Powering battery from the tow vehicle

[BigRockSpeaker]

Hi folks,

Two weeks to go until I pick up my new custom CT.  Originally, I was told that the electrical package included a 12V system that allowed the battery to be charged from the tow vehicle.  I now find out that it is charged from a shore power connection, NOT the tow vehicle - that would be extra wiring for an extra charge.  So now I'm doing research on installing that - battery isolators, etc.

Has anyone done that?  are there older threads or articles on this site that cover that?  I'm wondering on exactly how difficult it would be, options/alternatives, etc.  I do have solar panels, but was not planning on installing them on the trailer just yet, just setting them out while camping, and if I'm travelling, I wouldn't be in one place long enough to charge them through the panels.

Any assistance would be helpful.

 

[Weight]

You can charge batteries from the tow vehicle. How well depends on the strength of the alternator, but more on the gauge of the cables back to the trailer. Small AWG cables will drop voltage to the point of no charge. This is a decent auto-combiner. ; https://shop.marinehowto.com/products/blue-sea-7610-automatic-combining-relay

 

[Trebor English]

The main problem is the long distance from the tow vehicle alternator to the battery in the trailer.  Having the battery right behind the driver's seat is far enough to be a problem.  

An actual isolator is optional.  Where the tow vehicle connects to the trailerk there will be a plug that can be disconnected.  

A DC to DC charger can step up the voltage to make up for the drop of the long run.  

Since the trailer can be charged from shore power does that mean there is a battery charger?  You could have an inverter close to the tow vehicle alternator and a 120 volt extension cord to the charger.  At first glance the double conversion seems lossy.  It reduces the loss in the cable and regulates at the battery.

 

[highdesertranger]

yes the long distance is a problem but something is better than nothing. you need a 7 way trailer connector. just run the battery terminal on the 7 way like you would run a house battery. run the largest wire you can. on mine I have run 4 gauge to the connector then 10 gauge. highdesertranger

 

[John61CT]

Figure out the maximum current drawn,

ideally actually measuring, with the batt at 50% discharge, engine rpm in the mid range.

A higher-CAR batt in the future will draw more, so be conservative.

Use an online wire gauge calculator, I like Blue Sea Circuit Wizard.

One gauge A minimum for safety, a bigger one B to reduce voltage drop.

The price difference between A and B will determine whether it's worth buying a DC-DC charger to boost the voltage and give your trailer batt its own charge profile.

If not then you'll want a combiner / VSR to prevent draining your vehicle batt.

Use an appropriate sized Anderson connector in between.

Don't forget the fuse.

 

[DuneElliot]

This is something my set up is "capable" of doing but in reality the tow vehicle barely touches the charging of the batteries...too much wire that is too small to do much in reality. The cost of a solar panel and charge controller is about the same and would net you better results.

 

[web1racer]

Hi folks,

Two weeks to go until I pick up my new custom CT.  Originally, I was told that the electrical package included a 12V system that allowed the battery to be charged from the tow vehicle.  I now find out that it is charged from a shore power connection, NOT the tow vehicle - that would be extra wiring for an extra charge.  So now I'm doing research on installing that - battery isolators, etc.

Has anyone done that?  are there older threads or articles on this site that cover that?  I'm wondering on exactly how difficult it would be, options/alternatives, etc.  I do have solar panels, but was not planning on installing them on the trailer just yet, just setting them out while camping, and if I'm travelling, I wouldn't be in one place long enough to charge them through the panels.

Any assistance would be helpful.

 

[web1racer]

if you have a 12v source at the back or in your plug just put a diode in the path so that the current will only flow to the trailer

 

[John61CT]

Old-school diodes aggravate the voltage drop problem. Modern mosfet isolators that don't, cost more than a good VSR or even a low-end DCDC charger.