Need advice on 50 ft cable to portable solar panel

[profdant139]

We have a 120 watt portable solar panel -- it almost always generates enough power to top off our battery every day.

We usually park the trailer in the shade and put the panel in the sun. We have a 30 foot cord -- heavy gauge (I think 12 gauge). Very little voltage drop.

But there are times when we wish we had a longer cable -- 50 feet would do the job for sure.

So that is my question – I know that a ten gauge cable would be ok, but it is thick and heavy and awkward to deal with. Would a twelve gauge cable cause a significant voltage drop? Are there reference tables that indicate how much of a drop is caused by a cable of X gauge at Y feet?

Thanks in advance for your expertise!

[Bobbo]

profdant139 wrote:
I am going to display my ignorance here, so be ready to laugh. How do I tell what kind of controller I have?? It is built in to the portable panel -- but I bet I could un-attach it, with enough brute force. 😉

I'd be willing to bet it is PWM since it came on the panel. My recommendation, get a good MPPT (I chose Victron SmartSolar) and put it at the batteries. Then disconnect your panels from the OEM controller and run them directly to the MPPT controller.

One caveat. I have not been able to find a good weatherproof MPPT controller. You will need to protect it if it is going to be exposed to the elements.

[jaycocreek]

What portable solar panel do you have?

[profdant139]

I am going to display my ignorance here, so be ready to laugh. How do I tell what kind of controller I have?? It is built in to the portable panel -- but I bet I could un-attach it, with enough brute force. 😉

[jaycocreek]

I don't think you will notice any difference,the way there aimed is far more important for incoming amps/watts...

Two 100 watt portable panels laying flat on my truck camper roof..



Minutes later,standing on the roof aimed at the sun..

[ktmrfs]

time2roll wrote:

profdant139 wrote:
Very interesting points about moving the controller -- I will have to experiment with that to see how much difference it makes.

Panel is probably 18 to 22 volts and is cut to 14.x at the controller.

If the 18 volts drops to 15 through the wire to the controller it may not matter much as the controller will still put 14.x on the battery.

If the controller is at the panel you have 14.x going through the long wire and limiting power to the battery.

for a PWM controller at the battery, as long as voltage drop doesn't get down to below around 15V drop will have almost no effect on charging current. For a MPPT controller output may drop some due to the power loss in the cable that the MPPT controller normally could use. Worst case MPPT controller will end up delivering the same power as a PWM controller when the voltage drop gets big enough.

[time2roll]

profdant139 wrote:
Very interesting points about moving the controller -- I will have to experiment with that to see how much difference it makes.

Panel is probably 18 to 22 volts and is cut to 14.x at the controller.

If the 18 volts drops to 15 through the wire to the controller it may not matter much as the controller will still put 14.x on the battery.

If the controller is at the panel you have 14.x going through the long wire and limiting power to the battery.

[Tom_M1]

ktmrfs wrote:
buy a 12Ga 3 wire extension cord, cut the ends off it and solder the green wire to either the black or white on one end do the same at the other end soldering to the same color you did at the first end.

Another approach is to make adapter plugs to go on each end and jumper the wires at the adapter. This way you have a dual purpose cable. Remove the adapters and use it as a regular 120 VAC extension cord.

[2112]

How about making a 20ft 10AWG extension cable. Place your panel where you want it. Add the extension if the existing 30ft doesn't reach the camper.

Do you have a PWM or MPPT controller?

[profdant139]

Very interesting points about moving the controller -- I will have to experiment with that to see how much difference it makes.

[time2roll]

I would get some #10 and accept what it is. You may not get full power but certainly more than fighting the shade.
Controller should be near the battery.

[Mike134]

Buy plain old 10ga stranded wire cut 2 50' pieces tape them together every 3 feet.
Your only dealing with a 12 volt circuit.

That's how we used to string temporary lights till they changed the NEC and required an outer jacket over the conductors.

[ktmrfs]

buy a 12Ga 3 wire extension cord, cut the ends off it and solder the green wire to either the black or white on one end do the same at the other end soldering to the same color you did at the first end. you now have a cable with 1 conductor 12ga and the other 10ga. total resistance will be about 0.13 ohms. voltage drop with 5A will be about 0.6V

and an easy way to do a group of cables is to use anderson connectors on both ends. that way you could make the 50ft two 25ft real easy and plug and play to go to whatever length you want.

BTW the 0.6V drop won't have much of an effect.

Or the big kanuna option is to get 30ft of 30A trailer cords and do the same trick. but now you have one conductor at 10 ga and the other at 8Ga

for each 30ft section you would have only a 1/4V drop not enough to worry about.

I have close to 120ft of cable made this way with anderson connectors to string whatever length I need.

FWIW I have three 160 W portable panels going to an MPPT controller and using the 30A cords wired as described. Usually panels in series to minimize drop. a 100W panel would be no problem.

NOW THE BIG THING YOU MUST PAY ATTENTION TO. The controller MUST be at the battery end, NOT at the panel end!. Otherwise the controller will output a voltage it expects the battery to see and the voltage drop will mess up the charging rate big time. And NOT in the direction you want. Charging current will drop like a rock, even 1/4V will really drop the charging rate. If the controller is on the panel, remove it, make a panel board or some way to place it even temporarily within a few feet of the battery so the cable goes from the panel to the controller, not from controller to battery.

[profdant139]

Lots of good tips so far -- keep 'em coming! I had not thought about welding cable -- I bet that is available at Harbor Freight -- they have a whole welding aisle.

[red31]

Luckily the panel operates over a wide range of voltages.

I use 12g landscape wire