Do I need a diode on towed wiring?

[dpinvidic]

Originally Posted by walt2137

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.

Walt,
I am not saying that you will have a problem.
What happens is that the TOAD will see about 13V from the coach.
This is not really enough to charge a battery...but that does not matter.
What matters is the any current that the TOAD requires will be coming from the Coach (since it is a higher voltage). So having the diode really just prevents discharging the TOAD battery...and to some extent can give it a partial charge when the coach is putting out 14.5 volts (bulk charge voltage).

Randy, The reason they tell you to disconnect the neg terminal is to prevent draining the battery because you need the key in the "ON" position.
Running a charge line is fine instead of disconnecting the neg. terminal.
HOWEVER, for time that you may stop overnight and leave the toad connected, you need to be sure to turn off the key...otherwise you will put a current drain on both the coach & toad batteries.

The main purpose of the diode is to prevent draining the coach batteries if something goes wrong....like the AUX brake system keeps the brake pedal depressed (toad brake lights on). This will drain the coach & toad batteries if there is no diode.

Regards,
Dan

[BFlinn181]

Originally Posted by walt2137

The diode is cheap easy to rig up and does the job.

But the question is, What job? The job of reducing the voltage forward to the Toad battery? It serves no other purpose if you have good habits when you stop for the night. I always walk back to the toad, unplug the auxiliary brake and the signaling device that lights up on my dashboard when the brake is applied or blinks when not working properly. I lock the ignition and remove the key, locking the car for the night. I walk around the whole rig, checking tires and touching wheels looking for heat in uneven amounts.

At that point, both battery systems have been charging all during travel and neither is drawing from the other since they're in stasis. What job is the diode doing at that point?

[dpinvidic]

Originally Posted by BFlinn181

But the question is, What job? The job of reducing the voltage forward to the Toad battery? It serves no other purpose if you have good habits when you stop for the night.

YES..absolutely true. But we sometimes forget , just because we are human. OR something goes wrong on the toad....like maybe the AUX brake system ends up depressing the brake pedal inn the middle of the night.

The diode is strictly a preventative device. Like the safety valve on the water heater...have never needed it yet...but would never take it out.

Regards,

Dan

[walt2137]

Quote:
Originally Posted by BFlinn181 View Post
But the question is, What job? The job of reducing the voltage forward to the Toad battery?

Well Bob it has worked for 13 years for me, I understand you do it a different way and thats ok with me but your way is not the ONLY way to accomplish this and I will say again the charge wire only job is to keep the battery up and my installation does that for me with a toad brake( Roadmaster Brakemaster ) that lights up my brake lights on my toad every time I hit the coach brakes, the diode will stay in my toads.

[twinboat]

The only thing a diode will do is prevent the toad from charging the MH.

As a one way valve, with both vechicles shut off, the current will flow, from the MH, to the toad battery.

If the toad is draining it's battery, the diode will let the MH current, flow in that direction. Over time, all of the batteries will go down.

If the charge wire was hooked to one side of a double diode isolator, the alternator to the center and the MH battery to the other side, then it would stop current flow, between the two vehicles.

Think about It.

[nothermark]

Diodes and fuses are both good safety devices. Some folks are just too stubborn to deal with it. If you want to reduce the voltage drop look around for power shottky diodes as the drop is about half that of a regular junction diode.

FWIW on the Ford class C chassis the 12 V line for the 7 pin connector is fused and switched by the ignition. If one taps that there is no need for anything else. That said I would stick in a diode just to make sure a problem with the coach did not bleed down my backup vehicle battery. If I was wiring an F-53 chassis I would check that as it probably does the same thing thus saving the cost of a protector relay.

[Qwert66]

More food for thought.

For my particular case I wish I would have wired my coach thru a diode to the toad battery and use the toad plug lighter to run my brake.

As stated earlier I choose to run the coach to a separate cig lighter plug in the toad which runs the aux brake. Also I unplug the umbilical cord and power down the brake when not needed and at night.

Everything works to my liking except 1 thing!
I have to start the RV prior to powering up the brake in the toad or else the brake will fault out due to momentarily seeing a drop in voltage (during cranking) requiring it to have to be reset and re powered up. I would prefer to power up the brake and then go inside and start the Diesel. I use the Blue Ox Patriot brake and this happens even with new fully charged coach batteries most of the time.

[Timon]

Originally Posted by 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.

if the toad battery was fully charged but the coach battery was not the toad battery could be over charged. Not likely but posiable.

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.

You don't as it's not something you actively monitor. The Toad Charge MUST be in the toad it's never in the coach so you can never see it while traveling.

The other thing it does is act as the circuit breaker on the toad side. If you connect directly, with or without a relay in the coach, you still need a circuit breaker on both the coach and the toad for safety. I figure if you're going to get a circuit breaker for the toad why not put in a Toad Charge as the cost compared to everything else you need to tow is pocket change.

[mgscott4]

I installed this kit. No problems for 5 years now. No backfeed, no battery drain.

Tail Light Isolating Diode System with Wiring Harness Hopkins Tow Bar Wiring 38955


If you need anything towing related, these guys (Etrailer) are great to deal with. Highly recommend them.

[twinboat]

mgscott4,

That is a tail light kit. It does not charge or maintane a battery.

It does stop back feed to the toad wire harness.

Back to the diode thing,

Make, battery A (MH) and battery B (Toad).

Sit A next to B. Put a diode between A & B pointing to B.

Now start draining B.

As B goes down, A follows, thru the diode.

If you drain A, B will stay charged .

If MH is dead, you can start toad.
If Toad is dead, MH could be dead.

Relay much better idea.

[YC1]

If you want simple isolation with no voltage drop just use a good relay. Simple and effective.

[Hit_the_Rhod]

Here's a question for you guys. I just finished up wiring my toad (2004 Honda Element) with a 6 pin trailer plug according to the wiring charts on the internet for 6 pin plugs. Motor home was already wired. I did not use the trailer brake wire on the toad part of the wiring because I am using a Brake Buddy with uses inertia to activate the brakes. Here's the problem. All the lights work properly except . . . . the brake light filament is on VERY dim all the time. And it is back feeding somehow into the rear tail lights of the motor home, causing THEM to be on very dim any time the umbilical is plugged in. I am not wired into the wiring on the toad at all except for a hot lead (center pole) to the toad battery which goes through a resettable inline circuit breaker . . . . any thoughts?

[SilverBob]

Originally Posted by YC1

If you want simple isolation with no voltage drop just use a good relay. Simple and effective.

Yeah, I suggested that in the third post in this thread! Apparently some folks are caught up in diodes, so ... whatever!

[twinboat]

Open the plug and the socket and check for a few strands of wire crossing pins.