Am I draining my battery when hooked to my trailer

tomseeley · July 25, 2006

I pull a travel trailer with my 2002 GMC 2500HD D/A. I occasionally "dry camp" without plugging the trailer into any electrical source. I did this recently, for four days straight, without disconnecting the cable from the truck to the trailer. Was I draining my truck battery in this configuration?

I used the truck (without starting it) to charge my cell phone battery for about 5-6 hours one day and the next day the truck started but the battery light stayed lit longer than it normally does.

It's hard to imagine that JUST charging the cell phone ran down the truck battery at all.

I need an answer specifically for my truck. On generic RV boards, I got a lot of "well, if you'd bought a Ford or a Dodge, they're wired so you wouldn't do that" kind of useless answers!

Thx

Frozen001 · July 25, 2006

I believe the +12 in the trailer plug is not covered by the Battery run down protection... Simple way to test is to put something that will draw a steady load on that pin and see if it shuts down.

Superman TNT · July 25, 2006

Not sure how experienced you are with camping.

First, I would assume that your camper has a 12v battery that it uses as a power source when you are not connected to 110ac. Is this true?

Most newer (1980 and later) campers have this. When you plug your camper into 110ac there is a charger in the camper that charges your campers battery. When you "run dry" which we call running self contined your are using power from this battery.

As for the truck connection . . . it depends on the age of the truck and if your RV plug was wired correctly or not. I will assume you have the standard 7 wire spaded RV connector. In that case the center pin (I think) is a +12v source for your camper (if it was ever wired correctly). A couple of simple ways to tell are

1) You can measure the +12 on the center pin with a volt meter

2) You can disconnect your campers battery and your truck connection. The lights in the camper should NOT work. Now plug your camper into your truck and check the camper lights again, they should work. If they do then your truck is wired correctly.

If your camper is wired correctly then every time you are driving (or your truck engine is running) you are charging your camper battery.

To answer your first question, "was I draining my truck battery in this configuration", the answer is yes, if your truck is wired correctly you were.

You are also correct about your cell phone. They use little or no power. Charging it shouldn't cause any problem at all. If it does I think you have other issues. I leave my radar dector on, cell phone pluged in and charging and my iPod plug in and charging over night and have no problem what so ever. In fact I don't even worry about it.

TNT

Shawn T · July 25, 2006

I pull a travel trailer with my 2002 GMC 2500HD D/A. I occasionally "dry camp" without plugging the trailer into any electrical source. I did this recently, for four days straight, without disconnecting the cable from the truck to the trailer. Was I draining my truck battery in this configuration?

I used the truck (without starting it) to charge my cell phone battery for about 5-6 hours one day and the next day the truck started but the battery light stayed lit longer than it normally does.

It's hard to imagine that JUST charging the cell phone ran down the truck battery at all.

I need an answer specifically for my truck. On generic RV boards, I got a lot of "well, if you'd bought a Ford or a Dodge, they're wired so you wouldn't do that" kind of useless answers!

Thx

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Yes you are using the truck battery. Without the alternator charging them, you essentially have your batteries wired in parallel. 1 or 2 on the camper and 1 or 2 on the truck depending on your configuration. Theoretically, (not technically, because of wire sizes and other variables that create resistance) you are draining your trailer and truck batteries at the same rate. If you have ample charge on your camper batteries, your truck should be OK. If you find that your camper batteries are becoming weak, I would start your truck and let it charge them up.

Frozen001 · July 25, 2006

But the question becomes is the trailer circuit protected by the battery run down protection... like the head lights/interior lights

Shawn T · July 25, 2006

But the question becomes is the trailer circuit protected by the battery run down protection... like the head lights/interior lights

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Nope, My enclosed trailer interior lights only work when plugged into the truck, because it does not have a usable battery (Just the small emergency, electric brake, breakaway battery). I have left them on for hours. When I went to start my truck, it turned over slow and luckily started. The Rundown Protection is essentially a 15 minute timer that shuts down the truck's accesories and lights. For some reason the +12V supply to the trailer plug is just a fused straight shot to the battery or batteries.

RazorKQ · July 26, 2006

But the question becomes is the trailer circuit protected by the battery run down protection... like the head lights/interior lights

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Nope, My enclosed trailer interior lights only work when plugged into the truck, because it does not have a usable battery (Just the small emergency, electric brake, breakaway battery). I have left them on for hours. When I went to start my truck, it turned over slow and luckily started. The Rundown Protection is essentially a 15 minute timer that shuts down the truck's accesories and lights. For some reason the +12V supply to the trailer plug is just a fused straight shot to the battery or batteries.

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I do the same as you sometimes with a tent trailer. I installed a second battery in the truck and ran a nice switch to it (mfg = Painless). It will be in circuit during running. Out of circuit when off. I also can switch it into circuit when off to give jump start if ever needed. It works great.