Permanent damage to tow vehicle battery?

[jymbee]

Just connect the “AUXILIARY +” wire to the positive terminal on the towed vehicle battery! That will fix this. Easy.

Were it only that simple...
This is an issue we've been dealing with and have 3 different repair folks try to resolve. Unfortunately, some were obviously over their heads. It's a 6 pin cable and the power is not getting to the connection on the coach. One outfit in Austin found and fixed a wiring problem along the way and I thought it was resolved only to have it reappear.

 

[John From Detroit]

While I understand the regs in some states that require an aux brake, it's never been clear to me just how effective they actually are. I brake the coach, see the light on the remote controller come but I can't see it "feels" any different than the times I've driven when the brake wasn't working.

How effective they are I can not tell you in numbers but this I can tell you
E=MC^2 This means the amount of energy you must dissapate when you stop (The braking power needed) is equal to the MASS of the consist (Motor home plus towed) Times the square of it's speed. Double the speed. quadruple the energy needed to stop (And the skid distance)

The other side of the equation with all wheels locked is the coefficient of friction between tires and road and the WEIGHT of the vehicles. and of course time or if you like distance skiddeed.

IN theory a Yugo and a fully loaded semi.. Turns out they use the same formula to estimate speed based on skid distance. Yup.

But now let's have wheels turning free (No brakes on towed)

Now we have more mass to stop. and less weight to press wheels to road. So it gets far far more complex and you skid farther. Some days 1 foot is enough to make a difference.

 

[Kirk]

I'm well aware that although I might not experience any difference any difference, the aux brake might well be most effective were I ever need to brake hard unexpectedly.

While E=MC² has nothing to do with your situation, (C² is the speed of light squared), Kinetic energy is directly proportional to the mass of the object to the square of its velocity (K.E. = 1/2 m v²). Just how effective your auxiliary brake is, depends on how you have it set up and several other factors. The simple answer is that it probably is only really needed in an emergency or sudden hard stop.

To say my driving technique when towing is conservative would be an understatement. Always looking far ahead for issues, start slowing down gently well before any stops and in general chugging along at no more than 60 MPH even on highways with a 75 MPH limit.

I think you should do fine since you are aware of the lack and adjusting for it. Many folks tow a vehicle behind their motorhomes for years without any auxiliary brake and never have a problem. While I would not make a practice of it, I'm also one who goes to the conservative side of most safety issues. Just be extra careful.