Lowdown on trailer charge wire/general electrical?

joecool911 · #1 01-23-2013, 11:42 AM

I'm wondering how the trailer charge wire is setup? Stock tow package. Does it have an isolator? Does it charge the truck batteries when the trailer is plugged into 110 and my trailer charging system is charging the trailer battery? Could the trailer possibly drain the truck battery when drawing 12 volt in a deficiency situation?

I also have a dumping trailer and the truck does keep the battery on that charged.

Is there any isolation or separate draw from the two batteries under the hood? Or is it just one big 12 volt system?

Also wondering about bigger amp batteries. My dash gauge goes down a lot when I first start up in the am. Probably to about 10 volts. Wipers slow and lights dim when the heat plate cycles on and off.

RAW · #2 01-23-2013, 12:22 PM

There is a relay, controlled by your headlight switch, that supplies power back to your trailer. Only when your headlights are on will power be shared.

The issue with the lights dimming is how much power the grids can take. Up to 200 amps can be pulled by them, with an alternator that only makes 135 amps. Your batteries could be weak if it pulls down to 10 volts. Mine cycle down to about 11.4 or 11.7 volts, depending on how long they sit, and the batteries are in decent shape.

joecool911 · #3 01-23-2013, 01:10 PM

Got out my VOM. Battery started out cold @ 12.4. Turned on ignition to warm plate for startup. Went down to 11.2. Started truck and went to 14.6. When heater plate cycles, goes down to 12.5 and back up to the 14.6. Sounds pretty reasonable to me. See what you guys think. Temperatures overnight 25*. Not plugged in to block warmer.

This is an awesome forum. You guys are greatly shortening my cummins learning curve. Thanks! Someday I'll be able to contribute more in return.

RAW · #4 01-23-2013, 01:16 PM

That sounds reasonable to me. How cold is it?

joecool911 · #5 01-23-2013, 01:51 PM

Originally Posted by RAW

That sounds reasonable to me. How cold is it?

Been teens last week or so, but 25* last night.

RAW · #6 01-23-2013, 01:57 PM

So 10 to 15 seconds of up to 200 amps of power draw, that is a good bit of power flowing. Followed by a 500 amp peak draw by the starter. I'd say your batteries are in decent shape. If it becomes a problem, you can upgrade the stock size, or increase the Battery size. With modification to the battery boxes, group 31's can fit in there.

Bryce · #7 01-23-2013, 09:00 PM

If the trailer is only plugged into a 4 way flat plug then no power is transfered until the lights are actuated. But if you have a 5 or 7 way round plug then yes power will be transfered to the battery on the dump trailer when it is plugged in. I don't know if having the trailer charger plugged in will charge the truck or not but I would assume it would.

---AutoMerged DoublePost---

Oops mistype. That was supposed to say 6 and 7 way round. 5 way does not have a hot wire to the plug.

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