figuring out why the ignition key doesn't turn on the tug is a bigger PITA than just disconnecting the umbilical. YMMV

[cpaharley2008]

Since my Ram does not turn off, I installed both a spare 7 way as well as a plug cover on my box, one for protection when disconnected and the other for turning on the trailer lights at night when stopped at a rest area, either way I am disconnected and there is no drain on the tow battery.

[float5]

Tried to charge the trailer batteries with the TV. Nothing happening. Did this a few weeks ago with no problem. We have removed the solar monitor connections but that is all. Don't think it would need to be connected, right?

[padlin]

Cathy, how did you determine nothing was happening?

[float5]

Originally Posted by padlin

Cathy, how did you determine nothing was happening?

Ran the car hooked up for some time using the same tester to see the result. Previously went up significantly in a few minutes. This time, no increase, actually down a little.

[Iowa Dave]

On your battery on your tow vehicle there has to be a hot wire going back to the seven pin. This would charge your Escape battery when going down the road. On my Highlander this wire is equipped with an inline 40 amp fuse. It is not factory. This hot wire got accidently shorted. The fuse blew. I was loosing Escape battery power ( less amps) when out west last summer. I put in a new fuse. Batteries in Escape started charging again. See if you have a fuse and power going back to the seven pin. That's all I got.
Dave

[float5]

Don't know where the fuses are. Actually I realized that I bought a new car battery in the intervening time. Wonder if that needs something to do with charging the trailer.

[Iowa Dave]

Check the positive terminal on the battery. . Is there a smaller wire attached in addition to the big thick one? Does it look factory or aftermarket. Is there a fuse holder that pulls apart? It should be about an inch square and 3/8 inch thick. Mine has a Maxi blade fuse. 40 amp. Pull it apart if you have one and look at the fuse. Replace if in doubt. About $4. Auto zone etc.
Dave

[Brian B-P]

Before connecting to a charging source, the trailer's battery will be at something less than 13 volts. When a working charging source is connected, it will rise to something above 13 volts... and when the charging source is disconnected the trailer battery voltage it will go back down to under 13 volts (but higher than before charging). You don't need a long time to check this - just a voltage reading in the trailer (and not just the lights common on tank level displays).

Originally Posted by float5

Actually I realized that I bought a new car battery in the intervening time. Wonder if that needs something to do with charging the trailer.

It could... if the trailer charge line comes directly from the battery positive terminal, and if the person who changed the battery removed this connection and didn't replace it.

[alanmalk]

Originally Posted by float5

Don't know where the fuses are. Actually I realized that I bought a new car battery in the intervening time. Wonder if that needs something to do with charging the trailer.

You could do a sanity check to see if there is power going to the 7-pin connector on your tow. With the engine running there should be roughly 14 volts between pin 1 and 4 on the connector sockets. If you google "7-pin trailer wiring diagram" you can see what the complete pin assignments are.

--
Alan

[float5]

Originally Posted by Brian B-P

Before connecting to a charging source, the trailer's battery will be at something less than 13 volts. When a working charging source is connected, it will rise to something above 13 volts... and when the charging source is disconnected the trailer battery voltage it will go back down to under 13 volts (but higher than before charging). You don't need a long time to check this - just a voltage reading in the trailer (and not just the lights common on tank level displays).


It could... if the trailer charge line comes directly from the battery positive terminal, and if the person who changed the battery removed this connection and didn't replace it.

I can believe that the connection was removed. That would certainly account for it. I will look for a loose wire!

Yes, when I charged the batteries before, they were well below 13 and went up to 13 or 13.1 in a few minutes. Then, of course, back down to maybe 12.65 in not long. Which is what I would expect. No such thing this time. I use a 12-volt tester. I don't even think to ever look at the battery monitor with tanks. Thank you!

[float5]

Here is the battery.

[float5]

Don't know if anything is not right.

[float5]

Another

[float5]

Photo battery