Keeping Tow Car Battery Charged while Towing!

I went with the RVI system:
http://www.rvibrake.com/RVibrake-Towed-Battery-Charger-p/tbc-12014.htm

Brake Buddy has a less expensive one.

On the Honda Fit with GPS (maybe all other Hondas with GPS?), when you turn the key to unlock the steering column, the GPS runs, cooling fan and all. The Fit in particular has a silly looking miniature battery. As much as I like Hondas I think their GPS power operation is all screwed up. EVERY time you start the car, you have to press the GPS's CYA button to use it. But the unit un-powers when cranking the engine, so if you program it before starting the engine, you have to do the CYA button and setting the GPS mode over again. Seems about as backwards as backwards can be.

I have been watching this thread for ideas as I have a similar problem.

I have a 2002 Dakota, four wheel drive with automatic transmission. When the key is in the unlocked position, as far as I can tell, there is no power to anything except the shift display.

I have a mechanical surge brake that is connected to the Dakota brake pedal which activates the Dakota brake lights when stopping.

After a long day of towing the battery in the Dakota discharges. Three times it has discharged the battery completely.

I ran a powered wire to the rear of the RV and connected it to the positive post of the Dakota battery.

I was thinking this would be the simplest way to keep the Dakota battery topped off.

This thread interested me because I was wondering about the drawbacks of doing this or if there was a better way to do it.

Some have mentioned using a diode in this type of setup in order to prevent the discharge from the toad from affecting the RV battery.

So I was just wondering if there is any issue with just simply running a powered line to the toad without any extra stuff such as diodes and the like.

I am also wondering if there is a better way to do this that is simple and easy.

We do like bumpy said. Works great.

Thanks for the answers.

Maybe I'm just being overly cautious, but reading about Towing the newer Cars with all their Electronics and such has Me a bit more concerned.

Our Old Toad ...A 92 Tracker was easy if and when the battery failed I could just jump start it!

It is nearly impossible for Me to reach the Fuses in this New to Us Honda CRV to either pull Fuse #XX or install a Switch to do that.

I figured I would just tie in to the available power supply on the Motorhome and keep the Toad supplied with juice.

I have to also consider what else may be connected to the Keyed 12 Volt power source. Just in case something gets fed power back from the Toad end .

That is why I thought a Diode might be the answer however if it lowers the charge then maybe is not such a great idea.

A simple Switch or relay would also work ,however that might get forgotten at some point which would defeat the purpose entirely.

Of course just unplugging the Cable is also an option,but then again ??

I may just have to rethink the power supply point and install a dedicated circuit that has nothing at either end which can get fried!

A fused wire connected to the toad positive terminal takes care of keeping mine topped off when underway. A charging wire is needed by most new model toads because of all the computer related stuff that can't be shut off.

what is on in the toad that draws so much juice it runs down the battery? I used a brake buddy and plugged it into a small jumper/starter battery thingy that I wanted along anyway.
bumpy

I hook ignition-switched power from the motorhome directly to the dinghy battery, fused on both ends. No diodes, and no problems after a few years of use.

The diode might come in handy as it would assure that once the vehicle is stopped and off, the towed's battery will not be drawn down to share with a weak chassis battery. A diode will also lower the voltage received by the towed.
Your vehicle's charging system is a regulated system. When the towed battery and chassis battery are fully charged, the vehicle's alternator will not push any more current then is necessary. Unless you have a failing chassis battery, it is nearly impossible to damage the towed's battery.