Bronco Running down while towed

[stokesrl]

I’m towing my 2023 2 door behind a motorhome. I have a wire running from the charge wire from the motorhome
To the positive terminal of the battery (with a diode between). I measure 14.6 volts from that charge wire into my battery. My issue is that the battery runs down while I’m towing it. I left with the battery at 12.6 volts and within an hours, it was 12.1 volts.

I never hit the brakes, so the stay in play isn’t running it down. Surely the computer while in tow mode can’t be drawing more that the camper can deliver?

Any ideas?

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[grtharris]

Right off it sounds like you either have a bad connection on the positive or negative side of the battery. 14.6 volts is high at the battery if Bronco battery is pulling any current from the coach there should be some voltage drop in the wiring.
Now why is the Bronco going down. First guess is a bad battery should not drop that fast.

 

[Travler]

Like the other Gentleman says , I would all the connection even the Ground on Motor home

 

[Coosguy]

Get the rvi towed battery charger

 

[Bill K]

I’m towing my 2023 2 door behind a motorhome. I have a wire running from the charge wire from the motorhome
To the positive terminal of the battery (with a diode between). I measure 14.6 volts from that charge wire into my battery. My issue is that the battery runs down while I’m towing it. I left with the battery at 12.6 volts and within an hours, it was 12.1 volts.

I never hit the brakes, so the stay in play isn’t running it down. Surely the computer while in tow mode can’t be drawing more that the camper can deliver?

Any ideas?

I second the inspect all connections advice. I have seen the connection cable ends I use from Blue Ox be a little intermittent sometimes. Note that on the Bronco connector, the wires are secured by screws into the stripped wire. An ohm meter might come in handy as you likely have a high resistance either in the charge or ground return line... A good piece of long wire to run in parallel to use your meter will help diagnose with everything connected and the connection at the battery disconnected and the fuse pulled in the motorhome for the positive side anyway.

 

[BadlandsA51]

You mentioned being connected to the B+ terminal, but didn’t mention how you connected the negative terminal. It must have a good connection to the same ground as the towing vehicle’s battery. No ground, no current flow, no charge.

 

[stokesrl]

It has 4000 miles and is just a few months old- but I guess a bad battery is possible- although it starts flawlessl

You mentioned being connected to the B+ terminal, but didn’t mention how you connected the negative terminal. It must have a good connection to the same ground as the towing vehicle’s battery. No ground, no current flow, no charge.

i need to check- I’m sure it’s connected to the ground coming through the coach connection- but maybe I need to run a ground from there directly to the battery

 

[BadlandsA51]

It has 4000 miles and is just a few months old- but I guess a bad battery is possible- although it starts flawlessl

i need to check- I’m sure it’s connected to the ground coming through the coach connection- but maybe I need to run a ground from there directly to the battery

Or you could just hook everything up and measure voltage between the Bronc’s battery negative terminal and tow vehicle’s negative battery terminal.
Turn the Bronco’s key on, and the lights and heater blower without starting the engine, this will load the charge circuits. You should measure 1V max between the two batteries negative posts. You could run the same check on the positive posts of the 2 batteries. It should be less than a volt also. The lower these voltages, the better.

 

[stokesrl]

I assume it’s ok ( or necessary) for them to share a ground

 

[BadlandsA51]

Yes, the tow vehicle will be the charging system for the Bronco. The Bronco’s battery has to be grounded to the tow vehicle, just like the tow vehicle’s battery is grounded, otherwise no current will flow through it.

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