Why is my battery not recharging when towing?

[drrob]

Just bought a really nice 2000 Safari 25C. Battery is not recharging during towing. What might be wrong or am I doing something wrong?

[n2916s]

Probably is charging, just very slowly. It is a long run of wire and there probably isn't a whole lot of spare amperage available to begin with.

Mike

[dznf0g]

First trailer on your vehicle? What vehicle do you have?

[silverlabs]

What type vehicle do you have? If a F150, you need to make sure the relay is added. Up to the 2015 model, most required a relay an another fuse to be installed to allow the charging to take place. They were normally in a plastic bag in glove boxes and just need to be plugged into the fuse box. Can't remember off hand the actual number in the box as on the road with my 2015 and it has a different setup. My 2011 is in TX. Just a thought.

[AWCHIEF]

What are you towing with? Some auto alternators only out enough for the TV systems with little reserve. You might have to go with a larger alternator. Back in my racer days we used to use the Corvette alternators as they had a much higher output than most others.

[KJRitchie]

Take a multimeter and check the voltage at the 7 pin connector. If you are not getting voltage on that pin the the truck is the problem. If you are getting voltage then check the voltage of the batteries at the posts. Plug in the trailer connector and start the truck. Check the voltage on the battery posts again. There should be a rise in the voltage with the truck running. If you see no rise then there is a disconnect within the trailer. Trace the black wire from the harness to see wher eit terminates in the trailer. Check voltage there. it should be connected to a positive bus bar.

Kelvin

[drrob]

I am towing with a 1998 Chevy conversion van with 5.7L. I get a red light on 7pin that shows positive connection but I will get a volt meter and check though automotive is not my forte

[jcanavera]

As noted earlier dependent upon the gauge of wire used to the plug and the cleanliness of the connections you might not have enough current flow. Take a look at your plug connections for evidence of dirt or corrosion. I used to have to squirt some electrical contact cleaner to keep good 12 volt connectivity on my SOB that used to have a 12 volt fridge. If that plug didn't have a clean connection, I could arrive at my destination with a dead trailer battery.

I remember also when my van was new, GM used to not place a fuse on that line used to supply power. It was done like that since they never knew if you were going to terminate the wire bundle into a connector.

Jack

[WindyJim]

I had the same problem when I purchased a 2004 25' AS and was pulling it with a 2005 Chevy Silverado.

I went back to the dealer and was very upset that I wasn't getting a charge to the trailer. He said often times the new pickups don't come with a fuse installed in the Chevy fuse block for the towing.

I doubted what he was saying, but he opened up the fuse block on my Chevy and showed me that there was no fuse installed. He popped one in and voila, towing charging working fine.

Check to see if you have a fuse installed in your tow vehicle, and if so check to see if it is good.

[Dwight]

TOWING; or connecting a trailer to the tow vehicle and idling the engine is very inefficient because the wires used are too small and too long. The voltage drop is excessive and you are lucky to get more than a few amps, once the tow vehicle’s battery is full and the voltage regulator tapers the charge rate to the vehicle’s battery. Turning the tow vehicle around and using big jumper cables connected directly from its battery to the trailer’s battery will give you much more power. That will get you maybe 10 amps (more if you have a big alternator) and up to 14.4 volts, which would take nine or ten hours to charge up that single battery. It will work, but it still takes a long time.

[AnnArborBob]

Even if your connections are perfect, you will get negligible battery charging while towing. Perhaps as little as 7 amp hours. Consider this a trickle charge that will help maintain a charge while using the trailer brakes.

[dznf0g]

I have checked amperage on several newer generation GM products. IIRC the charge line is a 12 ga wire. Per my trimetric monitor, at idle, the charge is 13 amps total (approx) and 10 amp net. By calculation, I have about 3 amps going to supply fridge and other parasitic loads. So 10 amps net, per monitor would completely charge my batteries, at 50% discharge, in about 12 hours. Of course, alternator output goes up with RPM. I usually am pretty full after an 8 hour drive.