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Charging battery on Toad from motorhome when driving


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We have about 2,000 miles towing our Honda CRV with Blue Ox braking system and have not had any trouble with the battery running down. Will take a 5,000 mile trip in June and July with some pretty long days in mountainous terrain. Wondering what others have done to charge their toad battery from the MH. I have plenty of wire, fuse holders, and connectors so would rather purchase something that was just the minimum of components (lowest price) that will get the job done. E-trailer sells the Demco Battery Charger kit that contains a fuse and diode along with wire. Full MH voltage passes thru to the toad battery. Diodes are pretty cheap.  

I installed the wires on the CRV I would need to charge the battery when the baseplate went on.  Would probably install a fuse at both ends of the charging wire.

What are your thoughts?

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I decided to keep it simple>>> KISS.

If I drive more then 2 days I just start my Jeep and let it run for ~15-25 minutes to charge the batteries.  I actually found a routine where I start my Jeep, go and clean the windshield, and then go shut the Jeep off. 

Decided not too fool with trying to add a charge wire.

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Posted (edited)

Mike,

Check if you have a pin on the 7-pin connector that has a steady 12V feed when the engine is running. If it has you can use this (pre-wired on our Monaco). It is normally not powered with the engine off. The standard 7-to-6 pin connecting cable should make this available to the car. You will need wire this on the car side via the charger kit (several are available) and connect it to the battery.

We have had abut 3 cases where we ran our of battery power because of our own mistakes . The last one was on the road and the DW put the car in Park. The engine would not crank and we were really stranded. Jumper cables were too short and we had no way of boosting the battery. The roadside assistance was fart… around and was no help in this case. Solution for us was to start the generator and connect the portable batter charger using an extension cord (using high amps) to get the battery charged. 15 minutes later we were able to start the car and were back on the road. Thank goodness we had the charger with us.

I have seen that the Odessy battery tray will fit in the CR-V allowing you to use a larger battery. It is on my wish list.

I installed a fuse bypass switch which makes it a lot easier.

For the Patriot braking system I have a 12V cable connected to the battery to provide power. We run this and the breakaway cable under the hood and thru the window. No holes thru the firewall. Very low tech and effective.

I can provide pictures if you need any.

Edited by Martinvz
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Years ago I added a 4 pin trailer connector to my Endeavor and to my toad and made a cable to hook them together. I then connected one pin of each to the respective battery's hot terminal through a 20 amp automatic reset automotive circuit breaker. No diodes or any other active devices needed, just the circuit breakers to guard against shorts and limit the current in the cable.

 

 

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I just added a fused 12 gauge wire from my house batteries to an extra pin on the 7 pin trailer plug. On the car end run the wire from the same pin to the battery. That end should be fused also. The house batteries charge when I'm driving or on shore power so my toad battery does too. If I stop for a night with shore power and don't unhook the car I don't even bother to turn the key off because the car battery will charge with the house batteries.

I've been running it that way for the last five year an never had a problem.

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Mopar sells a tow wiring harness for jeeps that charge the battery using the stock harness. Kind of a pain to install since the plug to tie into the factory harness is up high behind the glovebox in a really tight spot.

Not sure if this is available fo other vehicles.

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The Honda towing procedure requires you to stop at least once every 8 hours and start the engine and run through the transmission prep procedure.  This should keep the battery charged.   

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Starting a car takes a pretty good amount of power. I don't believe a 5 minute run at idle will put all that back in.

Unwrapped the trailer connector and wires  at the rear of the motor home. 7 pin connector with 4 wires, left and right turn/stop coming from a Brite Lite module, tail lights, ground. Coming from the chassis wiring up stream of the Brite Lite is a "square" (really rectangular) 2 column by 3 row, 6 pin connector. Ground, left turn, right turn, stop, marker. Only one spare pin that has about a 12" pig tail. Looked on line and this is not wired at all like the "industry standard". Tried all positions of the ignition switch and could not get power to that pin. I have a several searchable copies of 2004-2006 wire diagrams that include the Scepter. Only two matches come up for "trailer". They are page 43 of my document, drawing number 38041505. One is talking about cutting a wire on one coach model, no help. The other is on the left side about midway down, level 6. The wiring to the trailer plug on this drawing shows the turn and brake combined for each side. That does not seem to be how mine is wired.  I does include a wire for the back up light. I did not have a way of testing if that is what the 6th pin is. Will have wife put MH in reverse next time we are there together. Plenty of pins in the 7 pin connector going to the CRV. I have 15 amp circuit breakers on order. If I can not find a ignition switched circuit, I will wire to the engine battery with a switch and CB. 

Also ordered a small stick on rocker switch with 39" wire pigtail. Good video on U-tube were they used pliers to cut the plastic off the top of a blown fuse and soldered wires to the two pins.  Will add a fuse holder in the pigtail. $10 bucks verses $60 for pre-made. Will be pretty simple and very reversible when we sell the car.

If anybody has different wiring diagrams, I would sure like to see how this is really wired.

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Posted (edited)

This is how mine is wired, pic from my notes, looking at MH side of the cable from my Jeep. Installed a 10A breaker in RRB and a diode with fuse at the battery since the charging wire is not a big gauge. It's got a separate lead for the brake so I use a converter box for that US style rear lights.

20220505_154246.jpg

Edited by Ivan K
Corrected cable side description...
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On 5/4/2022 at 3:16 PM, JDCrow said:

I went with RVI and it was any easy install and works great 

 

https://rvibrake.com/collections/flat-towing-products/products/towed-battery-charger-plus

X2 with RVI.  At first I installed a fused line from the MH to the toad. After doing so, I was concerned that if there was a problem with the MH charge system it would drain the toad battery and I would be stuck on the side of the road with 2 dead vehicles. Purchased a "Toad Battery Charger" from RVI and have not had any problems keeping the toad battery fully charged.

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6 hours ago, veraken said:

X2 with RVI.  At first I installed a fused line from the MH to the toad. After doing so, I was concerned that if there was a problem with the MH charge system it would drain the toad battery and I would be stuck on the side of the road with 2 dead vehicles. Purchased a "Toad Battery Charger" from RVI and have not had any problems keeping the toad battery fully charged.

If there is  problem with your MH charging system the "Toad Battery Charger" won't charge your toad. I think all it has over a direct wire system is some indicator lights and maybe a diode.

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16 hours ago, Tom Wallis said:

If there is  problem with your MH charging system the "Toad Battery Charger" won't charge your toad. I think all it has over a direct wire system is some indicator lights and maybe a diode.

My concern was that the motorhome would drain the battery.  The RVI will help prevent that from happening. 

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Most of the charging devices are one way 12V flow with diodes to prevent the coach from draining the car battery.

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I know each system is different…

I use RVIBrake. It needs a 12v. I have a Jeep JK - so nothing needs done on the Jeep (electrically).
to power the RVIBrake, I first got a Battery jump start kit that had a 12v socket on it. That worked fine for a few years. 
 

I recently made a 12v 50ah lithium battery in a Harbor Freight “Pelican” case. It also has a 12v socket (plus a light, usb, and power pole connectors).  That works very well for me. 

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  • 2 weeks later...

Tested my 12v connection from MH to CRV. Old blue spiral 6 pin to 7 pin cable rubber deteriated so purchased new Hopkins yellow cable with LEDs. Just long enough. When I installed my FASS pump, I installed a Blue Sea fuse block off chassis battery and ground bus bar in rear battery compartment. Ran wire from fuse block to 7 pin trailer connector thru 20 amp fuse and 14 ga wire. Thru spiral cable to 6 pin of front of CRV. From 6 pin connector thru 15 amp breaker to + post on battery. Ground thru 6 pin also to neg on battery and from 7 pin to frame of the MH. With spiral cable connected, MH engine running at 13.8 volts, I had 1.5 amps feeding into CRV battery. Will continue to monitor but pleased with the overall way the system is working.  

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