Charge circuit diode?

WyoTraveler: I just now read your previous post, where you explained more specifics of how NOT having a diode is affecting your MH's operation. Did not realize, or think about the fact that the toad back-feeding current could cause various parts of MH to not work (slide, shades, etc), since the current back-feeding apparently makes it 'think' the ignition switch is on.

Very interesting point, and has me wondering if mine would do the same thing. We've only taken two trips so far since I put in the charge wire, and that has not been an issue. However, in our case the toad has long since been unhitched and disconnected before we deploy or bring in slideouts or anything like that. Sooo, we probably would not have noticed this.

Think I may have to do an 'experiment' in the driveway, and see if slideouts, etc. will work when toad charge wire is hooked up. If not, then a diode upgrade may well be in my future.

Will

The problem is many things are tied in on the opposite side of the ignition switch in different places. Key has to be off to run slides, & front shades. Key on to run jacks. I could break into the ignition line and mount a relay in front of MH. & run a #10 wire all the way back 34 ft. Or I could mount relay in back & run lighter control wire all the way back. On a PU charging a TT battery you would never ntice the problem. I could unhook the plug every time I stop. Or use a diode in the charge line. I temporarialy used a diode today and all worked ok. Hard to find heavy duty diodes while on the road. Radio Shack in Idaho had some 6 amp diodes for 75 cents each. Used 2. Al worked ok. When I get back home will make it more permanent. Still cheaper than buying a TOAD charge which basically does the same thing.

..Interesting topic here.

I just wired a charge line to our Ford Fusion, doing it the simple way - used charge wire already on back of MH, wired it to toad battery by using one of the wires in the 6-round umbilical cord. Wire was/is already fused on MH side, and I added a 10 amp fuse on Fusion/toad side, right before the battery. Used 10 gauge wire for the charge line as well as ground wire in the toad.

Has worked great, keeps battery in toad charged up fine. Have not installed a diode on the charge line, but now after reading some of this discussion, wondering if maybe I should?

Worst that could happen if you didn't, I'm thinking, is that if you left it all plugged up overnight or longer, you could possibly run down your MH's chassis battery(s), causing MH not to start.

I haven't really worried about that, though, as we almost never do that (leave it plugged up overnight), and if we did and ran down the MH's battery, our MH (and I'm sure many others), has a 'boost' button on the dash you can push that will connect the house batteries to the chassis batteries, to give chassis batteries an extra 'boost' when needed. Long as your house batteries were in good shape (or you were running your genny), you could use the boost button to get things started (right?)

Not crazy about the voltage loss some mentioned, that would go with using a diode. What to do, what to do...

aslakson wrote:

Better yet just unplug at the trailer connector.

Unfortunately, once our toad is all hooked up with tow shields, etc, in place, it's quite a chore to get at the cable to plug or unplug. Unplugging at the car end requires removal of the tow shield, and at the MH end removal of the bikes on the bike rack. Also some acrobatic skills are required that are beyond my old bones. We try to have the toad all hooked up the night before we leave, just to make departure easier. So, it's connected overnight before we roll.

As far as the relay, I'll have that explored next time we get near our regular RV service facility. Hooking up a diode I can probably handle myself. Not sure about a relay.

Thanks

al

If you can hook up a diode then you can add a switch. Tradeoff is that it's now a manual operation but no voltage drop for charging due to the diode.

OldF**t wrote:

WyoTraveler wrote:
The problem with a relay is I would have to add a switch on the dash & 35 ft of wire back to the rear of MH & relay. The toad feeds voltage back on the back side of the ignition switch. It looks like key is on so slide won't work. (you have to have key off). Camera stays on. A toad charge does what a diode does for $80. Bottom line a relay wouldn't shut when you turn off ignition because of toad battery feding back. An ideal diode would be germanium. Doubt you can buy them any more. Schottky diodes do have lower voltage drop. Just hard to find electronic parts anymore.

Maybe I'm just confused but it seems like you're making this more difficult than it has to be. I would find where the toad charge line is fed at the front of the motorhome. Splice in the normally open contacts of a relay to that charge line. Wire the relay control lead to a +12v feed controlled by the ignition switch. You turn off the ignition switch, the relay drops out, and the charge line to the toad is opened. You already have a charge line wired back to the rear of the mh. Why would you need to run another one? Sorry if I am misunderstanding your situation but that's the way I would do it if I needed a way to automatically disconnect the charge line. In my situation I just unplug the cable.

X2

WyoTraveler wrote:
The problem with a relay is I would have to add a switch on the dash & 35 ft of wire back to the rear of MH & relay. The toad feeds voltage back on the back side of the ignition switch. It looks like key is on so slide won't work. (you have to have key off). Camera stays on. A toad charge does what a diode does for $80. Bottom line a relay wouldn't shut when you turn off ignition because of toad battery feding back. An ideal diode would be germanium. Doubt you can buy them any more. Schottky diodes do have lower voltage drop. Just hard to find electronic parts anymore.

Maybe I'm just confused but it seems like you're making this more difficult than it has to be. I would find where the toad charge line is fed at the front of the motorhome. Splice in the normally open contacts of a relay to that charge line. Wire the relay control lead to a +12v feed controlled by the ignition switch. You turn off the ignition switch, the relay drops out, and the charge line to the toad is opened. You already have a charge line wired back to the rear of the mh. Why would you need to run another one? Sorry if I am misunderstanding your situation but that's the way I would do it if I needed a way to automatically disconnect the charge line. In my situation I just unplug the cable.

Another option is to take a fuse, cut off the top, wire in an ON/OFF switch and a fuse holder for another fuse. Then, you don't have to pull a fuse, you just flip a switch. I have seen one for sale on the net, but don't remember where.

The problem with a relay is I would have to add a switch on the dash & 35 ft of wire back to the rear of MH & relay. The toad feeds voltage back on the back side of the ignition switch. It looks like key is on so slide won't work. (you have to have key off). Camera stays on. A toad charge does what a diode does for $80. Bottom line a relay wouldn't shut when you turn off ignition because of toad battery feding back. An ideal diode would be germanium. Doubt you can buy them any more. Schottky diodes do have lower voltage drop. Just hard to find electronic parts anymore.

Better yet just unplug at the trailer connector.

Unfortunately, once our toad is all hooked up with tow shields, etc, in place, it's quite a chore to get at the cable to plug or unplug. Unplugging at the car end requires removal of the tow shield, and at the MH end removal of the bikes on the bike rack. Also some acrobatic skills are required that are beyond my old bones. We try to have the toad all hooked up the night before we leave, just to make departure easier. So, it's connected overnight before we roll.

As far as the relay, I'll have that explored next time we get near our regular RV service facility. Hooking up a diode I can probably handle myself. Not sure about a relay.

Thanks

al

Why not just add a relay to your charge circuit that only operates when the motorhome is running and opens the circuit to the toad when the motorhome is not running? Maybe a solid state battery isolator would work if you really want to use diodes but keep in mind that you will lose about .5 volt thru the diode. Better yet just unplug at the trailer connector.