Will the P2 Brake Controller Make Batteries Go Dead on a 2008 Dodge Ram Diesel

Question:

In January this year the batteries in my 2008 Dodge Ran Diesel were dead. Dealer said one battery had to be replaced. On March 6, 2010 the batteries were dead again. Purchased the truck in April 2008. It has 7100 km. and installed the brake controller by plugging it into the factory harness and it worked fine. Owned the brake controller since 1999 Had it in my 96 Dodge Ram Diesel. No problem. I do not use the truck too often in the winter time and had no problem in the past due to dead batteries. Last winter was a lot colder than this one, No problem. Truck is parked out side. The dealer is stating the brake controller is drawing on the batteries and that is why they die when the truck is parked too long. They suggest I pull the fuse to the brake controller when it is parked too long. I think they are in left field. Question: Is it possible what they say is true? How many amps or millivolts does it draw when parked? Thank you for your attention.

asked by: Paul A

Expert Reply:

I know how much a dead battery can be a real annoyance. Based on the history you have outlined with brake controller, it seems as though there might be another, unknown cause making your batteries go dead.

Basically, the brake controller, when on, only draws a few milliamps and would take over 10,000 hours to drain. That is equal to over a year. About 417 days, or 1 year and 2 months at least! The P2 does not draw power when it is off and it shuts off automatically after 15 minutes. So it seems unlikely that the brake controller is making the batteries go dead.

I suppose if you wanted to, you could pull the fuse or disconnect the power to the brake controller from the battery and wait and see what happens. Otherwise I might look at getting the batteries and alternator tested after you eliminate the brake controller as a possibility.

expert reply by: Michael H