Reworking wiring on portable solar kit (1 Viewer)

[Phoenix David]

Bought an Acopower 105W (5.8 amps rated) folding solar kit off Amazon for my dual battery system in my 09 Tacoma. I usually drive daily when i'm out, but wanted back up for some longer more remote trips coming up.

The Acopower works fine in my test. But the controller is two feet from the panel with the 10 ft extension to the battery and I'd like a longer reach. The cables are 14awg. As is, it puts out up to 14v in my test, aimed directly at the 2pm sun, and the PWM controller seems OK. I gather from researching threads here and Expedition Portal that the controller is placed too close to the panel to be efficient. I'll just use it like this for a near term trip and see, but I want to reverse the controller position and extend the cable. I'd like to get a bit more out of the setup for the absorbtion phase if possible.

Since the first two feet of wiring from the panel to an MC4 connector to the controller is not easy to replace, does replacing the 10ft 14awg cable with a 20ft 10awg to the controller buy me any minor improvement if I keep the first two feet of 14awg? Seems like I'd want the least resistance regardless, though, right?

Also, is there much lost with adding an additional connector? Thinking of replacing the clamps with Anderson connectors and a permanent cable from the battery. I know an MPPT controller would add some efficiency, but I gather that's limited with just a 105w panel, right?

 

[spressomon]

What is the measured voltage at the panel?

 

[george_tlc]

It is preferable to have the controller as close to the battery as possible. The voltage drop from controller to battery is not something the controller can compensate for - so keeping that voltage drop as low as possible will help the controller sense and maintain the charging voltage profile with more accuracy.

To determine your wiring loss all you need to know is the current that is flowing from the controller to your battery.

V = I * R (voltage = Current * Resistance).

If you know the current (or measure it) then all you need to know is the Resistance of your wire.

American Wire Gauge Chart and AWG Electrical Current Load Limits table with skin depth frequencies and wire breaking strength gives you the ohms per 1000'. Measure the wire length from your controller to your battery (remember to ADD the length of the positive wire run to the length of the negative wire run). Then calculate the resistance of the wiring.

Then you can calculate your voltage drop and determine if moving the controller is better than moving to a heavier cable...

MPPT will give you some gain on a 100W panel. Whether that gain is worth the $ is your decision.

cheers,
george.

 

[Phoenix David]

Thanks for the feedback. I'm pretty sure I'll both move the controller and extend with a heavier cable. I'm eyeing that Victron Mppt controller with the BT app too. I'm going to end up with more solar capacity in the near future for a trailer so it would serve well.

Can I measure the panel output without having it hooked up to a battery or load? I thought that wasn't good for the panel, though not sure why. If so, I guess just stick the meter probes into the MC4 connectors?

 

[george_tlc]

Panel doesn't care if there isn't a load. If that wasn't the case they would need to ship panels with a light proof cover until connected up

With no load, you really aren't measuring anything useful at the panel other than open circuit voltage which will likely be somewhere near 18 - 22V for a nominal '12V panel'.

cheers,
george.