I have an 06 F-350 CC. I bought a new trailer last year and the other day while going over it I found the battery for the brakes to be dead. The trailer has a built in charger for the battery, but when I plug the trailer into the truck it does not show it charging.

I looked in the owners book (for the truck) and it shows a trailer brake charging circuit. The fuse panel has a fuse and a relay where the trailer brake charging should be.

I bought the truck used. It has a flat bed on it and the trailer plug-in was already wired in.

I have not done any other checks, just the fuse and relay. Not sure where to go from here or what the problem might be.

Any thoughts? Thanks in advance.
Buck

 

Remove the battery and check charge with an "old school" dumb charger. It could charge up but may take a week at a low rate to fully charge. Some chargers have self protection circuitry to prevent charging of a defective or dead battery. They simply won't trip on unless they see a certain minimum voltage, say 8 or 10 volts something like that. The charger on the trailer itself is probably not suitable for really long charging anyway. Keep the electrolyte topped off and monitor the temp-adjusted voltage charts and your voltmeter over the course of a few days and it might be OK.

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most likely the battery is in such a state that it won't accept the charge. I'd recommend a replacement.

You could also check the electrolyte level and it may need some distilled water.

 

Well it has been a while. I took the battery out of the trailer and charged it last week. It took a charge just fine and I just went out and checked it "fully charged", but I'm still having the same problem as before. When I plug the trailer up to the truck it does not show the battery charging.

Where to go now??
thanks

 

Do you have the truck running while checking to see if it is charging?

 

I just went out to double check, just to make sure I wasn't doing something stupid, yes the truck is running.

 

The battery for the trailer brake backup should be a sealed gel cell, thus there is no maintaining it.

I would check both the plug and the socket for corrosion, dirt or damage. A good clean with some electrical contact cleaner would not hurt.

You can also find a diagram, isolate the pin going to the charger and make sure the voltage output from the truck is where it should be.

 

I just went out and checked pin #5 on the truck, 12v+. Well what I got on my DVOM was 9.5-10.7 v. Not sure where I'm loosing the voltage. It is too tight under the flat bed and fuel tank to check the wiring.

I guess at this point, the brakes and lights work (trailer); I'll worry about it some other decade.

 

You could get by with charging the battery every now and then. I failed inspection on my trailer the other year because of the battery. My trailer tends to sit during the winter so I put a plug on to charge the battery with my standard 110v battery charger. This way I don't have to tear half the trailer apart to get to the battery.

 

I started messing with this again because the trailer was due for inspection. I didn't know if they would check the battery, so I pulled it all apart and charged it, just in case.

I like your plug and charger idea, I might look into that. Thanks.

 

I tow two trailers, one that only charges when the marker lights are on (feeds off marker lights despite have 7 way plug, trailer bought new...) and one that chargers from the proper pin on the 7 way.

I'd confirm which method, cause as I found out 7 way plug doesn't guarantee that the battery is actually connected to the charge line.