Voltage vs. PWM controller & wire size

Calkidd wrote:
Someone mentioned with the higher voltage it was better to go with a MPPT controller rather than a PWM. But why?

Because PWM output = 14V*Isc.
28V*7A comes in, but only 14V*7A comes out -> 50% loss of power. If you want 24V input with PWM, you must have 24V battery bank. In your case 24V bank won't work well because your panels are a bit low in voltage

I know some will say the MPPT handles the extra voltage and turns it to amperage. HUH?

Yes. MPPT output = array wattage /battery voltage. Minus some losses in the controller.

Regardless of what voltage is going into the controller it will come out at 14.4 - 14.8 volts. Right? Thus ohm's law says my system amperage, on a perfect day, would produce 28 amps out from the controller, no?

Right, the output is 14.4-14.8V.
No, not 28A with PWM because PWM will output Isc, and Isc of these panels is 2*7A.
Yes, 28A with MPPT

I understand using such a higher voltage panel for 12 volt charging system is an overkill, but these panels are left over from a previous residential install I own.

This is not an overkill, this is 50% loss of power if you use PWM because you'll only get 14.8V*14A.

...For example I am using the Bogart 2030 controller with the Trimetric monitor.
With 2*28V panels you have to wire them in parallel, and your 20A PWM Bogart will output 14A @14.8V

I read Handy Bob's information...

Don't :)

if 10 ga works why in the hell are people using 8 or even 6 ga to run their solar panels when the loss is 2-5% with 10 ga?

Nobody uses 6 ga when 10 ga loss is 2%. 5% is a bit high, worth considering a thicker cable. Run your calculations for 14A@28V

Also, why are some using 1/0 ga for inverter and battery wiring?

Because 15A@120V after inverter = 150A@12V before inverter. So the battery feeds 150A to inverter - possibly 160A, with inverter losses. Usually it's MW and other kitchen gadgets. Terrible effect on the AH capacity too. Better to avoid those items on a small solar like yours.