Battery Keeps Dying on Tow Car

Sounds like there's something that stays on in the Honda when towing, that is running the battery down. Very common, actually, and is the reason folks pull fuses, disconnect the battery, or run charge lines.

Constantly running a starting battery down like that will shorten its lifespan significantly, and really needs to be avoided one way or another. Starting batteries like are found in vehicles are not designed to be drawn down that low.

Put an ammeter across one of the main wires going to the battery, when the vehicle is basically in same mode as when you're towing it - key in ACC position if it has to be, everything turned off, tranny in neutral, all doors closed so no interior lights are on, etc. See what kind of amps are being drawn from the battery.

You're probably going to find there is something drawing it down. I found with our Ford Fusion hybrid, that even when I had everything turned off, there was still a 3 amp draw on the battery. This was making the battery weak even after just a 4 hour trip, so I had to do something.

Your choices to fix this are:

1. Find whats drawing it down and stop it, usually involves pulling a fuse (just one more thing to have to do when hitching and unhitching)
2. Disconnect the battery when towing (again, one more thing to do, and have to reset several things, ugh!)
3. Run a charge line from MH to towed vehicle, through the umbilical cord if possible (best choice if you can do it)

I opted for choice #3, and its worked great. MH already had a fused charge wire on the back, from the 7-way connector. Just wired that into one of the extra lines of the 6 way umbilical cord, wired it on the car side over to the battery with #10 gauge wire, and a 10 amp fuse. Also upgraded the ground wire coming from that umbilical cord connection to #10 gauge wire (on the towed vehicle).

Works great, you never have to worry about running down the towed vehicle's battery again. Towed vehicle's battery is fresh and fully charged when you get to your destination, no matter how long you've been towing. Even if you use one of the brake systems that can draw down the towed vehicle's battery, that is no longer a concern, either.

Our Dakota does the same thing. I always carry a jumper pac from Black & Decker. If I disconect the battery, the Idiot light in the MH,won't work, for the brakes. We have two brake light bulbs in each tail light, and I like both to come on. The magnetic lights don't show up very well, from behind.

On our 12 CRV, just turning off the heating controls and radio button does not necessarily turn everything off. Things are still running in the background. See pages 236 of the 12/13 owners manual and it will say to pull an accessory fuse.
We had problems even with the charge line from the MH blew a fuse, CRV battery was almost dead a drawing too much power, blew fuse.
I was surprised when I got in the car to disconnect and looked a display reading ' Audio System is Off, Now connecting Bluetooth to Cell Phone' which was in my pocket

Beverley and Ken

I just have quit disconnect on my battery of the towed. I use magnetic lights for the towed.

rv4jimnme wrote:
First time we have experienced the tow car not starting. We frayed the electric connection cord (the one that runs from coach the towed car), since we did not know it was dragging on the ground. So thinking this was the problem we bought a new one and the problem went away for about 3 weeks of travel. Yesterday, however we arrived at our campsite and the Honda CRV would not start, so had to call Good Sam for a jump start. We had the battery in the Honda tested and all connections everything checked out fine, that was about 3 weeks ago on the first episode. Everything is turned off in the Honda i.e. no fans etc. We also do not tow with the alarm on. Upon starting the car this AM I noticed that the Alarm bleep, the sound it makes when you unlock the car, is noticeably "weak sounding" not as loud as it always is. Just an off the wall observation.
As a side note: At first we felt maybe, this was in some way connected to the fact that we convert our power on the road to run a computer, we always use the house battery plug in for this. However, the GPS I have been plugging into the engine battery (cig lighter) thing. Could this have anything to do with draining the tow car battery? Thanks for any help or advice.

Jim did you remove the ignition fuse from the Honda when towing? just asking.:W

Have you checked the owner's manual for your Honda? Some vehicles require certain things to be done, such as starting the car every day, or removing a certain fuse, etc, while being towed.