Do I need a diode on towed wiring?

[dpinvidic]

Here are the details on using a blocking diode.
A diode acts like a one way valve, current can only flow in one direction.
So, yes, it can prevent the toad from discharging the chassis battery.
The problem, is that a diode has a voltage drop. So when the coach is putting out 13.8v for a float charge, the toad will see about .6v less. This is not a problem, but your not giving the toad a full float charge level.

Now a relay can prevent the discharge because it will open when the coach is not running.
But the toad will receive the full charge voltage. This is exactly what the boost relay does between house and chassis batteries.

Freightliner already puts a relay on the 12v charge line of the trailer connector.
A directly connected charge line will not hurt anything

Regards,

Dan

[Timon]

I think the simplest way is to just use a "Toad Charge" as stated earlier. Not only does it isolate it has indicators to let you know it's working.

[BFlinn181]

Originally Posted by Timon

I think the simplest way is to just use a "Toad Charge" as stated earlier. Not only does it isolate it has indicators to let you know it's working.

They cost about $50 and are usually installed in a compartment. A little hard to see the pretty LEDs when it's buried. I wouldn't call it a simple way. An auto reset circuit breaker is the simplest way. Unless the car battery is bad or left with some accessory drawing a lot of power, the two battery systems will neither rob or overcharge the other system - - it's a fact of physics.

[YC1]

You do not need a diode. A lot of vehicles simply supply power through a relay so there is no voltage drop associated with that.

Even without a relay or diode you are fine. If it makes you happy then simply unplug at night and reconnect in the morning. Why install a device that drops the voltage, produces heat, and adds two more connections that can fail.

I too prefer resetting breakers at each end versus fuses. They are inexpensive and will reset themselves in a few seconds.

Senior Certified Electronic Tech

[Timon]

Originally Posted by BFlinn181

They cost about $50 and are usually installed in a compartment. A little hard to see the pretty LEDs when it's buried. I wouldn't call it a simple way. An auto reset circuit breaker is the simplest way. Unless the car battery is bad or left with some accessory drawing a lot of power, the two battery systems will neither rob or overcharge the other system - - it's a fact of physics.

Both use an auto resetting circuit breaker but the Toad Charge does protect the toad battery from being over charged as well.

Being able to see the lights depends where you mount the Toad Charge in the Toad. If mounted behind the grill it could be viewed without opening the Toads hood.

[BFlinn181]

Why would the 12 v battery in the car be overcharged by a 12 v alternator in the RV? Wouldn't the chassis batteries be at risk for damage by overcharge long before the Toad battery? I'm sorry, it makes no electrical sense. As to mounting the toad charge in the grill of the toad, how are you going to monitor it driving the RV down the road? Your rear camera? Who's going to be watching the road if you're staring at the monitor, looking for a red, green or yellow LED? When we park, I always go to the toad and unplug the braking system, remove the ignition key, and lock the doors. No issues of my battery discharging overnight.

[ronspradley]

Thanks again all. I will try and get the towed wired today (depends on weather, scattered showers this morning, scattered thunder boomers this afternoon). I already have 20 amp in-line fuses in my electrical box, so that is what I will start with. Not going to start with circuit breakers or diodes. Will evaluate and go from there. MH is parked at my sister's place 80 miles from where I live in sticksnbricks. Should be going there next week and will test.

ronspradley

[Qwert66]

Food for thought.
I simply ran a 12v fused line from the chassis battery (thru the umbilical) to a SEPARATE fused lighter plug in the toad for the brake. My trailblazer does not require the key to be left on so that's why it works.

We would never leave our 6 wire $80 umbilical cord plugged in when we are not there or at night in a parking lot as it may "walk away" and we don't carry a spare. Same for the safety cables. Our tow bar pins are the locking kind so they stay on. We see many toads bt themselves with the blue ox inserts waiting to "walk away" as well. Yes we are honest but why take the risk.

[rmcobb]

OK, I'm trying to follow all this as I'm setting my Toad up as well. I have to leave my key on (2008 Dodge Dakota) and they say to disconnect the neg battery terminal. I'm thinking thats a pain, and would just like to put in a charging wire to the Toad.

So, if the 7 pin or 6 pin at the Coach already has a pin dedicated to 12V charging, why couldn't I just wire up the 6 pin that will stick out the front of my toad with a charging wire to the toad battery, and use that main connector cable to accomplish the task.

That way, I don't have another wire to connect/disconnect. It would all be handled by the same wiring connection that is taking care of the brake lights, turn signals, etc.

Is that possible?

Randy

[BFlinn181]

Originally Posted by rmcobb

OK, I'm trying to follow all this as I'm setting my Toad up as well. I have to leave my key on (2008 Dodge Dakota) and they say to disconnect the neg battery terminal. I'm thinking thats a pain, and would just like to put in a charging wire to the Toad.

So, if the 7 pin or 6 pin at the Coach already has a pin dedicated to 12V charging, why couldn't I just wire up the 6 pin that will stick out the front of my toad with a charging wire to the toad battery, and use that main connector cable to accomplish the task.

That way, I don't have another wire to connect/disconnect. It would all be handled by the same wiring connection that is taking care of the brake lights, turn signals, etc.

Is that possible?

Randy

Yes, but for safety to include an auto resetting circuit breaker between the toad bumper socket and the battery terminal. Make sure your socket and umbilical also has a ground wire that connects to the ground in the toad. It's an iffy connection if the toad socket isn't connected to ground.

[Qwert66]

Another typically missed item when using the umbilical cord for passing the 12v dc power is as follows;

Guy wants a lot of current to charge the toad.
Wires a 10 or 12 gage wire properly fused at 20-25amp or so from the RV battery to the trailer plug.
Does the same in the toad for the 6wire front plug fused to the battery.
Plugs in the (undersized) umbilical cord with a 16 or 18ga wire for the 12+ line and melts the umbilical cord.

All great advice here, and make sure you don't over fuse the charge line for its smallest wire in the system loop.
Most 6 wire umbilicals will have a larger ground wire to pass everything back but the 12+ feed wire may only be rated at 10-15amps.

[BFlinn181]

Originally Posted by Qwert66

Another typically missed item when using the umbilical cord for passing the 12v dc power is as follows;

Guy wants a lot of current to charge the toad.
Wires a 10 or 12 gage wire properly fused at 20-25amp or so from the RV battery to the trailer plug.
Does the same in the toad for the 6wire front plug fused to the battery.
Plugs in the (undersized) umbilical cord with a 16 or 18ga wire for the 12+ line and melts the umbilical cord.

All great advice here, and make sure you don't over fuse the charge line for its smallest wire in the system loop.
Most 6 wire umbilicals will have a larger ground wire to pass everything back but the 12+ feed wire may only be rated at 10-15amps.

15 amps at 12 volts is 180 watts. As long as the RV and the Toad have healthy, charged batteries, you shouldn't cause such an imbalance of the two systems to cause excessive amperage. If you're worried about exceeding your wiring capacity, you could reduce the auto reset circuit breaker to 10-15 amps.

[walt2137]

Originally Posted by dpinvidic

Here are the details on using a blocking diode.
A diode acts like a one way valve, current can only flow in one direction.
So, yes, it can prevent the toad from discharging the chassis battery.
The problem, is that a diode has a voltage drop. So when the coach is putting out 13.8v for a float charge, the toad will see about .6v less. This is not a problem, but your not giving the toad a full float charge level.

Now a relay can prevent the discharge because it will open when the coach is not running.
But the toad will receive the full charge voltage. This is exactly what the boost relay does between house and chassis batteries.

Freightliner already puts a relay on the 12v charge line of the trailer connector.
A directly connected charge line will not hurt anything

Regards,

Dan

Dan you are correct the diode does cut down the voltage going to the toad but I have used a #12 wire (and I know #10 is generally used) and diode on the charge line on the following toads and have never had a problem with a dead battery even after towing a few times close to 700 miles at a time. 03 Honda Element, 10 Chevy Equinox, 11 Edge, 13 F150, 14 Chevy Spark and a 15 Kia Soul. The diode is cheap easy to rig up and does the job.

[walt2137]

Originally Posted by Qwert66

Another typically missed item when using the umbilical cord for passing the 12v dc power is as follows;

Guy wants a lot of current to charge the toad.
Wires a 10 or 12 gage wire properly fused at 20-25amp or so from the RV battery to the trailer plug.
Does the same in the toad for the 6wire front plug fused to the battery.
Plugs in the (undersized) umbilical cord with a 16 or 18ga wire for the 12+ line and melts the umbilical cord.

All great advice here, and make sure you don't over fuse the charge line for its smallest wire in the system loop.
Most 6 wire umbilicals will have a larger ground wire to pass everything back but the 12+ feed wire may only be rated at 10-15amps.

You are correct and only one company made the umbilical with #12 wire when I researched and that is the umbilical I use, I don trembler which it was but think it was Roadmaster.