12V from Tow Vehicle when there's solar on the trailer?

[vocoder]

Hello!

I just brought home my first RV last night. It's a 2014 Stealth 1913. It has a solar charging system to keep the battery charged. My tow vehicle is a GMC pickup that can send 12V to the trailer electrical connector at the hitch.

My question(s) - How does having the solar charger impact the use of 12V from the tow vehicle? Is there automatic switching that cuts to the 12V if it's supplied? Should I enable this 12V source?

I'd like the ability to use the truck to charge the trailer when I'm on the way to camp, especially when travelling at night.

Thanks!
Vocoder

[Stealth13]

Worry not I have the 13 version. It will charge from the truck and automatically cut the solar feed

[vocoder]

Perfect. Thanks for that information!

[Crankshaft]

Originally Posted by vocoder

Hello!

I just brought home my first RV last night. It's a 2014 Stealth 1913. It has a solar charging system to keep the battery charged. My tow vehicle is a GMC pickup that can send 12V to the trailer electrical connector at the hitch.

My question(s) - How does having the solar charger impact the use of 12V from the tow vehicle? Is there automatic switching that cuts to the 12V if it's supplied? Should I enable this 12V source?

I'd like the ability to use the truck to charge the trailer when I'm on the way to camp, especially when travelling at night.

Thanks!
Vocoder

I don't know the answer to your question because I do not have a solar setup (yet). I do know that your TV will NOT charge your RV battery but it will "maintain" the charge in the battery. If your RV battery is half charged your TV will keep it that way as you drive but will do no good if just plugged in and the aternator not running until the engine is started. Perhaps if you drove thousands of miles the TV will raise the charge in the RV battery. Just look at the battery cable size in the TV...6-4 guage. The "wire" going to the rear fo the TV plus the length of wire going to the RV battery would have to be 2 guage to carry enough amperage to accually charge the RV battery. It's amperage that charges the battery...not voltsage. The wire for maintaining the RV battery is 12 guage at best. So with this in mind, I would think your solar system would be more reliable to raise the charge of the battery while in motion.

[garbonz]

I see no reason why there would be any reason for this to be a problem. As stated above the vehicle system will not provide much charge to the battery in the TT as it is determining it's charging situation from the vehicle battery and that battery will be close to full charge. The solar system regulator will be looking to the TT battery voltage to determine whether and or how much to charge, even if some current is coming from the vehicle. You could have both systems going at once and that wouldn't hurt anything, I don't think. Once the system is at 14.4 volts in it's bulk charge mode, it will taper amps to keep it there until the amperage drops to a few amps, then go to float.

The answer is a bit more complex than that, but that is the gist of it.

[Stealth13]

Guess I just didnt want to get in depth
The point was that the solar regulator will , regulate how much power comes from the panel to the batteries, no matter it the TV is connected or not.

[Broadway Joe]

I beg to differ with the conclusion that you need 2 gauge to charge the tt battery. A car truck etc uses heavy cables to provide the starting cuurent needed. 12 ga wire over a 20 ft distance is recommended to carry as much as 24 amps without overheating, which is more than you would get out of an external battery charger

My $.02

[Stealth13]

I was going to say have a look at most 2A chargers , they are no where near 2 or 4 gauge for that matter but......
I thought better of it

[dustman_stx]

Originally Posted by joenic53

I beg to differ with the conclusion that you need 2 gauge to charge the tt battery. A car truck etc uses heavy cables to provide the starting cuurent needed. 12 ga wire over a 20 ft distance is recommended to carry as much as 24 amps without overheating, which is more than you would get out of an external battery charger

My $.02

You would be correct. The heavy gauge wire is only to feed the starter. Take a look at the wire going from the alternator to the battery where truck charging is taking place. That is probably either 8 or 10 gauge, depending on the amperage rating of the alternator.

[garbonz]

Wire Size and Ampacity
Even the experts have to check occasionally on the correct gauge and ampacity (maximum amount of electrical current a conductor can carry) of wire for a given marine DC load. The simplest method we’ve found uses the charts below.

Select either the 10% (Marine Wire 1) or 3% (Marine Wire 2) voltage drop chart, based on the type of load you are running.
Next, find the current consumption of the load on the vertical axis of the chart.
Find the length of the circuit on the horizontal axis of the chart, noting that the length is the “round trip” distance from the panel or battery to the load and back.
The color of the graph at the intersection (Marine Wire 3) denotes the gauge of wire to use.

Of particular interest is the equation:
Voltage Drop = Current x Length x Ohms per foot

This simple equation allows you to calculate the voltage drop for a circuit of any length and any current flow, if you know the resistance of the wire.

Finally, note that the amp capacity of the wire curtails using very short lengths of wire for large current flows, as show by the “flat tops” of the 10% chart areas.

Marine Wire Marine Wire
Wire Gauge Color Code
Colors in above charts correspond to AWG wire sizes below:

Marine Wire
These simple, proprietary graphs assume:

[garbonz]

Wire Size and Ampacity
Even the experts have to check occasionally on the correct gauge and ampacity (maximum amount of electrical current a conductor can carry) of wire for a given marine DC load. The simplest method we’ve found uses the charts below.

Select either the 10% (Marine Wire 1)or 3% (Marine Wire 2) voltage drop chart, based on the type of load you are running.
Next, find the current consumption of the load on the vertical axis of the chart.
Find the length of the circuit on the horizontal axis of the chart, noting that the length is the “round trip” distance from the panel or battery to the load and back.
The color of the graph at the intersection (Marine Wire 3) denotes the gauge of wire to use.

Of particular interest is the equation:
Voltage Drop = Current x Length x Ohms per foot

This simple equation allows you to calculate the voltage drop for a circuit of any length and any current flow, if you know the resistance of the wire.

Finally, note that the amp capacity of the wire curtails using very short lengths of wire for large current flows, as show by the “flat tops” of the 10% chart areas.

Marine Wire Marine Wire
Wire Gauge Color Code
Colors in above charts correspond to AWG wire sizes below:

Marine Wire
These simple, proprietary graphs assume:

[garbonz]

Whoops, here are the charts.

So for a maximum load of say 40 amps at a 3% loss and 20 feet of wire, you would want a wire of 6 gauge to do that.

Where this really comes into play is when you install a inverter and start talking about REALLY high currents.